74 下列有關hereditary ataxia-telangiectasia的情況，何者正確？

為X-linked遺傳

細胞染色體斷裂於T cell receptor及immunoglobulin heavy chain之處，並且有嚴重的T細胞缺乏

造成adenosine deaminase deficiency

亦有MHC II分子表現之缺陷

ans B

Ataxia-telangiectasia (AT) is a genetic disease characterized by progressive cerebellar ataxia, oculocutaneous telangiectasia, and recurrent respiratory and sinus infections.

Pathophysiology

Ataxia-telangiectasia mainly is due to a defect in a DNA processing or repair protein. The cerebellar and extrapyramidal systems are the most severely affected. This syndrome is characterized by a severe loss of Purkinje cells and, to a lesser degree, the basket and granular cells of the cerebellar cortex. Other pathological changes include cerebellar cortical atrophy, diffuse fibrillary gliosis, and degeneration of the anterior horn cells of the spinal cord. Studies have revealed reduced levels of cerebellar neurotransmitters, including phosphoethanolamine, gamma-aminobutyric acid (GABA), and glutamic acid.