Lipodystrophy, Congenital Generalized, Type 1

A number sign (#) is used with this entry because congenital generalized lipodystrophy type 1 (CGL1) is caused by homozygous or compound heterozygous mutation in the gene encoding 1-acylglycerol-3-phosphate O-acyltransferase-2 (AGPAT2; 603100) on chromosome 9q34.

Description

Congenital generalized lipodystrophy (CGL), or Berardinelli-Seip syndrome, is a rare autosomal recessive disease characterized by a near absence of adipose tissue from birth or early infancy and severe insulin resistance. Other clinical and biologic features include acanthosis nigricans, muscular hypertrophy, hepatomegaly, altered glucose tolerance or diabetes mellitus, and hypertriglyceridemia (Garg, 2004).

Genetic Heterogeneity of Congenital Generalized Lipodystrophy

Congenital generalized lipodystrophy type 2 (269700) is caused by mutation in the BSCL2 gene (606158). Congenital generalized lipodystrophy type 3 (612526) is caused by mutation in the CAV1 gene (601047). Congenital generalized lipodystrophy type 4 (613327) is caused by mutation in the PTRF gene (603198).

Clinical Features

Congenital generalized lipodystrophy was originally described by Berardinelli (1954) and Seip (1959) as a disorder of metabolism, lipodystrophy, and endocrine abnormalities. Seip (1959) reported affected brother and sister, and suggested diencephalic origin. Lipodystrophic muscular hypertrophy (Senior, 1961) may be the same entity. Reed et al. (1965) reported congenital lipodystrophy with diabetes and acanthosis nigricans. Seip (1971) reviewed published cases.

Hamwi et al. (1966) discussed lipoatrophic diabetes and noted that substances with insulin-antagonizing and fat-mobilizing properties have been found in the urine of affected patients. Mabry and Hollingsworth (1971) presented evidence for abnormal pituitary function with secretion of an abnormal hormone with melanotrophic and growth hormone properties. In 1 case, surgical hypophysectomy was followed by marked improvement. In postmortem examination of a case, Berge et al. (1976) found hypothalamic lesions judged to be of a malformative or hamartomatous nature. The authors pointed out that the Russell emaciation syndrome (Russell, 1951), which does not appear to be mendelian, had been shown to be due to a hypothalamic lesion, usually glioma, and that cerebral gigantism may likewise be of diencephalic origin.

Brunzell et al. (1968) noted that 2 affected sibs had been reported in each of 5 families, and in 4 other families the parents were consanguineous, suggesting autosomal recessive inheritance. Brunzell et al. (1968) reported a family in which 5 of 12 sibs had a combination of congenital generalized lipodystrophy and cystic angiomatosis with progressive incapacitating bone involvement (termed by some as 'Brunzell syndrome'). Two had subcutaneous soft tissue angiomas. The lipodystrophy was accompanied by acanthosis nigricans, large hands and feet, acromegaloid facial features, lipemia, and hepatosplenomegaly, typical of Berardinelli-Seip congenital lipodystrophy.

Huseman et al. (1978) reported 3 black sibs with congenital lipodystrophy with a severe disturbance in carbohydrate metabolism manifested by increased plasma levels of glucagon and insulin and resistance to exogenous insulin. Huseman et al. (1979) reported 3 sisters with congenital generalized lipodystrophy and cystic angiomatosis of the long bones. One girl had polycystic ovarian disease. Huseman et al. (1979) noted that labial hypertrophy, sexual precocity, and oligomenorrhea had also been described in this disorder (Brunzell et al., 1968). Dorasamy (1980) reported a case of an affected female infant with first-cousin parents.

Van Maldergem et al. (1992) reported a girl, born of an uncle-niece mating, with features characteristic of total lipodystrophy, including absent subcutaneous fat, hyperlipidemia, acanthosis nigricans, facial dysmorphia, and mild mental retardation with an IQ of 50. At the age of 13 years, the girl was found to have large multilocular cysts at the ends of the long bones, particularly the humeri and femora. At the age of 17 years, oligospaniomenorrhea (few and scanty menses) was a complaint, and polycystic ovaries were demonstrated. Insulin resistance was progressive. Van Maldergem et al. (1992) considered Brunzell syndrome, which they suggested includes cystic angiomatosis, to be distinct from Berardinelli-Seip syndrome.

Seip and Trygstad (1996) presented information on several patients with congenital generalized lipodystrophy followed for almost 40 years. They also described a patient with acquired generalized lipodystrophy, a disorder that was first reported by Ziegler (1928) and later by Lawrence (1946), which may represent an autoimmune disorder. In congenital lipodystrophy, insulin resistance is present from birth, resulting in hyperinsulinemia, dyslipidemia, and insulin-resistant diabetes with an anabolic syndrome worsened by a voracious appetite. Growth velocity is increased in preschool age children, and organomegaly is observed with hypertrophic cardiomyopathy that can be lethal in early adulthood. Three patients of Seip and Trygstad (1996) died at the ages of 24, 32, and 37 years. Another, alive at age 39 years, suffered from stenocardia (angina pectoris). Their first patient was born in 1952 of second-cousin parents. She had a healthy twin brother and an affected younger brother. She suffered from severe hyperhidrosis with moist and warm hands, attributable to an increased energy metabolism. Insulin-resistant diabetes (IDDM; 222100) developed at age 12 years and diabetic nephropathy and neuropathy (see 603933) were evident by age 16 years. She died at age 32. The affected brother was 192 cm tall at the age of 17 years. He was married with 3 healthy children. Bjornstad et al. (1996) reported that all patients of Seip and Trygstad (1996) had hypertrophic hearts, mostly with deranged diastolic, but also systolic, function. One had pulmonary hypertension. Conspicuous acanthosis nigricans was illustrated in 2 patients aged 8 and 9 years. One of the patients from a Finnish-derived population of Norway was described as 'not as athletic as the other patients,' and pneumoencephalography showed more extensive changes than in the other patients, with dilatation of both lateral ventricles, the third ventricle, and the basal cisterns. He was somewhat more mentally retarded. He died of heart failure at the age of 35 years.

Uzun et al. (1997) described 3 patients with multiple peripheral pulmonary artery stenoses in association with congenital generalized lipodystrophy. Two were a brother and sister, aged 2 and 6 years, respectively; the third was a 14-year-old girl.

Van Maldergem et al. (2002) studied 70 affected individuals from 44 unrelated families with congenital generalized lipodystrophy. Forty-five patients from 24 families had BSCL2 (269700) and 21 patients from 17 families had BSCL1. Two European families had no BSCL2 mutations and did not show linkage to chromosome 9q34, indicating the existence of an additional locus, which the authors termed BSCLX. All subjects of African ancestry (35%) were in the BSCL1 group. Congenital onset of lipoatrophy occurred in 79.5% of patients with BSCL2 compared to 61% of other cases. Onset of diabetes was the same in all patients. All patients had skeletal muscle hypertrophy, and the prevalence of hypertrophic cardiomyopathy was approximately 20% in all groups. Seven of 45 (15%) BSCL2 patients died prematurely (range, 4 months to 35 years of age), compared to no premature deaths in patients with BSCL1. The most significant finding was an increased frequency of mild or moderate intellectual impairment in the BSCL2 group (78%) compared to BSCL1 (10%), yielding an odds ratio of 23.5. There was no correlation between site and type of seipin mutation and intellectual impairment. Van Maldergem et al. (2002) concluded that BSCL1 is a milder disease than BSCL2.

Simha and Garg (2003) compared whole-body adipose tissue distribution by magnetic resonance imaging (MRI) in 10 congenital generalized lipodystrophy patients, of whom 7 (6 females, 1 male) had CGL1 and 3 (2 males, 1 female) had CGL2 (269700). Both subtypes had marked lack of metabolically active adipose tissue located at most subcutaneous, intermuscular, bone marrow, intraabdominal, and intrathoracic regions. Paucity of mechanical adipose tissue in the palms, soles, orbits, scalp, and periarticular regions was noted in CGL2, whereas it was well preserved in CGL1 patients. The authors concluded that congenital generalized lipodystrophy patients with BSCL2 (606158) mutations have a more severe lack of body fat, which affects both metabolically active and mechanical adipose tissue.

Haghighi et al. (2016) compared the clinical features of 5 patients with genetically confirmed CGL1 and 5 with CGL2. All patients had generalized lipodystrophy and muscular hypertrophy, and most had hepatomegaly and splenomegaly. Additional features were found in both groups, but tended to be more frequent in patients with CGL2 than in those with CGL1; these features included acromegaloid appearance, large ears, triangular facies, acanthosis nigricans, increased insulin levels, elevated liver enzymes, hernias, and cardiomyopathy. Genital abnormalities and hypertriglyceridemia were found equally in both groups. Two CGL1 patients and 1 CLG2 patient had nephrolithiasis. Only 1 CGL1 patient had bone cysts, and only CGL2 patients had intellectual disability, hypertrichosis, and high-pitched voice.

Clinical Management

Seip and Trygstad (1996) urged that patients with congenital lipodystrophy avoid excessive food intake. They should have 4 regular meals a day and avoid large meals because they have limited ability to store energy as fat, lacking the buffer capacity of a normal adipose organ. They considered it unimportant whether calories are given as carbohydrate or fat. Easily digestible carbohydrates should be restricted, and dietary fiber is important.

Ebihara et al. (2007) treated 7 Japanese patients with generalized lipodystrophy, 2 acquired and 5 congenital type, with the physiologic replacement dose of recombinant leptin during an initial 4-month hospitalization followed by outpatient follow-up for up to 36 months. The leptin-replacement therapy with the twice-daily injections dramatically improved fasting glucose (mean +/- SE, 172 +/- 20 to 120 +/- 12 mg/dl, P less than 0.05) and triglyceride levels (mean +/- SE, 700 +/- 272 to 260 +/- 98 mg/dl, P less than 0.05) within 1 week. Ebihara et al. (2007) concluded that their study demonstrates the efficacy and safety of the long-term leptin replacement therapy and possible mechanisms of leptin actions in patients with generalized lipodystrophy.

Heterogeneity

Rajab et al. (2002) presented evidence for at least 1 further form of congenital generalized lipodystrophy that did not show involvement of either of the 2 loci, AGPAT2 (603100) and BSCL2 (606158). Rajab et al. (2002) reported observations on 17 patients with congenital generalized lipodystrophy in Oman which suggested the existence of a rare form of the disorder. All children had widespread absence of adipose tissue from infancy together with apparent muscle hypertrophy and hepatomegaly. The patients did not appear to represent a single homogeneous entity, and could be subclassified into 2 distinct groups. One group of 7 patients had features similar to other published cases with acanthosis nigricans, raised insulin levels, and insulin resistance. In this group there was an association between the degree of acanthosis nigricans and the severity of the disorder. Molecular analysis of these cases showed homozygosity for a mutation at the BSCL2 locus on 11q13 in 4 of the 7 cases. Rajab et al. (2002) described a second group of 10 patients who also had striking abnormalities in both skeletal and nonskeletal muscle, including reduced exercise tolerance, and percussion myoedema. These latter patients were later found by Rajab et al. (2010) to have mutations in the PTRF gene (603198) consistent with CGL4 (613327).

Agarwal et al. (2003) genotyped 45 pedigrees with CGL for AGPAT2 and BSCL2 loci and compared the phenotypes in the various subtypes. Twenty-six pedigrees harbored mutations, including 7 novel variants, in the AGPAT2 gene, and 11 pedigrees harbored mutations in the BSCL2 gene, including 5 novel variants. Eight pedigrees had no substantial alterations in either gene. Of these, 3 informative pedigrees showed no linkage to markers spanning the AGPAT2 and BSCL2 loci, and in 6 of the affected subjects, the transcripts of AGPAT2 and BSCL2 were normal. All subtypes of CGL showed high prevalence of diabetes, hypertriglyceridemia, and acanthosis nigricans. However, patients with BSCL2 mutations had lower serum leptin levels, an earlier onset of diabetes, and higher prevalence of mild mental retardation compared with other subtypes. The authors concluded that besides AGPAT2 and BSCL2, there may be additional loci for CGL and that genetic heterogeneity in CGL patients is accompanied by phenotypic heterogeneity.

Among 4 BSCL patients in whom no mutations in either AGPAT2 or seipin had been found, Kim et al. (2008) found a premature termination mutation in the CAV1 gene (601047.0001) in one (BSCL3; 612526). The sequences of all 3 of these genes were normal in the other 3 patients, suggesting that mutation in at least one other gene is responsible for the phenotype.

Mapping

Using a semiautomated genomewide scan with a set of highly polymorphic short tandem repeats in 17 well-characterized BSCL pedigrees, Garg et al. (1999) identified a locus on chromosome 9q34. The maximum 2-point lod score was 3.6 at D9S1818 (theta of 0.05). There was evidence for genetic heterogeneity (alpha of 0.73), and 2 of the pedigrees were unlinked. Multipoint linkage analysis excluding the 2 unlinked families yielded a peak lod score of 5.4 between D9S1818 and D9S1826.

Molecular Genetics

In affected members of 11 pedigrees with autosomal recessive Berardinelli-Seip congenital lipodystrophy showing linkage to 9q34, Agarwal et al. (2002) identified 11 mutations in the AGPAT2 gene (see, e.g., 603100.0001-603100.0005). All affected members carried homozygous or compound heterozygous mutations.

Fu et al. (2004) screened for mutations in AGPAT2 and BSCL2 (606158) in 27 families with congenital generalized lipodystrophy. They found mutations in either AGPAT2 or BSCL2 in all but 4 probands, including 3 novel mutations in AGPAT2, lys215 to ter (603100.0006), IVS3-1G-C (603100.0007), and phe189 to ter (603100.0008). In 3 sibs with congenital generalized lipodystrophy and cystic angiomatosis of the long bones, a phenotype designated Brunzell syndrome, they identified a splice site mutation in AGPAT2 (IVS4-2A-G; 603100.0002). The authors concluded that there did not appear to be any distinguishing clinical characteristics between congenital generalized lipodystrophy subjects with AGPAT2 or BSCL2 mutations, with the exception of mental retardation in carriers of BSCL2.

Agarwal et al. (2002) pointed out that individuals with congenital generalized lipodystrophy type 2 who carry mutations in the BSCL2 gene tend to have mild mental retardation and cardiomyopathy, features not seen in families with congenital generalized lipodystrophy type 1 who have mutations in the AGPAT2 gene. Based on the high expression of seipin in brain and weak expression in adipocytes, Magre et al. (2001) suggested a primary defect in hypothalamic pituitary axis. Agarwal et al. (2002) suggested that different forms of congenital generalized lipodystrophy may be caused by disruption of different pathways.

Animal Model

Shimomura et al. (1998) produced transgenic mice that overexpressed nuclear Srebp1c (184756) in adipose tissue under the control of the adipocyte-specific Ap2 (600434) enhancer/promoter. These mice exhibited many of the features of congenital generalized lipodystrophy. White fat failed to differentiate fully, and the size of white fat deposits was markedly decreased. Brown fat was hypertrophic and contained fat-laden cells resembling immature white fat. Levels of mRNA encoding adipocyte differentiation markers, including leptin (164160), were reduced, but levels of Pref1 (176290) and TNF-alpha (191160) were increased. Transgenic mice had marked insulin resistance, with 60-fold elevation in plasma insulin. Diabetes mellitus with elevated blood glucose of greater than 300 mg/dl that failed to decline when insulin was injected was observed. Transgenic mice had fatty liver from birth and developed elevated plasma triglyceride levels later in life. Shimomura et al. (1999) demonstrated that insulin resistance in the lipodystrophic mice could be overcome by continuous systemic infusion of low doses of recombinant leptin, an effect that was not mimicked by chronic food restriction.

Shimomura et al. (1999) concluded that their results supported the idea that leptin modulates insulin sensitivity and glucose disposal independently of its effect on food intake, and that leptin deficiency accounts for the insulin resistance found in congenital generalized lipodystrophy.

History

Lie (1996) gave a tribute to Seip on his seventy-fifth birthday.