Ataxia Telangiectasia Arising as Immunodeficiency: The Intriguing Differential Diagnosis.

Ataxia telangiectasia (AT) is a rare disease characterized by the early onset and slow progression of neurodegenerative defects, mainly affecting the cerebellum, associated with immunodeficiency and teleangiectasias. Ataxia is the hallmark of the disease and usually its first manifestation. Overt cerebellar ataxia usually becomes evident between 16 and 18 months of age, after the onset of walking, and is characterized by frequent falls and an ataxic gait with an enlarged base. We report the case of a child who first presented with serious recurrent infectious, without exhibiting neurological symptoms. The patient was initially diagnosed with combined immunodeficiency (CID) of unknown etiology for nearly 3 years, before he was definitively diagnosed with ataxia telangiectasia.