Ataxia-telangiectasia in a patient presenting with hyper-immunoglobulin M syndrome.

Ataxia-telangiectasia (AT) and hyper-immunoglobulin M (HIGM) syndrome are both primary immunodeficiency diseases caused by different genetic defects. While a small proportion of AT patients have increased serum immunoglobulin (Ig) M concentrations during the course of a disease, a high level of IgM at onset is rare. We report the case of an 8-year-old girl who had experienced recurrent respiratory infection, cutaneous abscesses, and hepatosplenomegaly since the age of 2 years. She was diagnosed with HIGM based on the results of immunological studies, including low IgG and IgA levels and raised serum IgM concentrations. However, at the age of 4 years, a neurological examination revealed gait disturbance and telangiectatic lesions on the conjunctiva; therefore, a diagnosis of AT was suggested. In spite of regular intravenous immunoglobulin infusions and antimicrobial prophylaxis, the patient experienced several episodes of respiratory infection and eventually died of respiratory failure at the age of 8 years. Further molecular analysis revealed a novel homozygous missense mutation in exon 53 (c.8250C>T, p.2622Ala>Val) of the ATM gene. Patients with AT and the HIGM phenotype may not develop clinical characteristics of AT for some time. While patients with AT and increased serum IgM levels could have a considerably more severe disease course and a shorter survival, IgM levels could be considered a prognostic factor.