Ataxia-telangiectasia in twins presenting as autosomal recessive hyper-immunoglobulin M syndrome.

• Vol 9 • May 2007 406 Ataxia-telangiectasia is a rare autosomal recessive multisystem disorder characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia, recurrent sinopulmonary infection – all due to immune defects, and a high incidence of mainly B lymphoid malignancy [1]. Ataxiatelangiectasia results from mutations in a single gene, ataxia telangiectasia mutated (ATM). The protein product of the ATM gene is a serine-threonine kinase involved in cell cycle control, gene regulation, intracellular signaling and DNA repair. Recently, investigators partly clarified its role in the immune system by showing its importance in class-switch recombination, an essential step in the production of immunoglobulin A, G and E but not M [2]. While this explains the hypogammaglobulinemia observed in A-T, the exact mechanism that leads to the cellular immune defect in this disease is not yet understood. Progressive cerebellar ataxia is the presenting symptom in most cases, and in 70% telangiectasia appeared before the diagnosis was established. While recurrent bacterial infections due to immunodeficiency are common features, hypogammaglobulinemia as the only symptom of A-T is very rare. In the present study we report twin girls who were diagnosed as suffering from hyper-IgM syndrome without any