PIK3CD and Prader-Willi syndrome: Meantime, 13.3% (12/90) of patients had underlying diseases: four had immune deficiency (two had agammaglobulinemia, one had chronic granulomatous disease, and one had PIK3CD gene mutation), while the other eight patients each had various underlying conditions such as chronic diarrhea with pancreas exocrine insufficiency, epilepsy, tuberous sclerosis, Prader-Willi syndrome, congenital bronchial stenosis muscular torticollis, bronchial asthma, congenital malformation (single kidney deficiency), and congenital heart disease (postoperative).