Diabetes Mellitus, Insulin-Resistant, With Acanthosis Nigricans

A number sign (#) is used with this entry because insulin-resistant diabetes mellitus with acanthosis nigricans can be caused by heterozygous, homozygous, or compound heterozygous mutation in the INSR gene (147670) on chromosome 19p13.

Clinical Features

Kahn et al. (1976) divided the syndrome of insulin resistance and acanthosis nigricans into two: type A, a syndrome of younger females with signs of virilization and accelerated growth in whom a defect in cell receptors for insulin 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. Although no familial cases were found, they commented that all their patients and those in the literature were female; most were black, although the syndrome has been observed in persons of American Indian, Italian, Venezuelan, and Japanese origin. Despite insulin resistance, ketoacidosis was rare. Females with the type A syndrome have polycystic ovaries.

Rudiger et al. (1983) described 3 sibs with mild diabetes in combination with acanthosis nigricans and minor physical abnormalities: bitemporal narrowing of the skull, paucity of body fat, acral hypertrophy (enlarged ears, nose, chin, and finger tips), brachydactyly, protrusion of the eye globes, and dental anomalies (supernumerary teeth, severe and premature caries, abnormally prominent lower canines and upper incisors). Fasting plasma insulin was 100 times normal. Insulin-binding was defective. Scatchard analysis showed a normal number of insulin-binding sites per cell but a complete lack of insulin binding to the high-affinity receptor component.

In patients with an inherited affinity defect of the insulin receptor, Rudiger et al. (1985) found that stimulation of glucose uptake, an early effect of insulin, was normal, but insulin-mediated stimulation of RNA synthesis, a late effect, was defective. Both the affinity defect and the deficient stimulation of RNA synthesis were apparent at low concentrations of insulin only and disappeared at very high concentrations.

Mariani et al. (1982) described a 6.3-year-old girl with acanthosis nigricans, insulin-resistant diabetes mellitus, hypertelorism, prognathism, macroglossia, and large ears. Generalized hypertrichosis and hypertrophy of the clitoris were present. A decrease in the number of insulin receptors was demonstrated. In the patient reported by Leme et al. (1982), polycystic ovaries were also present. Insulin resistance with acanthosis nigricans but with normal receptors may have a postreceptor defect (Bar et al., 1978). Prince et al. (1986) studied a 15-year-old black female with menstrual irregularity, mild hirsutism, and marked acanthosis nigricans that was first noted at age 4 years. Insulin receptors on cultured fibroblasts were decreased and the remaining receptors showed a functional impairment. Perhaps one should speak of types A1 and A2 of insulin-resistance and acanthosis nigricans (IRAN), type A2 being a form with a postbinding defect.

Grigorescu et al. (1984) and Grunberger et al. (1984) described patients with type A insulin resistance and decreased insulin receptor kinase activity. In 2 patients with type A extreme insulin resistance, sisters who were the products of a consanguineous marriage, Ojamaa et al. (1988) found normal levels of insulin receptor mRNA. They had previously shown that the insulin receptor precursor is synthesized at a normal rate in these patients, thus suggesting a defect in the posttranslational processing of the receptor or in its translocation to the plasma membrane. See review by Kahn and White (1988).

Schwenk et al. (1986) observed acanthosis nigricans in a white family; the mother and 3 daughters (including a set of identical twins) had acanthosis nigricans. Three sons were normal. Two of the 4 affected females had no apparent ovarian dysfunction, whereas 2 had hyperprolactinemia without other findings of polycystic ovary disease (184700). The twins had muscle cramps (see 200170). All had normal red cell and monocyte binding of insulin. Insulin responsiveness, on the other hand, was reduced, suggesting a postbinding defect. They raised the question of autosomal dominant inheritance.

Seemanova et al. (1992) investigated a family in which at least 4 men in 3 generations had a syndrome of obesity, mild mental retardation, delayed puberty, macroorchidism, acanthosis nigricans, hyperinsulinemia, and, later, overt insulin-resistant diabetes mellitus (noninsulin-dependent diabetes mellitus, or type II diabetes). The patients had markedly curly scalp hair and deficient hair of the face and body. Teeth were normal. There was normal insulin binding to fibroblasts; however, insulin-stimulated RNA synthesis was decreased as compared to that of normal control individuals, suggesting a postbinding defect in insulin action. The pedigree showed an autosomal dominant pattern of inheritance.

Molecular Genetics

In a young Japanese male with insulin-resistant diabetes mellitus and acanthosis nigricans, Odawara et al. (1989) identified a mutation in the INSR gene (147670.0001).

Among 22 unrelated women with insulin resistance, acanthosis nigricans, and the polycystic ovary syndrome (hyperandrogenemia, oligoamenorrhea, and hirsutism), Moller et al. (1994) identified only 1 mutation in the INSR gene: arg1174 to gln (147670.0030). Moller et al. (1994) concluded that mutation in the INSR gene is a rare cause of the type A syndrome of extreme insulin resistance.

Acanthosis nigricans in association with insulin resistance behaves as either a dominant (e.g., 147670.0001) or a recessive (e.g., 147670.0004). The polycystic ovary syndrome is sometimes associated. The autosomal dominant mutations in the insulin receptor gene are 'dominant negatives;' the mutant receptor protein interferes with the function of the normal receptor.

Associations Pending Confirmation

Dash et al. (2009) screened 156 severely insulin-resistant patients with acanthosis nigricans for mutations in the candidate gene TBC1D4 (612465) and identified a 23-year-old woman who was heterozygous for a nonsense mutation (R363X; 612465.0001). The mutation was present in her affected half sister, as well as in their mother and a maternal aunt, neither of whom exhibited acanthosis nigricans but who did have a disproportionate rise in insulin following oral glucose load. Their maternal grandmother, who also carried the mutation, showed a normal peak-to-fasting insulin ratio but had an elevated fasting glucose and impaired glucose tolerance, indicative of significant beta-cell dysfunction. The mutation was not found in an unaffected aunt who was obese but had normal glucose tolerance and a normal peak-to-fasting insulin ratio, or in 200 ethnically matched alleles.