Molecular typing of the HLA-DRB1 gene associated with hypoaglycemia due to endogenous autoimmune hyperisulinism (Hirata syndrome)

Abstract

Insulin autoimmune syndrome (IAS), called Hirata disease, is a rare endocrine condition characterized by episodes of hypoglycemia due to the presence of high titers of autoantibodies against insulin. IAS is a form of immune-mediated hypoglycemia, which develops when a triggering factor (medication or viral infection) acts on an underlying predisposing genetic background. Certain rare diseases, especially of an autoimmune nature, are associated with particular types of polymorphisms in HLA class II genes such as the HLA-DRB1 gene. In a family whose pregnant woman was diagnosed with IAS, we proposed to determine the association between polymorphisms in the HLA-DRB1 gene and IAS.

To determine the association of molecular genetic markers in the HLA-DRB1 gene associated with this pathology, the DNA of each of the members of the family was analyzed by direct sequencing of exon 2 of the HLA-DRB1 gene using the Sanger method.

We identified the genotypes in the family members: the mother is a carrier of the alleles (HLA-DRB1*03/HLA-DRB1*04) in compound heterozygosis, the father was identified as homozygous for the HLA-DRB1*08 allele and the daughter compound heterozygous for alleles (HLA-DRB1*04/HLA-DRB1*08). Genetic counseling was carried out, with special interest in the minor carrying the DRB1*04 allele related to susceptibility to developing IAS when exposed to triggering agents in the future.

The HLA-DRB1*04 allele would represent an immune-genetic marker that would help explain the endocrine and molecular mechanisms involved in the development of IAS. This is the first case described in which a pregnant patient with IAS gives birth to a healthy baby heterozygous for the gene associated with IAS.