Ataxia-telangiectasia: A review of clinical features and molecular pathology.

Ataxia-telangiectasia (A-T) is an autosomal recessive primary immunodeficiency (PID) disease that is caused by mutations in ataxia-telangiectasia mutated (ATM) gene encoding a serine/threonine protein kinase. A-T patients represent a broad range of clinical manifestations including progressive cerebellar ataxia, oculocutaneous telangiectasia, variable immunodeficiency, radiosensitivity, susceptibility to malignancies, and increased metabolic diseases. This congenital disorder has phenotypic heterogeneity, and the severity of symptoms varies in different patients based on severity of mutations and disease progression. The principal role of nuclear ATM is the coordination of cellular signaling pathways in response to DNA double-strand breaks, oxidative stress, and cell cycle checkpoint. The pathogenesis of A-T is not limited to the role of ATM in the DNA damage response (DDR) pathway, and it has other functions mainly in the hematopoietic cells and neurons. ATM adjusts the functions of organelles such as mitochondria and peroxisomes and also regulates angiogenesis and glucose metabolisms. However, ATM has other functions in the cells (especially cell viability) that need further investigations. In this review, we described functions of ATM in the nucleus and cytoplasm, and also its association with some disorder formation such as neurologic, immunologic, vascular, pulmonary, metabolic, and dermatologic complications.