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Leprechaunism features a clinical constellation characterized by extreme insulin resistance, growth retardation, and several distinct developmental abnormalities. One puzzling observation about leprechaunism is that mutations in the insulin receptor gene frequently associated with this syndrome cannot account for the aberrant responses of cultured cells to other growth factors. Here we report that the generation of reactive oxygen species (ROS) is impaired in cells from leprechaunism patients, thus shedding new light on this issue. Stimulation of patients’ skin fibroblast cells with platelet-derived growth factor (PDGF) resulted in a lower-level tyrosine phosphorylation of cytosolic proteins compared with that seen in normal cells. In addition, consistent with the hypothesis that ROS mediate the level of tyrosine phosphorylation of cytosolic proteins through inactivation of protein tyrosine phosphatases (PTPases), patient fibroblast cells showed a significantly higher phosphatase activity than normal cells. We further showed that the lower-level tyrosine phosphorylation in response to growth factors results from the downregulation of an NADPH oxidase, Nox4, which in turn results in the reduction of ROS generation. Ectopic expression of Nox4 in the patient fibroblast cells consistently restored PDGF-induced ROS production and regulation of PTPase activities. Taken together, these data provide insight into the mechanisms through which growth retardation is associated with leprechaunism syndrome.

Recombinant methionyl human leptin (r-metHuLeptin) therapy has shown clear efficacy in the treatment of severe insulin resistance associated with lipodystrophy syndromes and low leptin levels. We treated two siblings with Rabson-Mendenhall syndrome (severe insulin resistance and presumed insulin receptor mutations). The brother and sister, aged 13 and 11 yr, respectively, had severe acanthosis nigricans, insulin resistance, and diabetes. Both were taking 2000 mg metformin and 2 mg rosiglitazone daily; the brother was also taking 300 U regular insulin daily. In contrast to our lipoatrophic patients treated with r-metHuLeptin, these two patients had a higher percent body fat and low-normal fasting triglycerides [42 mg/dl (0.37 mmol/liter), male sibling, and 33 mg/dl (0.47 mmol/liter), female sibling]. The siblings were treated with r-metHuLeptin therapy for 10 months and demonstrated a 40-60% decrease in fasting serum glucose and insulin levels and improved glycosylated hemoglobin. There was corresponding improvement in glucose and insulin tolerance during leptin therapy. This is the first report of a partial, but significant, effect of r-metHuLeptin administration in patients with extreme insulin resistance with a presumed insulin receptor mutation and low serum triglyceride levels.

We analyzed the insulin receptor gene in four patients with leprechaunism and one with type A insulin resistance. We detected novel and previously reported mutations. The novel mutants were expressed in Chinese hamster ovary cells to evaluate the consequences for insulin receptor function. A type A insulin resistance patient from Morocco was homozygous for Arg252His mutation, similar to a previously described type A patient from Japan. A patient with leprechaunism was homozygous for the Ser323Leu mutation, previously identified in homozygous form in two patients with Rabson-Mendenhall syndrome. Phenotypic expression of this mutation is variable. A patient with leprechaunism is compound heterozygous for the previously described Arg1092Trp mutation and a nonsense mutation in codon 897. Another patient with leprechaunism was homozygous for a novel Asn431Asp mutation, which only partially reduces insulin proreceptor processing and activation of signaling cascades. The novel Leu93Gln mutation that fully disrupts proreceptor processing was found in one allele in a patient with leprechaunism. A nonsense mutation at codon 1122 was in the other allele. These results expand the number of pathogenic insulin receptor mutations and demonstrate the variability in their phenotypic expression. The biochemical analysis of mutant insulin receptors does not reliably predict whether the phenotype will be leprechaunism, the Rabson-Mendenhall syndrome, or type A insulin resistance. The previously reported correlation between fibroblast insulin binding and duration of patient survival was not observed.

The insulin receptor is a ligand-activated tyrosine kinase. Mutations in the corresponding gene cause the rare inherited insulin-resistant disorders leprechaunism and Rabson-Mendenhall syndrome. Patients with the most severe syndrome, leprechaunism, have growth restriction, altered glucose homeostasis and early death (usually before 1 year of age). Rabson-Mendenhall syndrome is less severe, with survival up to 5-15 years of age. These disorders are transmitted as autosomal recessive traits. Here we report six new patients and correlate mutations in the insulin receptor gene with survival. Patients with leprechaunism were homozygous or compound heterozygous for mutations in the extracellular domain of the insulin receptor and their cells had markedly impaired insulin binding (10% of controls). Mutations in their insulin receptor gene inserted premature stop codons (E124X, R372X, G650X, E665X and C682X), resulting in decreased levels of mature mRNA, or affected the extracellular domain of the receptor (R86P, A92V, DeltaN281, I898T and R899W). Three patients with Rabson-Mendenhall syndrome had at least one missense mutation in the intracellular domain of the insulin receptor (P970T, I1116T, R1131W and R1174W). Expression studies in CHO cells indicated that the R86P, A92V, DeltaN281, I898T, R899W and R1131W mutations markedly impaired insulin binding (5% of control), while the P970T, I1116T and R1174W mutant receptors retained significant insulin-binding activity. These results indicate that mutations in the insulin receptor retaining residual insulin-binding correlate with prolonged survival in our series of patients with extreme insulin resistance.

To the Editor: Insulin resistance is a common precursor to type 2 diabetes mellitus. It is characterised by impaired insulin signalling in several tissues, with compensatory hyperinsulinaemia. Extreme insulin resistance, on the other hand, is very rare. Although the molecular basis for extreme insulin resistance remains unknown in many patients, lipodystrophies and loss-of-function mutations in the insulin receptor gene are well established causes of this phenotype. In patients with lipodystrophy, type 2 diabetes is usually associated with several metabolic disturbances, including low HDL-cholesterol, hypertriacylglycerolaemia and non-alcoholic fatty liver disease, among others [1]. Mutations in the insulin receptor gene produce a spectrum of diseases including Donohue’s syndrome, Rabson–Mendenhall syndrome and type A insulin resistance; patients with these conditions have several different characteristics [2]. Severe cases are diagnosed at birth or in infancy due to the presence of signs of severe hyperinsulinaemia such as acanthosis nigricans, abnormal dentition, hyperandrogenism and pseudo-acromegaly. Type 2 diabetes develops early in life and its treatment is usually extremely challenging. Insulin is often used in very high doses, but microvascular complications develop early and aggressively in these patients [2, 3]. The use of other therapies (leptin, IGF-1, metformin and pioglitazone) has already been described in scattered reports, but usually as monotherapy and with limited efficacy [4]. A 17-year-old boy was brought to our attention for treatment of type 2 diabetes. His BMI was in the ageand sex-specific normal range (weight 44.8 kg, height 161.0 cm) and he had no lipodystrophy. He was the older son of non-consanguinous parents and his development was unremarkable except for abnormal dentition and short stature. He had had a history of severe acanthosis nigricans since 6 months of age affecting cervical, axillary and inguinal areas, and macrogenitalism without macro-orchidism had been diagnosed in early life. On examination he had signs of pseudoacromegaly and hyperandrogenism. Initial fasting glucose and insulin were 6.8 mmol/l and 2,102 pmol/l, respectively, with postprandial glucose (at 2 h) of 23.5 mmol/l. Postprandial insulin was above the laboratory limit of detection. Fasting triacylglycerol and HDL-cholesterol were normal at 0.56 mmol/l and 1.0 mmol/l, while HbA1c was 11.9%. On clinical and biochemical grounds type 2 diabetes secondary to Rabson–Mendehall syndrome was diagnosed. Sequencing of the insulin receptor gene revealed two mutations: (1) Asn851Ser, a novel mutation changing an exquisitely conserved residue in one of the extracellular FnIII domains of the beta subunit of the receptor; and (2) the previously described Ala1135Val in the highly conserved catalytic loop of the tyrosine kinase domain of the receptor [5]. R. O. Moreira (*) :R. L. Zagury : L. Zagury Instituto Estadual de Diabetes e Endocrinologia, Rua Moncorvo Filho 90, Rio de Janeiro, RJ, Brazil e-mail: rom_br@yahoo.com

Leprechaunism is an inherited insulin resistance syndrome,caused by homozygous or compound -heterozygous mutations in the insulin receptor gene. Preimplantation genetic diagnosis (PGD) is an early form of prenatal diagnosis. Donohue syndrome is a very rare but fatal genetic disorder .A family with four children were diagnosed with Donohue syndrome, three of them were born at term and lost around 5 months of age,and one was diagnosed by amniocentesis and terminated by abortion. By PGT we obtained a healthy baby.Our aim is to report the first case of Donohue syndrome diagnosed after performance of preimplantation genetic diagnosis (PGD) in Turkey.

Leprechaunism is the most severe form of insulin resistance, manifesting with abnormal glucose metabolism and retarded growth. In the present study, we investigated the biological actions of recombinant human insulin-like growth factor I (rhIGF-I) in fibroblasts derived from a patient with leprechaunism. In the same patient, we also investigated the pharmacokinetics of IGF-I and the long-term effect of rhIGF-I treatment on metabolic control and physical growth. The patient’s fibroblasts showed normal binding of IGF-I, normal phosphorylation of the β-subunit of the IGF-I receptor, and normal[ 3H]thymidine incorporation in response to IGF-I. The fibroblast studies suggested that the patient would respond to IGF-I therapy, but certainly did not exclude the possibility of IGF-I resistance in vivo. Administration of recombinant human GH at the dose of 2.0 IU/kg for 3 consecutive days induced a minimal response of serum total IGF-I and IGF-binding protein-3 (IGFBP-3), suggesting partial GH resistance. To increase the serum total IGF-I level, we administered rhIGF-I with combination therapy of intermittent and continuous sc injection. This sustained the serum total IGF-I level, but not the serum IGFBP-3 level, within the normal range. The patient was treated with combination therapy of rhIGF-I by both sc injection and continuous sc infusion for 6 yr and 10 months. Administration of rhIGF-I at total daily dose of 1.6 mg/kg maintained her growth rate and hemoglobin A1c level nearly within the normal range. These findings suggest 1) that this leprechaun patient has an IGF-Ideficient state and partial GH resistance, as reflected by impaired production of IGF-I and IGFBP-3; 2) that rhIGF-I treatment works effectively for preventing postnatal growth retardation and normalizing glucose metabolism in patients with extreme insulin resistance; 3) that this treatment requires relatively higher dose of rhIGF-I; and 4) that treatment appears to be safe and devoid of adverse effects.

We report a homozygous missense mutation at position 1092 (substitution of glutamine for arginine) in the tyrosine kinase domain of the insulin receptor in a patient with leprechaunism associated with severe insulin resistance and intrauterine growth retardation. Site-directed mutagenesis as well as analyses of the patient's lymphocytes revealed that this mutation causes a marked decrease in tyrosine kinase activity of the insulin receptor without any defect in insulin binding, which causes severe defects in insulin-stimulated glucose transport, glycogen synthesis and DNA synthesis. Thus, this is the first homozygous mutation resulting in a selective-kinase defect of the insulin receptor. Interestingly, the parents who are cousins and are heterozygous for the mutation have type A insulin resistance syndrome. This correlation between genotype and phenotype in a single pedigree suggests that the severity of the mutation will determine the phenotype. Based upon this assumption, we have been successful in prenatal diagnosis of the fifth child. Furthermore, we have demonstrated the effectiveness of clinical administration of insulin-like growth factor-I (IGF-I) in this patient and in vitro analysis of the patient's skin fibroblasts, suggesting that IGF-I can compensate for insulin action via the IGF-I receptor in a patient almost lacking functional insulin receptors.

Rabson-Mendenhall syndrome (RMS) is a rare syndrome manifested by extreme insulin resistance with hyperinsulinemia, acanthosis nigricans, tooth dysplasia and growth retardation. Our patient was first noted at the age of 8 months due to pigmentations on skin-folded areas. Initial laboratory tests showed normal fasting glucose (69 mg/dL). Fasting insulin level was severely elevated, up to 554.6 µIU/mL, and c-peptide level was increased, up to 13.81 ng/mL. However, hemoglobin A1c was within normal range (4.8%). He is now 11 yr old. His growth development followed the 5-10th percentile and oral hypoglycemic agents are being administered. The last laboratory results showed insulin 364.1 µIU/mL, C-peptide 4.30 ng/mL, and hemoglobin A1c 7.6%. The boy was a compound heterozygote for the c.90C > A and c.712G > A mutations of the insulin receptor gene, INSR, which are nonsense and missense mutations. In summary, we report the first Korean case of RMS, which was confirmed by two novel mutations of the INSR.

Rabson-Mendenhall syndrome is a rare, autosomal recessive disorder affecting insulin receptor. This disorder is characterized by insulin-resistant diabetes mellitus, hyperinsulinemia, deficiency of subcutaneous fat, acanthosis nigrican, growth retardation, coarse and senile appearance, precocious puberty, and dental prematurity, enlarged genitalia, and pineal hyperplasia. Mutations of the insulin receptor gene affecting insulin action appear to be the basic mechanism underlying this syndrome. Herein, we present a case report on Rabson-Mendenhall syndrome in a 9-year-old girl.

Homozygous inactivation of a gene, as is frequently performed to generate mouse models, provides an opportunity to elucidate the role that the gene plays in normal physiology. However, studies of human disease provide direct insight into the effect of inactivating mutations in man. In this investigation, we have identified a one year-old boy from a consanguineous pedigree who is homozygous for deletion of the insulin receptor gene resulting in leprechaunism. Contrary to previous predictions, the complete deletion of the insulin receptor gene is compatible with life.

Insulin resistance contributes to the pathogenesis of NIDDM. We have investigated the molecular mechanisms of insulin resistance in patients with genetic syndromes caused by mutations in the insulin-receptor gene. In general, patients with two mutant alleles of the insulin-receptor gene are more severly insulinresistant than are patients who are heterozygous for a single mutant allele. These mutations can be put into five classes, depending upon the mechanisms by which they impair receptor function. Some mutations lead to a decrease in the number of insulin receptors on the cell surface. For example, some mutations decrease the level of insulin receptor mRNA or impair receptor biosynthesis by introducing a premature chain termination codon (class 1). Class 2 mutations impair the transport of receptors through the endoplasmic reticulum and Golgi apparatus to the plasma membrane. Mutations that accelerate the rate of receptor degradation (class 5) also decrease the number of receptors on the cell surface. Other mutations cause insulin resistance by impairing receptor function—either by decreasing the affinity to bind insulin (class 3) or by impairing receptor tyrosine kinase activity (class 4). The prevalence of mutations in the insulin receptor gene is not known. However, theoretical calculations suggest that ∼0.1–1% of the general population are heterozygous for a mutation in the insulinreceptor gene; the prevalence is likely to be higher among people with NIDDM. Accordingly, it is likely that mutations in the insulin-receptor gene may be a con-tributory cause of insulin resistance in a subpopulation with NIDDM.

A 2-month-old girl presented with increasing abdominal girth and failure to thrive. Pelvic US showed an enlarged right ovary containing multiple cysts (Fig. 1). The left ovary appeared the same. A slightly enlarged uterus with pubertal configuration and prominent endometrium is also shown (Fig. 2, arrows). Dr. William Donohue of the Hospital for Sick Children in Toronto first reported leprechaunism (also known as Donohue syndrome) in 1954. Physical features included growth retardation, lipoatrophy, acanthosis nigricans, hypertrichosis, abnormal facies, breast tissue hyperplasia, and enlarged genitalia. Endocrine dysfunction was suggested by abnormal glucose levels and profound insulin resistance. Autopsies revealed pancreatic islet cell hyperplasia and cystic ovaries [1].

Objective To evaluate renal structure in a child with Donohue syndrome (leprechaunism), who at 10 yr of age was noted to have hypertension, microalbuminuria, and enlarged kidneys, a renal biopsy was performed. Research Design And Methods The renal biopsy tissue was evaluated by light and electron microscopy with standard stereological techniques to measure glomerular volume, glomerular basement membrane width, fractional mesangial volume, and peripheral capillary filtering surface density. Results On renal biopsy, there was a marked increase in glomerular volume, glomerular basement width, and mesangial volume, findings similar to those seen in patients with diabetic nephropathy. Conclusions This patient with marked insulin resistance associated with Donohue syndrome demonstrates renal and glomerular enlargement and morphometric glomerular changes similar to those seen in patients with diabetic nephropathy. In unusual syndromes with hyperglycemia and hyperinsulinemia, renal structural and functional changes typical of traditional diabetes mellitus may be seen.

The nucleotide sequence was determined for all 22 exons of the insulin receptor gene from three patients with genetic syndromes associated with extreme insulin resistance. In all three patients, insulin resistance was caused by decreased insulin binding to the cell surface. The patient with leprechaunism (leprechaun/Winnipeg) came from a consanguineous pedigree and was homozygous for a missense mutation substituting arginine for His209 in the alpha-subunit of the insulin receptor. The other two patients were both compound heterozygotes with a nonsense mutation in one allele of the insulin receptor gene, and a missense mutation in the other allele. In the patient with the Rabson-Mendenhall syndrome (patient RM-1), the missense mutation substituted lysine for Asn15 in the alpha-subunit. In the patient with type A extreme insulin resistance (patient A-1), the missense mutation substituted serine for Asn462 in the alpha-subunit. Both nonsense mutations markedly reduced the levels of insulin receptor mRNA transcribed from the alleles with the nonsense mutation as compared to the transcripts from the other allele. The reduction in the level of mRNA would be predicted to greatly reduce the rate at which the truncated receptors would be synthesized. Furthermore, the truncated receptors would be severely impaired in their ability to mediate insulin action.

Insulin receptor complementary DNA has been cloned from an insulin-resistant patient with leprechaunism whose receptors exhibited multiple abnormalities in insulin binding. The patient is a compound heterozygote, having inherited two different mutant alleles of the insulin receptor gene. One allele contains a missense mutation encoding the substitution of glutamic acid for lysine at position 460 in the alpha subunit of the receptor. The second allele has a nonsense mutation causing premature chain termination after amino acid 671 in the alpha subunit, thereby deleting both the transmembrane and tyrosine kinase domains of the receptor. Interestingly, the father is heterozygous for this nonsense mutation and exhibits a moderate degree of insulin resistance. This raises the possibility that mutations in the insulin receptor gene may account for the insulin resistance in some patients with non-insulin-dependent diabetes mellitus.

[125I]Insulin binding has been studied in two patients with extreme insulin resistance using cultured B-lymphocytes transformed with Epstein-Barr virus. A cell line from a female infant with leprechaunism had insulin binding which was decreased 90% below the lower limit of normal. Lymphocytes from a young woman with type A extreme insulin resistance (associated with acanthosis nigricans and virilization) had insulin binding which was 80% depressed. In both cases, the defect in binding resulted from a decrease in the number of receptors per cell. The remaining receptors had normal properties, including a normal affinity for insulin and a normal specificity for insulin analogs. Insulin binding in cultured lymphocytes from these two insulin-resistant patients was also inhibited normally by antibodies to the insulin receptor. Immunological assays using anti-receptor antibodies confirmed the conclusion that the number of receptors was decreased. Affinity labeling of the leprechaun insulin receptor with [125I]insulin demonstrated the existence of an alpha-subunit with apparently normal molecular weight (130,000 daltons). However, the number of receptor molecules per cell appeared reduced.

Insulin stimulation of glycogen synthase and of thymidine incorporation into DNA has been examined in fibroblasts derived from three insulin-resistant patients: two with the type A syndrome of insulin resistance and acanthosis nigricans and one with the syndrome of leprechaunism. All three cell lines were previously shown to exhibit abnormal insulin-binding properties with alterations in receptor number or affinity. In the basal state, fibroblasts from all three patients contained normal levels of total glycogen synthase activity. Two of the cell lines, those of type A patient A-l and those of the leprechaun infant, had an abnormally high percentage of the enzyme in its glucose-6-phosphate-independent or dephosphorylated form and lower than normal cellular glycogen stores, consistent with an inverse correlation between percent I activity and glycogen content observed with other cells. Cells from patient A-3 had normal levels of glycogen and a low percentage of enzyme in the independent form. Insulin activ...

In six patients with acanthosis nigricans variable degrees of glucose intolerance, hyperinsulinemia and marked resistance to exogenous insulin were found. Studies of insulin receptors on circulating monocytes suggest that the insulin resistance in these patients was due to a marked decrease in insulin binding to its membrane receptors. When these patients were fasted, there was a fall in plasma insulin but no increase in insulin binding, suggesting that the receptor defect was not secondary to the hyperinsulinemia. The clinical features shared by these cases and several similar ones previously reported may be divided into two unique clinical syndromes: Type A, a syndrome in younger females with signs of virilization or accelerated growth, in whom the receptor defect may be primary, and Type B, a syndrome in older females with signs of an immunologic disease, in whom circulating antibodies to the insulin receptor are found.

Clinical features of 15 reported cases and one in the present study are critically analysed for evolving diagnostic criteria for leprechaunism. A tetrad of features is suggested for diagnosing this syndrome.

A point mutation in the human insulin receptor gene in a patient with type A insulin resistance alters the amino acid sequence within the tetrabasic processing site of the proreceptor molecule from Arg-Lys-Arg-Arg to Arg-Lys-Arg-Ser. Epstein-Barr virus-transformed lymphocytes from this patient synthesize an insulin receptor precursor that is normally glycosylated and inserted into the plasma membrane but is not cleaved to mature alpha and beta subunits. Insulin binding to these cells is severely reduced but can be increased about fivefold by gentle treatment with trypsin, accompanied by the appearance of normal alpha subunits. These results indicate that proteolysis of the proreceptor is necessary for its normal full insulin-binding sensitivity and signal-transducing activity and that a cellular protease that is more stringent in its specificity than trypsin is required to process the receptor precursor.

Insulin binding has been characterized on fibroblasts cultured from two patients with the type A syndrome of insulin resistance and acanthosis nigricans (A-l and A-3) and from one infant with insulin resistance associated with leprechaunism. [125I]Insulin binding was markedly decreased in cells from all three patients. The defect in insulin receptors appeared specific; binding of insulin-like growth factor I was normal. Assuming a cooperative model for the insulin receptor, the decrease in insulin binding in the cells of the leprechaun infant and of patient A-l appears to be due to a decrease in receptor affinity. In both cases, this decrease in affinity was associated with an accelerated dissociation of bound [125I]insulin and a loss of negative cooperativity, i.e. dissociation was not accelerated by the addition of unlabeled hormone. In contrast, cells from patient A-3 showed no change in affinity, but demonstrated a reduction in apparent receptor number. Multiple other abnormalities of insulin receptor...

We have studied a 2-year-old girl with acanthosis nigricans, glucose intolerance, marked hyperinsulinemia, and somatic features characteristic of the leprechaunism syndrome. Circulating plasma insulin levels were increased up to 50-fold and the patient showed a blunted hypoglycemic response to an injection of exogenous insulin (0.2 units/kg), indicating the presence of severe insulin resistance. Insulin purified from the patient's plasma was normal on the basis of chromatographic, electrophoretic, and immunologic criteria. Furthermore, the purified insulin competed effectively with 125 I-labeled insulin for binding to insulin receptors on cultured IM-9 lymphocytes and rat fat cells and also exhibited normal biological potency when tested on rat fat cells. Anti-insulin receptor and anti-insulin antibodies were not detected in the patient's plasma, and plasma levels of glucagon, growth hormone, and cortisol were normal. Insulin binding to the patient's circulating monuclear leukocytes was only slightly depressed into the low normal range and could not account for the severe insulin resistance. Studies on the patient's fibroblasts revealed normal levels of insulin receptors but a total absence of insulin's ability to accelerate glucose transport. Because rates of glucose transport and metabolism were normal in the basal state in the absence of insulin, we conclude that this patient's insulin resistance is due to an inherited cellular defect in the coupling mechanism between occupied insulin receptors and the plasma membrane glucose transport system.

Summary 1. A clinical and pathological syndromeis described to which the term “leprechaunism” has been applied. 2. The syndrome is probably thehomozygous combination of a rare recessive gene, the homozygous combination being facilitated by the consanguinity of the parents.

Summary A male infant is described who had manyof the features of the syndrome “leprechaunism”, previously described only in females and who exhibited a diffuse disturbance of tissues of mesenchymal derivation. Mental ability was seriously impaired. Growth, especially of the hands, feet, and facies, was markedly deranged. There was evidence of severe disturbance of collagen and osseous metabolism. Studies of carbohydrate metabolism, though inconclusive, suggested decreased homeostatic response to hypoglycemia. Although physical examination suggested endocrine disease involving androgenic substances, no data could be obtained to substantiate the presence of it. The skin over the hands and feet grossly resembled cutis gyrata. Low connective tissue phosphatase and serum alkaline phosphatase levels were present, but the clinical picture and the absence of phosphoethanolamine in the urine made a diagnosis of hypophosphatasia untenable in the light of present knowledge. Further metabolic studies and histochemicalinvestigation of the tissues of this infant are contemplated to elucidate further the basic pathology. It is hoped that the recording of this infant will contribute to further classification and investigation of these peculiar and fundamental defects.

Two cases of leprechaunism in sisters are described and compared with data ofother cases described previously.

Genetic forms of severe insulin resistance are often characterized by alterations in binding and/or kinase properties of the insulin receptor. To evaluate whether alterations in insulin receptor kinase of erythrocytes can be used as genetic markers, we studied patients with two apparently inherited conditions of severe insulin resistance (leprechaunism and the type A syndrome of insulin resistance) and their families. In the two propositi, [125I]insulin binding to intact erythrocytes was decreased by 64% and 45%, respectively. This was primarily due to a decrease in receptor number and was found in intact cells and solubilization of the receptors. Similar insulin binding defects were found on monocytes. Insulin-stimulated tyrosine kinase activity of the solubilized receptor from erythrocytes was also decreased and to a similar extent as binding. Parents of neither patient had clinical manifestations of leprechaunism or the type A syndrome. Furthermore, no alterations in insulin receptor binding or kinase activity were found in erythrocytes from the mothers. Insulin binding in the father of the type A patient was also normal, whereas the father of the leprechaun had decreased receptor affinity. Receptors extracted from the both fathers' cells had a 40-60% decrease in maximal insulin-stimulated phosphorylation and significant rightward shifts of the insulin dose-response curves (ED50, 141 and 42 ng/mL, respectively; control ED50, 16 ng/mL). The finding of biochemical defects in insulin receptor kinase activity in clinically unaffected parents of patients suggests that these alterations may be useful genetic markers and more sensitive than insulin binding studies for studying pattern of inheritance of these diseases.

Postreceptor defects in insulin action have been reported in fibroblasts isolated from two patients with Leprechaunism, Leprechaun/Ark-1 and Leprechaun NC-1. We have extended the published reports on glucose, aminoisobutyric acid, and thymidine uptake in these cells to measurements of protein synthesis and protein breakdown. We found a remarkably consistent pattern of responsiveness between the two Leprechaun fibroblast lines. First, protein synthesis proceeded at a low basal rate that was only slightly stimulated by insulin. Second, basal rates of protein breakdown were significantly higher than in normal skin fibroblasts, with approximately equal inhibitory effects produced by 100 nM insulin. Third, the responses of protein synthesis and protein breakdown to insulin required higher concentrations of the hormone to elicit half-maximal effects. Fourth, both Leprechaun cell lines were slow growing in complete medium, a situation that results from low rates of protein synthesis and high rates of protein breakdown. Fifth, the abnormal rates of protein metabolism in the presence of serum were caused not by the inability of serum to produce anabolic responses but because the unstimulated rates reflect a more catabolic basal state. Taken together with previous published results, our measurements suggest a generalized metabolic defect in Leprechaun fibroblasts that can only partly be explained by the reduced sensitivity of the cells to insulin.

A propos de l'observation d'une fille de 8 ans atteinte du syndrome de Donohue, nombre des expressions phenotypiques de ce syndrome sont compatibles avec des taux supraphysiologiques du facteur de croissance epidermique. Cependant, etant donnee la diversite des manifestations phenotypiques, elles peuvent ou non avoir une meme cause et il apparait important de confirmer les presentes donnees sur d'autres cas du syndrome

The syndrome of leprechaunism, characterized by severe intrauterine growth retardation, postnatal growth failure, abnormal facies, and a variety of other abnormalities, was studied in a female infant. The patient, who had hyperglycemia and glycosuria, was found to have markedly elevated serum concentrations of immunoreactive insulin, hyperplasia of the β-cells of the islets of Langerhans, and unresponsiveness to exogenous insulin. Studies were undertaken to determine the mechanism (s) for her insulin resistance and to investigate the relationship between insulin resistance and growth failure. Her circulating insulin appeared to be chemically and biologically normal since it behaved like purified crystalline insulin in RIA and in a placental cell competitive membrane-binding assay for insulin, the elution pattern on gel chromatography was typical of endogenous insulin in serum, the kinetics of its in vitro degradation by insulin glucagon protease were normal, and it exhibited normal biological act...

An infant had the classical features of leprechaunism. Fourteen cases previously published in the literature are reviewed. To our knowledge, this is the first patient with leprechaunism in Israel.

Background/Aims: Donohue and Rabson-Mendenhall syndrome are rare autosomal recessive disorders caused by mutations in the insulin receptor gene, INSR. Phenotypic features include extreme insulin resistance, linear growth retardation, paucity of fat and muscle, and soft tissue overgrowth. The insulin receptor is also expressed in the kidney, where animal data suggest it plays a role in glomerular function and blood pressure (BP) regulation, yet such a role in the human kidney is untested. Patients with biallelic INSR mutations provide a rare opportunity to ascertain its role in man. Methods: Retrospective review of patients with INSR mutations. Data for BP, renal imaging, plasma creatinine and electrolyte levels, as well as urine protein, albumin and calcium excretion were sought from the treating clinicians. Results: From 33 patients with INSR mutations, data were available for 17 patients. Plasma creatinine was low (mean ± SD: 25 ± 9 μmol/l) and mean plasma electrolyte concentrations were within the normal range (n = 13). Systolic BP ranged between the 18th and 91st percentile for age, sex, height and weight (n = 9; mean ± SD: 49 ± 24). Twenty-four-hour urinary calcium data were available from 10 patients and revealed hypercalciuria in all (mean ± SD: 0.32 ± 0.17 mmol/kg/day; normal Conclusions: INSR dysfunction is associated with hypercalciuria and nephrocalcinosis. No other consistent abnormality of renal function was noted. Normotension and stable glomerular function with only moderate proteinuria is in contrast to genetically modified mice who have elevated BP and progressive diabetic nephropathy.

Extreme insulin resistance occurs in patients with primary defects in insulin action at the receptor or postreceptor levels. The condition commonly is associated with acanthosis nigricans and ovarian masculinization. Despite a marked increase in insulin secretion, some patients develop frank diabetes mellitus that does not respond adequately to insulin therapy. Insulinlike growth factor I exerts metabolic effects similar to those of insulin. This study assessed the potential effectiveness of IGF-I as a blood glucose lowering agent in patients with extreme insulin resistance syndromes, including type A insulin resistance, congenital generalized lipodystrophy, and leprechaunism. Among the 11 patients studied, some exhibited mutated insulin receptors, whereas others were suspected to have defects in postreceptor sites. In each patient, plasma glucose levels decreased in response to subcutaneous injections of recombinant human IGF-I (0.1-0.3 mg/kg body wt). The degree of the decrease was roughly comparable with that observed in normal individuals. IGF-I also reduced plasma insulin concentrations. A long-term trial of IGF-I (up to 16 mo) showed that IGF-I (0.1-0.4 mg/kg body wt twice daily) is effective in lowering both fasting and postprandial plasma glucose concentrations with decreases in both fructosamine and HbA1c values. Improvement of acanthosis nigricans was observed in some of the patients. These results suggest that recombinant human IGF-I could be used clinically as a hypoglycemic agent in diabetic patients with extreme insulin resistance in whom insulin treatment is ineffective.

AIMS/HYPOTHESIS: Bi-allelic loss-of-function mutations in the INSR gene (encoding the insulin receptor [INSR]) commonly cause extreme insulin resistance and early mortality. Therapeutic options are limited, but anti-INSR antibodies have been shown to activate two mutant receptors, S323L and F382V. This study evaluates four well-characterised murine anti-INSR monoclonal antibodies recognising distinct epitopes (83-7, 83-14, 18-44, 18-146) as surrogate agonists for potential targeted treatment of severe insulin resistance arising from insulin receptoropathies. METHODS: Ten naturally occurring mutant human INSRs with defects affecting different aspects of receptor function were modelled and assessed for response to insulin and anti-INSR antibodies. A novel 3T3-L1 adipocyte model of insulin receptoropathy was generated, permitting conditional knockdown of endogenous mouse Insr by lentiviral expression of species-specific short hairpin (sh)RNAs with simultaneous expression of human mutant INSR transgenes. RESULTS: All expressed mutant INSR bound to all antibodies tested. Eight mutants showed antibody-induced autophosphorylation, while co-treatment with antibody and insulin increased maximal phosphorylation compared with insulin alone. After knockdown of mouse Insr and expression of mutant INSR in 3T3-L1 adipocytes, two antibodies (83-7 and 83-14) activated signalling via protein kinase B (Akt) preferentially over signalling via extracellular signal-regulated kinase 1/2 (ERK1/2) for seven mutants. These antibodies stimulated glucose uptake via P193L, S323L, F382V and D707A mutant INSRs, with antibody response greater than insulin response for D707A. CONCLUSIONS/INTERPRETATION: Anti-INSR monoclonal antibodies can activate selected naturally occurring mutant human insulin receptors, bringing closer the prospect of novel therapy for severe insulin resistance caused by recessive mutations.

Donohue syndrome is a rare congenital syndrome of insulin-resistance and abnormal glucose homeostasis, caused by mutations in the insulin receptor (INSR) gene. It is characterized by specific phenotypic and clinical features and the diagnosis is based on clinical, biochemical and genetic criteria. We report 2 siblings with Donohue syndrome (cases 1, 2) with multiple clinical and biochemical characteristics. Both patients shared the same mutation and presented with intra-uterine growth restriction, failure to thrive, fasting hyperinsulinaemic hypoglycaemia and episodic post-prandial hyperglycaemia. Less common clinical features were also present, such as atrial septal defect and biventricular hypertrophy, clotting disorders, abnormal liver function tests and nephrocalcinosis. Interestingly, 2 previously unrecognized manifestations of the syndrome were also identified: severe gastrointestinal dysmotility (case 1) and exocrine pancreatic insufficiency (case 2). The co-existence of all the above clinical features makes these cases extremely rare. Gastrointestinal dysmotility should always be considered as a potentially fatal feature in patients with the syndrome, due to the complexity of the possible co-morbidities. In addition, our clinical experience for the first time suggests that pancreatic exocrine insufficiency may offer a possible explanation for the growth retardation observed in some patients with this syndrome. Our finding that replacement treatment with pancreatic enzymes improved weight gain (case 2) implies that all patients with Donohue syndrome should be investigated for exocrine pancreatic insufficiency.