Sparse scalp hair and erythematous rash in a girl

My patient a 6-years-old girl was born with scanty scalp hairs. As she grew old she developed light-coloured sparse, soft, uncombable hairs which broke down easily. The patients also gave history of itchy, erythematous lesions over her body since last 4 years. She had been developing infection in the lesions off and on. There was no history of any growth retardation, mental abnormality, teeth or nail defects. My patient was fourth among 4 sisters and 2 brothers. One of her elder brother, who was 10 years of age, was a patient of cerebral atrophy. Her parents were first cousins.