The XXXXY syndrome has several distinctive phenotypic features, the most prominent of which are mental retardation and hypogonadism (small penis and small and/or undescended testes). Of the 61 cases of the XXXXY syndrome reviewed, not including the present case, all of the patients had severe mental retardation. Other characteristics include skeletal abnormalities, especially of the elbows and wrists, and clinodactyly of the fifth fingers.1-5
Despite the generally accepted contention that the probability of mental retardation increases proportionately with the number of X chromosomes present,2 the 15-month-old XXXXY boy reported here has a normal Gessell adaptive maturity level with only minor motor abnormalities.
Report of a Case
A male infant of Yugoslavian extraction was born on Nov 9, 1967. He was 8 weeks old when he was referred for evaluation of a peculiar facies and marked redundancy of the skin of the posterior cervical region.The mother was 27
Shapiro LR, Hsu LYF, Calvin ME, Hirschhorn K. XXXXY Boy: A 15-Month-Old Child With Normal Intellectual Development. Am J Dis Child. 1970;119(1):79–81. doi:10.1001/archpedi.1970.02100050081019
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