An infant with an XXXYY karyotype

Abstract
An infant with mild retardation of psychomotor development and ambiguous genitalia was found to have a 49, XXXYY karyotype. The identity of the chromosomes was established by different banding methods, both fluorescent and non‐fluorescent. An attempt was made to find the origin of the extra X chromosomes by testing the Xg blood group in the whole family. An evaluation of the clinical features exhibited by male patients with different sex chromosome configurations is given in relation to the excess of X and Y chromosomes.