49, XXXYY Syndrome

49, XXXYY syndrome, also known as XXXYY syndrome, is a chromosomal disorder first reported in 1963 (Benn et al. 1982). Key diagnostic features of this pentasomy include moderate to severe intellectual disability, global developmental delay, facial dysmorphisms, eunuchoid body proportions, normal to tall stature, gynecomastia, hypogonadism, cryptorchidism, micropenis, skeletal malformations, and behavioral abnormalities. Symptoms of this syndrome may appear in the first month of life. This syndrome is rare, with a prevalence of less than 1 per 1,000,000 (Cowie et al. 1986).