先证者(Ⅰ_2),男,14岁,因行走不稳12年,反复咳嗽、发热8年于1978年6月住院。患儿系第2胎,足月顺产。7月会坐,1岁学走但易跌倒,双手持物抖动,不准确,11岁扶墙方能行走。生活不能自理。流涎不止,3岁讲话费力。从小易患感冒,身体虚弱。体检:发育营养差,双眼球结膜内外眦部可见扩张弯曲的毛细 Probability (I_2), male, 14 years old, due to unstable walking for 12 years, repeated cough, fever 8 years in June 1978 hospitalization. Children in the second child, full-term delivery. July will sit, 1-year-old to learn to walk but easy to fall, hands holding jitter, inaccurate, 11-year-old can only walk on the wall. Life can not take care of itself. More than drooling, 3-year-old speech laborious. From a small susceptible to a cold, frail. Physical examination: poor developmental nutrition, both eyes inside and outside the conjunctiva bulging curved capillary