Evidence purporting that the so-called hypomelanosis of Ito (HI) syndrome does not exist as a distinct multisystem birth defect is presented by geneticists and dermatologists at Bad Salzschlirf, and Philipp University of Marburg, Germany. HI is a nonspecific pigmentary disorder representing a cutaneous marker of many different states of genetic mosaicism. The clinical findings are highly variable, not always involving brain, eyes or bones, occurrence is sporadic, and cytogenetic abnormalities involve many different chromosomes, especially the X-chromosome. The terms HI, incontinentia pigmenti achromians, pigmentary dysplasia, and pigmentary mosaicism are synonyms of the same cutaneous signs. “Pigmentary mosaicism of the Ito type” should be substituted for the term “HI syndrome.” [1]

COMMENT. HI is a relatively common disorder in pediatric neurology clinics, involving 1 in every 1000 patients attending a service in Spain [2]. CNS anomalies include mental and motor retardation, microcephaly, hypotonia, hyperkinesia, ataxia, seizures, and deafness. Eye defects include microphthalmia, ptosis, nystagmus, cataracts, and retinal degeneration. Bone anomalies include dental enamel defects, short stature, limb asymmetry, scoliosis, syndactyly, and Polydactyly. These multisystem defects are explained, not as a single syndrome, but by different genetic defects and a sign of mosaicism, as evidenced by a variety of reported underlying chromosomal abnormalities.