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We report a probable case of abetalipoproteinemia in an infant who presented with unusual symptoms of late-onset vitamin K deficiency. Abetalipoproteinemia is a rare autosomal recessive disease caused by mutation of the microsomal triglyceride transfer protein gene, resulting in the absence of microsomal triglyceride transfer protein function in the small bowel. It is characterized by the absence of plasma apolipoprotein B-containing lipoproteins, fat malabsorption, hypocholesterolemia, retinitis pigmentosa, progressive neuropathy, myopathy, and acanthocytosis. A biopsy of the small intestine characteristically shows marked lipid accumulation in the villi of enterocytes. Large supplements of fat-soluble vitamins A, D, E, and K have been shown to limit neurologic and ocular manifestations. Dietary fat intake is limited to medium-chain triglycerides., Competing Interests: The authors declare no conflict of interest., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Abetalipoproteinaemia (ABL) is an autosomal recessive disorder characterized by very low plasma concentrations of total cholesterol and triglyceride (TG). It results from mutations in the gene encoding microsomal TG transfer protein (MTTP). A nine-month-old girl was admitted to hospital because of fever, cough, diarrhea and failure to thrive. She had low cholesterol and TG levels according to her age. The peripheral blood smear revealed acanthocytosis. Thyroid function test showed central hypothyroidism. Cranial magnetic resonance imaging revealed the retardation of myelination and pituitary gland height was 1.7 mm. A homozygous novel mutation [c.506A>T (p.D169V)] was detected in the MTTP gene. Vitamins A, D, E, and K and levothyroxine were started. The coexistence of ABL and central hypothyroidism has not previously been reported. A homozygous novel mutation [c.506A>T (p.D169V)] was detected in the MTTP gene.

A 16-year-old boy with early-childhood-onset retinal dystrophy and developmental delay was diagnosed with abetalipoproteinemia based on ophthalmic examination, history, and results of a peripheral blood smear. The diagnosis was confirmed by lipid profile and genetic testing, and an older sister was confirmed to be affected as well. Although abetalipoproteinemia is treatable in early childhood, most cases are diagnosed late if at all. We highlight clinical features that should raise suspicion for this treatable but likely under-diagnosed form of early-onset retinal dystrophy and document retinal optical coherence tomography findings for a genetically proven case., (Copyright © 2019 American Association for Pediatric Ophthalmology and Strabismus. Published by Elsevier Inc. All rights reserved.)

"Primary hypobetalipoproteinemia" refers to an eclectic group of inherited lipoprotein disorders characterized by low concentrations of or absence of low-density lipoprotein cholesterol and apolipoprotein B in plasma. Abetalipoproteinemia and homozygous familial hypobetalipoproteinemia, although caused by mutations in different genes, are clinically indistinguishable. A framework for the clinical follow-up and management of these two disorders has been proposed recently, focusing on monitoring of growth in children and preventing complications by providing specialized dietary advice and fat-soluble vitamin therapeutic regimens. Other recent publications on familial combined hypolipidemia suggest that although a reduction of angiopoietin-like 3 activity may improve insulin sensitivity, complete deficiency also reduces serum cholesterol efflux capacity and increases the risk of early vascular atherosclerotic changes, despite low low-density lipoprotein cholesterol levels. Specialist laboratories offer exon-by-exon sequence analysis for the molecular diagnosis of primary hypobetalipoproteinemia. In the future, massively parallel sequencing of panels of genes involved in dyslipidemia may play a greater role in the diagnosis of these conditions.

Background: An acanthocyte is an abnormally shaped erythrocyte. In veterinary medicine, acanthocytes have historically been associated with canine hemangiosarcoma. In human medicine, acanthocytes are rarely observed with neoplastic disease and are more commonly associated with a variety of hereditary and acquired diseases., Objectives: The purpose of the study was to determine what disease processes are associated with the presence of acanthocytes in the peripheral blood of dogs., Methods: Medical records for dogs presented to the Veterinary Teaching Hospital of Colorado State University during January 2004 through June 2008 with acanthocytes documented in their CBCs were retrospectively reviewed., Results: A total of 123 dogs were included, 66 of which were diagnosed with neoplastic disease, most commonly hemangiosarcoma (n = 12), osteosarcoma (n = 11), and lymphoma (n = 11). The remaining 57 dogs had nonneoplastic disease, most commonly observed were gastrointestinal (n = 13), musculoskeletal (n = 8), renal (n = 8), and immune-mediated diseases (n = 7). No statistically significant difference was detected between percent acanthocytes present in dogs with neoplastic and nonneoplastic diseases., Conclusion: Acanthocytosis was observed with a variety of neoplastic and nonneoplastic diseases. While clearly commonly associated, the presence of acanthocytes in a blood smear should not be considered pathognomonic for hemangiosarcoma in dogs., (© 2013 American Society for Veterinary Clinical Pathology.)

Purpose: The purpose of this case study is to raise awareness about an uncommon cause of knee pain., Data Sources: Review of literature was done using PubMed, CINAHL, and Medline. There was no limitation placed on the publication year. Only articles written in English were included., Conclusion: Knee pain is a common diagnosis that many healthcare providers see on a daily basis in their practice. Musculoskeletal injury or trauma is most commonly identified as the cause of this symptom. However, there are rare instances in which an unexpected finding in a client's history and physical exam lead us to an unexpected cause, such as abetalipoproteinemia. Abetalipoproteinemia is a rare autosomal recessive disorder in which an affected individual does not absorb lipids or the lipid-soluble vitamins A, D, E, and K. Multiple body systems are impacted by this fat malabsorption and resultant vitamin deficiencies. Without corrective supplementation, clinical manifestations which are directly related to the vitamin deficiencies will appear as presented in this case study-knee pain., Implications for Practice: This case study emphasizes the need for nurse practitioners to seek out opportunities to further our knowledge which will enhance our clinical expertise as well as the quality of the health care we provide to our clients., (©2012 The Author ©2012 American Association of Nurse Practitioners.)

Background: Abetalipoproteinemia (ABL; OMIM 200100) is a rare monogenic disorder of lipid metabolism characterized by reduced plasma levels of total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and almost complete absence of apolipoprotein B (apoB). ABL results from genetic deficiency in microsomal triglyceride transfer protein (MTP; OMIM 157147). In the present study we investigated two unrelated Tunisian patients, born from consanguineous marriages, with severe deficiency of plasma low-density lipoprotein (LDL) and apo B., Methods: Intestinal biopsies were performed and The MTTP gene was amplified by Polymerase chain reaction then directly sequenced in patients presenting chronic diarrhea and retarded growth., Results: First proband was homozygous for a novel nucleotide deletion (c. 2611delC) involving the exon 18 of MTTP gene predicted to cause a non functional protein of 898 amino acids (p.H871I fsX29). Second proband was homozygous for a nonsense mutation in exon 8 (c.923 G > A) predicted to cause a truncated protein of 307 amino acids (p.W308X), previously reported in ABL patients., Conclusions: We discovered a novel mutation in MTTP gene and we confirmed the diagnosis of abetalipoproteinemia in new Tunisian families., Virtual Slides: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8134027928652779.

Huntington's disease and neuroacanthocytosis may present similar clinical and MRI features. It is important to differentiate these findings since treatment and prognosis vary vastly between them. The aim of this article is to familiarize radiologists with the differentiating features of Huntington's disease and various diseases comprising neuroacanthocytosis. A 40-year-old Indian man with extrapyramidal symptoms was referred for MRI. The clinical diagnosis was Huntington's disease, but there were a few atypical clinical features such as a history of biting the tongue, tics, marked hyporeflexia and lower limb muscle wasting. MR showed atrophy of the caudate nucleus and putamen with iron deposition in the basal ganglia, which can be seen in Huntington's disease and in neuroacanthocytosis. An increased blood acanthocyte level was subsequently confirmed. Further work-up revealed increased serum creatine phosphokinase levels, normal serum lipoprotein levels and depressed K cell antigen activity on serological studies, confirming the diagnosis of McLeod syndrome. McLeod syndrome is one of the distinct phenotypes of neuroacanthocytosis. Neuroacanthocytosis is a group of disorders with increased serum acanthocyte counts and neurological involvement. Various causes of neuroacanthocytosis are discussed. It is important to consider the possibility of neuroacanthocytosis when features typical of Huntington's disease are encountered on imaging.

Introduction: Abetalipoproteinemia is a rare inherited disorder characterized by very low plasma levels of cholesterol and triglycerides, secondary to a dramatic decrease in apolipoprotein B-containing lipoproteins, which is induced by a mutation in the microsomal triglyceride transfer protein gene., Case: In our paper, we describe an atypical clinical manifestation of this condition in a young man, which included the presence of hypogonadism and chronic adrenal failure. We connect the development of both endocrine disorders with very low plasma levels of cholesterol, which is uptaken by the gonads and adrenal cortex and used as a substrate for steroidogenesis, accentuated by carbamazepine treatment. Testosterone treatment and administration of hydrocortisone, fludrocortisone and dehydroepiandrosterone resulted in a significant improvement in a patient's condition., Conclusions: This case shows that untreated or inaccurately managed long-lasting abetalipoproteinemia may impair the production of steroid hormones and lead to the development of some endocrine disorders.

Inherited cerebellar ataxias constitute a complicated and heterogeneous group of neurodegenerative disorders affecting the cerebellum and/or spinocerebellar tract, spinal cord and peripheral nerves. A peripheral neuropathy is frequently seen in inherited cerebellar ataxias although it rarely reveals the disease. Moreover, the peripheral neuropathy is helpful for the diagnostic procedure and contributes to the functional prognosis of the disease. Thus, electroneuromyography is essential in the algorithm for the diagnosis of inherited cerebellar ataxias, as well as brain MRI (looking especially for cerebellar atrophy) and the assessment of several biomarkers (alpha-foetoprotein, vitamin E, albumin, LDL cholesterol, lactic acid, phytanic acid)., (Copyright © 2010 Elsevier Masson SAS. All rights reserved.)

Abetalipoproteinemia (ABL) is characterized by acanthocytosis, hypocholesterolemia, and steatorrhea. Here, we describe a case of ABL associated with rickets and dysmorphic findings and the subsequent therapeutic course in an 18-month-old male referred for evaluation for failure to thrive and chronic fatty diarrhea. Examination revealed a pale child, dysmorphic face, and signs of rickets. Laboratory examination revealed low hemoglobin (3.7 gm/dl), low albumin (28 gm/L), low cholesterol and triglyceride levels. The blood smear showed acanthocytes while the small bowel histology showed the enterocytes were distended with lipid droplets. He was diagnosed with ABL and treated with fat-soluble vitamins (ADEK), and hydrolyzed protein formula containing medium chain triglycerides. Three months later, his fatty diarrhea becomes normal stool, his serum fat-soluble vitamins normalized, and his weight increased from 4.1 kg to 5.9 kg.

Background: Abetalipoproteinemia is a rare, autosomal recessive disease, in which the absence of beta-lipoprotein results in the malabsorption of fat-soluble vitamins. There are few reported complications from abetalipoproteinemia during pregnancy. We present a case of untreated abetalipoproteinemia complicating the puerperium., Case: A 23-year-old, gravida 3, para 0020 woman presented to an outside facility in labor, and her delivery was complicated by postpartum hemorrhage and a large vulvar hematoma. She was coagulopathic and transferred for suspected disseminated intravascular coagulation. Her preexisting medical history was not appreciated by the transferring facility., Conclusion: Abetalipoproteinemia in pregnancy is rare. Untreated disease conveys multi-system organ dysfunction and has ramifications in labor and delivery. Clinicians must elicit a comprehensive medical history to properly manage complications in the puerperium.

Abetalipoproteinaemia (ABL), an extremely rare recessive disorder, is characterized by exceptionally low or undetectable concentrations of apolipoprotein (apo) B-containing lipoproteins. ABL results from mutations in the gene encoding microsomal triglyceride transfer protein (MTP), a chaperone that facilitates the transfer of lipids onto apoB. Patients with ABL often present in childhood with a range of symptoms including fat malabsorption and manifestations of fat-soluble vitamin deficiencies. We describe a patient with sub-clinical hypothyroidism and ABL found to be compound heterozygous for a novel splice site mutation of intron 1 (c.61 + 2T > C) and a single adenine insertion in MTP exon 4 (c.419-420insA) that results in a frameshift and a protein truncated at 140 amino acids.

We report a 53-year-old woman with probable Bassen-Kornzweig syndrome. Her parents were a consanguineous marriage. At two years of age, she developed night blindness. During her childhood she had severe diarrhea that disappeared in adulthood. At 26 years of age, she was diagnosed as having retinitis pigmentosa and her visual acuity became worse thereafter. She noted tremor in the right hand at 37 years of age, gait ataxia at 42, and developed tremor in the bilateral lower extremities at 48. On admission, bilateral visual disturbance, resting and postural tremor, moderately poor coordination, mild distal dominant sensory impairment, an absence of tendon reflex in all four extremities, moderate to severe gait ataxia, and positive Romberg sign were found. Muscle rigidity and akinesia were not observed. Intelligence and muscle power were normal and pathological reflexes were absent. Acanthocytes were found in blood. Serum chemistry showed remarkable decreases in total cholesterol (54 mg/dl, normal 180-220), triglyceride (0 mg/dl, normal 30-150), beta-lipoprotein (3 mg/dl, normal 190-500), apoA-1 protein (66 mg/dl, normal 105-184), apoA-2 protein (11 mg/dl, normal 26-46), apoB protein (0 mg/dl, normal 38-104), apoC-2 protein (1.1 mg/dl, normal 1.2-6.4), vitamin A (297 ng/ml, normal 431-1,041), and vitamin E (0.19 ng/dl, normal 0.75-1.41). While, a marked increase in PIVKA II (703 mAU/ml, normal<40) due to a decrease in vitamin K was found. She was thus diagnosed as having Bassen-Kornzweig syndrome or hypo-betalipoproteinemia. Although brain MRI was normal, single-photon emission CT (SPECT) showed mildly decreased perfusion in the left parietal cortex and right striatum. Motor nerve conduction velocities were normal, but sensory nerve action potentials were not evoked in all four extremities. Surface EMG recorded on the right radial extensor and flexor carpi muscles at rest showed a 4.5 Hz tremor. Vitamin replacement therapy with vitamin A (10,000 IU/day), E (200 mg/day), and K (10 mg/day) was initiated. Several days after treatment, amplitude of resting tremor ameliorated mildly. Clonazepam was administered (0.5 mg/day) for further treatment. After one-month of treatment, vitamin A (656 ng/ml) and E (0.39 mg/dl) levels were elevated and PIVKA II level (29 mAU/ml) decreased. Only a mild right hand tremor remained, but sensory impairment and gait ataxia were not changed. The cause of Bassen-Kornzweig syndrome is a deletion of the microsomal triglyceride transfer protein (MTP) gene. While, familial hypo-betalipoproteinemia, due to a mutation of apolipoprotein B gene, is known to show the same phenotype. Because of the patient's refusal of genetic examination, which disease she has cannot be conclusively determined. Intention tremor was reported in Bassen-Kornzweig syndrome. However, her 4.5 Hz tremor was also present at rest, which resembled resting tremor in Parkinson's disease. Pathophysiology of Bassen-Kornzweig syndrome is known to be due to hypo-vitaminosis. Decreased [18F]-dopa uptake in striatum of patients with long-term hypo-vitamin E has been reported in PET study. Mild hypoperfusion was found in the striatum of the present cases: indicating that her tremor was associated with striatonigral damage. Thus, careful observation of extrapyramidal signs is necessary in abeta- or hypo-betalipoproteinemia.

Background: Abetalipoproteinemia (ABL) is a metabolic disorder resulting in poor absorption of fat-soluble vitamins., Case: Two pregnancies in a woman with ABL are reported, contrasting outcomes with subtherapeutic and normal vitamin levels., Conclusion: Fat-soluble vitamin levels in pregnancy are critical for many aspects of fetal development. This report details a congenital ophthalmologic finding that may be associated with vitamin A deficiency.

Abetalipoproteinemia (ABL) is a rare autosomal recessive disorder that is characterized by defective assembly and secretion of plasma apolipoprotein (apo) B-containing lipoproteins. This disorder results from mutations in the MTP gene encoding the microsomal triglyceride transfer protein. We report a 58-year-old male homozygote for a missense mutation, S590I, in MTP. The patient had a lifelong history of fat malabsorption, but was only diagnosed with ABL at age 52, based upon such classic features as absence of apo B-containing lipoproteins, acanthocytosis, atypical retinitis pigmentosa and markedly depressed serum beta-carotene concentration. However, his presentation was notable not only by survival to the sixth decade of life without specific treatment, but also by the absence of neurological involvement and by normal serum vitamin E concentration. He subsequently developed adenocarcinoma of the ileum, which required ileal resection. Therefore, this missense mutation appears to be associated with a late-presenting and relatively mild ABL phenotype that lacks some classical features, particularly neuropathy, but appears to be associated with other atypical features, specifically small intestinal cancer.

Both defective LDL receptors (familial hypercholesterolaemia, FH) and mutations in apolipoprotein B (apoB) on LDL (familial defective apoB, FDB) give rise to a phenotype of elevated LDL cholesterol. We sought to compare the metabolic basis of the two conditions by examining apoB turnover in FDB and FH subjects. A group comprising three heterozygous and one homozygous FDB subjects were compared with five FH heterozygotes and 17 control subjects using a deuterated leucine tracer. Kinetic parameters were derived by multicompartmental modelling. FH heterozygotes had a reduced delipidation rate for VLDL, which led to a moderate increase in plasma triglyceride. Compared with controls and FH, the FDB subjects converted 44% less IDL to LDL. The LDL FCR was reduced to a similar extent in FDB and FH. In all subjects LDL plasma levels appeared to be regulated by the LDL FCR and the rate of production of small VLDL. We conclude that disturbances in IDL metabolism provide the basis for understanding why FDB is less severe than FH. Our findings suggest that an apoB-LDL receptor interaction is important in the IDL to LDL conversion.

In this chapter; we have described the role of nutritional supplements or selective dietary restriction (or both) on the maintenance and function of the retina and nervous system in some diseases. Oral vitamin A therapy has proven to be effective in the treatment of the common forms of retinitis pigmentosa. Bassen-Kornzweig disease can be treated with vitamin A and vitamin E and, in some cases, with vitamin K. Vitamin E therapy for Friedreich-like ataxia associated with retinitis pigmentosa has been shown to be effective in the short term. Classic Refsum's disease responds to a low phytol-low phytanic acid diet. Undoubtedly, future research will bring more insight into the biochemical pathways responsible for other diseases and, it is hoped, aid in developing treatments for additional retinal degenerations associated with systemic neurological disease.

Purpose: To assess the long-term efficacy of combined vitamin A and E treatment in preventing retinal degeneration in patients with abetalipoproteinaemia (ABL) or homozygous hypobetalipoproteinaemia (HBL)., Methods: Ten patients with ABL and 3 with homozygous HBL who were treated with oral supplements of vitamins A and E were studied. Systemic, ophthalmological and electroretinographic follow-up for a mean of 11.7 years (range 4-20 years) after onset of treatment was evaluated., Results: Despite vitamin A and E treatment, 7 of 10 patients who began treatment prior to 2 years of age and all 3 patients who began treatment later in life manifested unusual fundoscopic pigmentary changes over time. At the end of follow-up, 11 of 13 patients had subnormal mixed cone-rod electroretinogram amplitudes. Seven of 10 patients for whom perimetry was available had mild to severe constriction of the visual fields., Conclusions: Combined oral vitamin A and E supplementation that is initiated prior to 2 years of age can markedly attenuate the severe retinal degeneration that is associated with untreated ABL or homozygous HBL. Yet, fundoscopic and functional retinal changes do occur despite early initiation of vitamin treatment. Therefore, the adequacy of the present treatment protocol for ABL and homozygous HBL should be re-evaluated.

Abetalipoproteinemia is a rare autosomal recessive disorder characterized by steatorrhea, poor weight gain, acanthocytosis and retinitis pigmentosa. Here we peresent a six-month-old patient with abetaliporoteinemia. He had a history of chronic diarrhea from the first month of life. He was cachectic and his motor development was delayed. Microscopic examination of the stool revealed fat. Mild anemia with reticulocytosis, acanthocytosis, low triglyceride, low cholesterol, low-density lipoprotein, high-density lipoprotein, and apolipoprotein A and B were detected. Ophthalmological examination was normal. Peroral jejunal capsule biopsy revealed normal villi and significant lipid deposition in the cytoplasm of affected cells. The patient was given large doses of vitamins E and A.

Objective: Description of rickets as an unexpected initial manifestation in two children with abetalipoproteinemia and hypobetalipoproteinemia, and elucidation of its pathophysiology in these conditions., Methodology: Two infants aged two and six months with abetalipoproteinemia and hypobetalipoproteinemia respectively had clinical rickets at presentation, confirmed radiologically and biochemically. Vitamin D intake and serum levels were measured and other causes of rickets were looked for., Results: Vitamin D intake and laboratory studies levels were suggestive of rickets due to calcium deficiency instead of vitamin D deficiency. Healing of rickets occurred with dietary treatment of the malabsorption, without any dietary calcium or significant vitamin D supplementation., Conclusion: Steatorrhea-induced calcium malabsorption seems to be the most likely cause of rickets in this entity.

A 16-year-old girl is described with abetalipoproteinaemia who underwent liver transplantation for hepatic cirrhosis. After this procedure her serum lipoprotein profile was corrected; however, fat malabsorption and steatorrhea persisted because the primary defect, a mutant microsomal triglyceride-transfer protein, remains expressed in the intestine.

Abetalipoproteinemia (ABL) and homozygous hypobetalipoproteinemia (HBL) are inherited disorders which are classically characterized by progressive retinal and spinocerebellar disease, fat-soluble vitamin deficiency, and absence of apolipoprotein (apo) B from the plasma. Using immunoaffinity chromatography with an anti-apo B antiserum, we isolated apo B-containing lipoprotein (LpB) particles from the plasma of 4 ABL and 2 HBL patients. The LpB particles were characterized and compared with low density lipoprotein (LDL) and LpB isolated from normal plasma. The ABL/HBL LpB particles were similar in size and charge to normal LpB particles but were relatively enriched in several other apolipoproteins. They contained alpha-tocopherol in a ratio to cholesterol that was proportionately much higher than the very low ratio of alpha-tocopherol to cholesterol in plasma. They bound saturably to fibroblasts and were internalized and degraded similarly to LDL. Hence, the molecular defects in ABL and HBL permit the secretion of a very small number of apo B-containing lipoproteins which may be important for transport of alpha-tocopherol to peripheral tissues.

Angioid streaks were observed in two patients with abetalipoproteinemia. The progression of the angioid streaks was minimal over the years that these patients received vitamin A and E supplementation, though in one patient the development of subretinal neovascular membranes within the angioid streaks was the cause of rapid central visual loss. The simultaneous appearance of two rare entities in unrelated individuals strengthens the relationship between these two disorders that has been suggested by previous case studies. The authors propose a common metabolic pathway involving trace element deficiencies that may account for this relationship as well as the association of angioid streaks with other rare disorders such as Paget's disease, hypoparathyroidism, lead poisoning, hyperphosphatemia, and a number of hemoglobinopathies. Their study of these two patients underscores the need for further investigations as to the role of copper, zinc and omega-3 fatty acids in the pathogenesis of retinopathy in abetalipoproteinemia.

Dyskinesias as the neurologic complications of hematologic disorders were described in detail on abetalipoproteinemia and ataxia telangiectasia as well as in summary on other hematologic diseases. Dyskinesias as the iatrogenic neurologic manifestations in hematologic disorders were also briefly described. Although the pathogenetic mechanisms of dyskinesias observed in hematologic disorders were quite heterogeneous, they could provide us with good suggestions and clues to clarify the true mechanisms of their own as well as other dyskinesias.

Abetalipoproteinaemia (ABLP) was diagnosed in a brother and sister, 9 and 13 years old, presenting with symptoms of malabsorption during the neonatal period. Both children showed most of the main clinical features of ABLP, including neurological, and ophthalmic symptoms, and mental retardation. Acanthocytosis of erythrocytes was almost complete in the affected children, while in most of the remaining 11 members of their three-generation family, it was found in less than 50% of red blood cells. Absence of apoprotein B and low concentrations of apo A-I and lipids were found only in ABLP-affected children. Among five siblings only the two affected children had ABLP-characteristic lipid storage in enterocytes. The latter features correlated better with clinical symptoms than did the acanthocytosis of erythrocytes.

The article defines apolipoprotein diseases as the structural defects of apolipoproteins or disorders in their synthesis or secretion. The survey covers a range of atherogenous defects, providing a detailed description of their clinical-biochemical and genetic aspects as well as diagnostic and differential diagnostic criteria. Attention is paid also to the significance of analytical isoelectric focusing.

The retinal and neurological complications of abetalipoproteinaemia may be preventable by replacing vitamins A and E from an early age, but their role in adult presentations is less clear. Two adult females with abetalipoproteinaemia have received 8 and 10 years respectively of replacement therapy with vitamins A, E and linoleic acid. In Case 1, visual function improved objectively on commencing therapy but has subsequently deteriorated and her neuropathy has slowly progressed. The rate of progression of neurological impairment in Case 2 was slowed but not halted by therapy, and her severe visual disturbance was unaffected. Replacement by fat soluble vitamins has only a limited role in the management of abetalipoproteinaemia once irreversible neurological/retinal damage has occurred.

Evidence has accumulated that vitamin E is essential for normal neurological function. It is a fat-soluble vitamin, and, therefore, deficiency states are most likely to occur in patients with fat malabsorption. If such patients have low serum vitamin E concentrations, it is important to initiate appropriate vitamin E therapy with the aim of restoring and maintaining normal serum vitamin E concentrations and preventing long-term neurological disability. This is likely to become a more frequent problem with the increasing survival of patients with chronic fat malabsorptive states. As a corollary, it would also seem reasonable to measure serum vitamin E concentrations in all patients with spinocerebellar disorders, whatever the supposed cause.

A characteristic pattern of acquired exotropia, progressive paresis of the medial rectus muscles, and dissociated nystagmus on lateral gaze was found in three patients with abetalipoproteinemia. Study with electronystagmography of the eye movements of one patient revealed abnormally slow voluntary saccades and slow or absent fast components of vestibular nystagmus, optokinetic nystagmus, and jerk-type, disassociated nystagmus. Defects in central nervous system centers generating saccadic eye movements are postulated.