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.
It is a very rare condition with less than 1 case in every million births.
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.
The syndrome is associated with homozygous or compound heterozygous mutations in the insulin receptor gene (INSR; 19p13.3-p13.2).
A positive diagnosis requires identification of one mutation in each allele of this gene.
The differential diagnosis should include the other forms of extreme insulin resistance.
The disorder is transmitted as an autosomal recessive trait.
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 is uncertain, growth is severely affected and life expectancy rarely exceeds a few months.
Last update: January 2009