Clinical Manifestations of Ataxia-Telangiectasia with Class Switch Recombination Defect

Elevated serum levels of IgM and recurrent infections, mainly respiratory tract infections, could be the presenting features in some ataxia-telangiectasia (AT) patients, and may initially be misdiagnosed as hyper-IgM (HIgM) syndrome. Class switch recombination (CSR), which is defective in HIgM syndrome, is an important mechanism in the maturation of B lymphocytes to produce different isotypes of antibodies in response to antigen stimulation.

The clinical manifestations and laboratory findings of 16 cases with low IgA and IgG levels, and normal to elevated IgM levels with CSR defect are reported.

In 16 cases, the median age at onset of the diseases, and median age at the time of the diagnosis were 1 year (interquartile range [IQR] = 1.6), and 4 years (IQR = 3.1), respectively. Two of the patients (12.5 %) died due to respiratory infection. In this study, Out of the studied population, four were male (25%), and 12 were female (75%). Most of the patients had consanguineous parents (81.3 %). All of the patients had ataxia, and 15 patients had telangiectasia (93.8 %), and one of the cases had malignancy (dermatofibroma). Also, 15 patients presented infections (93.8 %). Autoimmunity was seen in three patients (18.8 %). In addition, some of the patients manifested hepatosplenomegaly (31.3 %) and thrombocytopenia (18.8 %). Neurological manifestations, such as visual impairment (12.5 %), epilepsy (6.3 %), and tremor (12.5 %), were also present.

AT patients with HIgM phenotype and CSR defect, compared to other AT patients, may present different clinical manifestations, such as various infections. Considering their manifestations, the management and treatment of these patients are necessary.