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Congenital lipodystrophies are heterogeneous genetic diseases, leading to the loss of adipose tissue. This loss of adipose tissue can be generalized or partial, thus defining different phenotypes. These lipodystrophies have a major metabolic impact, secondary to lipotoxicity. This lipotoxicity is responsible for insulin resistance, dyslipidemia and hepatic steatosis. The severity of the metabolic impact correlates with the severity of the loss of adipose tissue. Mutations in 15 predisposition genes are currently described; BSCL2 and AGPT2 genes are the major genes in the generalized forms. On the contrary, LMNA and PPARG gene mutations are recovered in partial lipodystrophies forms. These different genes encode for proteins involved in adipocyte physiology, altering adipocyte differentiation, triglycerides synthesis and lysis or playing a major role in the lipid droplet formation. Congenital lipodystrophies treatment is based on the management of metabolic comorbidities but recombinant leptin therapy appears to have promising results. These different points have been recently discussed during the 2015 Endocrine Society Congress, notably by S. O'Rahilly and are highlighted in this review., (Copyright © 2015 Elsevier Masson SAS. All rights reserved.)

Lamins A and C, encoded by the LMNA gene, are nuclear proteins expressed in all post-mitotic cells. Together with B-type lamins, they form a meshwork of proteins beneath the inner nuclear membrane, the lamina, in connection with the cytoskeleton. Lamins A/C also interact with chromatin and numerous proteins, including transcription factors. Mutations in LMNA are responsible for more than ten different disorders, commonly called "laminopathies". These diseases affect tissues in a specific (striated muscle, adipose tissue, peripheral nerve) or in a systemic manner (premature ageing syndromes). This wide spectrum of phenotypes is associated to a wide variety of mutations. This large clinical and genetic heterogeneity, unique to the LMNA gene, makes genotype-phenotype relations particularly difficult to establish. However, correlations have been obtained in several cases. Hence, LMNA mutations identified in premature ageing syndromes lead to the accumulation of immature proteins with a toxic effect for cells. Mutations in laminopathies of the adipose tissue mainly localize in the Ig-like domain of the proteins, potentially affecting the interaction with the SREBP-1 transcription factor. In laminopathies of the striated muscles, the mutations are spread throughout the gene. These mutations are thought to induce structural modifications of the proteins, thereby affecting their polymerization into nuclear lamina. Such defect would lead to a mechanical weakness of the nuclear lamina and of the cells, particularly in striated muscles continuously stretching. The exploration of pathophysiological mechanisms of LMNA mutations largely benefits from the numerous mouse models created, which have been widely used to analyze affected molecular pathways and to test putative therapeutic treatments., (Société de Biologie, 2011.)

Primary lipodystrophies represent a heterogeneous group of very rare diseases with a prevalence of less than 1 case for 100.000, inherited or acquired, caracterized by a loss of body fat either generalized or localized (lipoatrophy). In some forms, lipoatrophy is associated with a selective hypertrophy of other fat depots. Clinical signs of insulin resistance are often present: acanthosis nigricans, signs of hyperandrogenism. All lipodystrophies are associated with dysmetabolic alterations with insulin resistance, altered glucose tolerance or diabetes and hypertriglyceridemia leading to a risk of acute pancreatitis. Chronic complications are those resulting from diabetes involving the retina, kidney and nerves, cardiovascular complications and steatotic liver lesions that could result in cirrhosis. Genetic forms of generalized lipodystrophy (or Berardinelli-Seip syndrome) result, in most cases, from recessive mutations in one of two genes: either BSCL2 coding seipin or BSCL1 coding AGPAT2, an acyl-transferase involved in triglyceride synthesis. Acquired generalized lipodystrophy (Lawrence syndrome) is of unknown origin but is sometimes associated with signs of autoimmunity. Partial lipodystrophies can be familial with dominant transmission. Heterozygous mutations have been identified in the LMNA gene encoding nuclear lamin A/C belonging to the nuclear lamina, or in PPARG encoding the adipogenic transcription factor PPARgamma. Some less typical lipodystrophies, associated with signs of premature aging, have been linked to mutations in LMNA or in the ZMPSTE24 gene encoding the protease responsible for the maturation of prelamin A into lamin A. Acquired partial lipodystrophy (Barraquer-Simons syndrome) is characterized by cephalothoracic fat loss. Its aetiology is unknown but mutations in LMNB2, encoding the lamina protein lamin B2, could represent susceptibility factors. Highly active antiretroviral treatments for HIV infection are currently the most frequent cause of acquired secondary lipodystrophic syndromes. The genetic diagnosis is performed in specialized laboratories and, in the most severe forms, antenatal diagnosis could be proposed. Treatment of diabetes, dyslipidemia and complications involves the classical intervention strategies. Insulino-sensitizing drugs are useful. Therapeutic trials with recombinant human leptin in patients with very low leptin levels reported good results with respect to the metabolic and liver alterations. The prognosis is linked to the precocity and severity of the diabetic, cardiovascular and liver complications.

Lipodystrophic syndromes regroup a heterogeneous group of genetic or acquired diseases. Lipodystrophy, an altered development and/or repartition of body fat, is associated with alterations of lipid and glucose metabolism with insulin resistance. Genetic forms, rare, can be generalized and recessive resulting from mutations in the seipin or AGPAT2 gene. Partial lipodystrophies are dominant and observed in patients mutated in the gene encoding PPAR-gamma or lamin A/C, a gene seen also mutated in patients with syndromes of premature aging. Acquired forms are common and regroup the highly prevalent Metabolic Syndrome, hypercorticism together with lipodystrophy related to antiretroviral treatment of HIV-infected patients.

Laminopathies are a group of diseases due to mutations of type A-lamins, a group of proteins lining the inner aspect of cell nuclei. These diseases illustrate the complexity of the genotype-phenotype relationship characteristic of same genetic diseases. Since the discovery of the causal role of LMNA gene mutations in the genesis of Emery Dreifuss muscular dystrophy in 1999, no less than eight other diseases have been associated with mutations of this same gene! The tissue-specific nature of the clinical manifestations, contrasting with the ubiquitous expression of these proteins, has incited much research concerning the physiological role of lamins, considered to be much broader than the structural function initially put forward. Certain laminopathies, which combine insulin resistance, android distribution of adipose tissue, dyslipidemia, early atherosclerosis, and hepatic steatosis, appear very similar though more severe to the frequent dysmetabolism syndrome. The relationships of laminopathies with accelerated aging syndrome, Hutchinson-Gilford progeria, or progeroid syndromes, which are also related to A/C lamin anomalies, could provide new avenues of research on the pathogenesis of the metabolic syndrome. In addition, clinicians have to be aware of atypical and milder forms of laminopathies, that require specific investigations and molecular screening of relatives allowing an adequate medical management.

The Seip Berardinelli or undiagnosed endocrine metabolic syndrome is a rare autosomal recessive pathology mainly described in families of Portuguese origins. This syndrome presents various metabolic disturbances responsible of various dysmorphies. We report the case of two brothers seen during their childhood for respiratory, speaking and feeding problems related to a class 3 of Angle and macroglossia. The object was to study the interaction between the size of the tongue, the prognathism and the disturbances presented in order to organize early surgery (partial glossectomy).

Membranous lipodystrophy is a rare disease in which cyst-like lesions of fat occur in subcutaneous and other sites including bone marrow, together with sudanophilic leukoencephalopathy. The disease has been reported mostly in Finland and in Japan, with sporadic cases from USA, Belgium, Italy, and France. The cyst-like lesions of limb bones progress in early adult life, usually followed by neurological disorders including convulsions and presenile dementia. Histologically, the fat cells of the bone marrow, synovial membrane, and other sites, are replaced by a convoluted, hyaline, eosinophilic membrane that surrounds a large space. The histochemical and ultrastructural characteristics of the membranes are described. In the brain, atrophy of the subcortical white matter of the frontal and temporal lobes with marked astrocytosis and fibrillary gliosis, and a slight or moderate degeneration of myelin sheaths, are the most prominent changes. Genetic studies of the disease have been reported, revealing an autosomal recessive gene, explaining both its sporadic and familial occurrence, with mutations involving the gene encoding a transmembrane protein, key activating signal transduction element in NK cells (TYROBP). The pathogenesis of membranocystic changes is still unknown: result of a metabolic disorder or circulatory disturbances.

The authors discuss the nosological position and the aetiology of a complex of malformations affecting a boy, born at the end of a 40-week pregnancy with a weight of 1420 g and height of 42.5 cm, who died at the age of 3 1/2 months. The case presented an association of an acrocephalosyndactyly, phalangeal hypoplasias with anonychia, aplasia of the abdominal muscles, a genital hypoplasia with cryptorchidism and hypospadias, patches of lipodystrophy localised on the outside of the arms, at the folds of the elbow and the popliteal fossae. The autopsy revealed a large interventricular communication, absence of common mesentery and especially important cerebral anomalies (smooth brain, absence of interhemispherical suture, disorganization of the basal ganglia). The genetic study suggested a spontaneous abortion 2 1/2 months before the birth of the patient and revealed, in the mother, the presence of bilateral clinodactylies of the fingers and a unilateral syndactyly of the big toes.