Leprechaunism

Leprechaunism is a congenital form of extreme insulin resistance (a group of syndromes that also includes Rabson-Mensenhall syndrome, type A insulin-resistance syndrome, and acquired type B insulin-resistance syndrome; see these terms) characterized by intrauterine and mainly postnatal severe growth retardation.

Epidemiology

It is a very rare condition with less than 1 case in every million births.

Clinical description

Leprechaunism is associated with a characteristic dysmorphic facies (resembling that of the 'leprechauns' in Irish folk traditions), atrophic subcutaneous adipose tissue (lipoatrophy) and muscular hypotrophy. Signs of virilization are often observed in young girls. Biologically, episodes of hypo- and hyperglycemia are observed along with marked hyperinsulinemia due to an extreme resistance to insulin.

Etiology

The syndrome is associated with homozygous or compound heterozygous mutations in the insulin receptor gene (INSR; 19p13.3-p13.2).

Diagnostic methods

A positive diagnosis requires identification of one mutation in each allele of this gene.

Differential diagnosis

The differential diagnosis should include the other forms of extreme insulin resistance.

Genetic counseling

The disorder is transmitted as an autosomal recessive trait.

Management and treatment

Treatment with recombinant insulin-like growth factor 1 (IGF1) may be considered. A combination treatment with insulin-like growth factor binding protein 3 (IGF-BP3) resulted in an increased lifespan in one case.

Prognosis

Prognosis is uncertain, growth is severely affected and life expectancy rarely exceeds a few months.