Shapiro and Yen (1987) responded to the suggestion that the condition in these patients may represent a microcytogenetic disorder ( Schmickel, 1986 ). They stated that homologous but nonfunctional sequences of STS were found on the long arm of the Y chromosome in the patients of Sunohara et al. (1986) . Indeed, they found a complete deletion of the STS gene with continued presence of MIC2 ( 313470 ) sequences, which are located more distally on the X chromosome, in both the X and Y chromosomes. In studies of 9 unrelated patients with simple X-linked ichthyosis, they found 7 with complete deletion of the STS gene and 1 with a partial 5-prime deletion. Only 1 subject had an intact STS gene.