431- What are the differentiating features between type A and type B insulin
resistance?
Type A insulin resistance usually affects nonobese young women and is char-
acterized by the presence of acanthosis nigricans, features of androgen excess,
and hyperinsulinemia. Defect in insulin receptor or post-receptor signaling
pathway is the key abnormality in type A insulin resistance. Type B insulin
resistance is characterized by the presence of hirsutism, acanthosis nigricans,
and concurrent autoimmune disorders (e.g., SLE, scleroderma) in older women.
The presence of anti-insulin receptor antibody is the characteristic abnormality
in type B insulin resistance. The differentiating features between these two dis-
orders are summarized in the table given below.Parameters Type A insulin resistance Type B insulin resistance
Female: male 19:1 6:1
Age of onset Infancy or childhood Middle-aged or older women
Acanthosis nigricans Grade IV, diffuse Grade II–III
Concurrent disorders – Autoimmune disorders
Biochemistry Hyperglycemia
Hyperinsulinemia
HyperandrogenemiaHyperglycemia
Hyperinsulinemia
Hyperandrogenemia
ANA positivity
Treatment Insulin Steroids- What is leprechaunism?
Leprechaunism, also known as Donohue syndrome, is a disorder characterized
by severe insulin resistance. Affected newborns manifest characteristic elfin
facies, prenatal growth failure, severe acanthosis nigricans, features of andro-
gen excess (hirsutism, clitoromegaly in girls and macropenis in boys), diffuse
lipoatrophy, muscular hypotrophy, mental retardation, fasting hypoglycemia
with postprandial hyperglycemia, and marked hyperinsulinemia
(>1,000 pmol/L). Very high level of insulin which acts through the IGF1 recep-
tor is thought to be the cause of fasting hypoglycemia. Serum GH-IGF1 levels
may be low due to feedback inhibition by high levels of insulin acting through
IGF1 receptor at the hypothalamus. The disorder is inherited as an autosomal
recessive trait and is due to homozygous or compound heterozygous mutations
in insulin receptor gene which is located on chromosome 19. IGF1 therapy has
been shown to be effective in some of these patients. However, these infants
usually succumb to intercurrent infection within few months of their life
(Fig. 12.9).12 Diabetes in the Young