Long QT syndrome with insulin-dependent diabetes mellitus: contiguous gene syndrome on chromosome 11p.

Long QT syndrome (Romano-Ward syndrome) and insulin-dependent diabetes mellitus (IDDM) have been documented as being linked with gene(s) on chromosome 11p although concurrence of the two disorders has not been reported. Our case is a 13-year-old boy with Romano-Ward syndrome accompanied by IDDM. The long QT syndrome seemed to be transmitted in an autosomal-dominant mode because the Q-T intervals of his father and paternal grandfather were longer than normal. There was no family member with an abnormally high level of blood glucose except the patient. The human leucocyte antigen (HLA) haplotypes of the patient and the father were DR4/DR9 and DR2/DR9, respectively. This study suggests that in our patient IDDM, as well as Romano-Ward syndrome, is linked with chromosome 11p in the presence of HLA-DR4. The results support the previous study that chromosome 11p encodes a gene implicated in HLA-DR4-dependent diabetes susceptibility.