ABSTRACT
The diagnosis of hypomelanosis of Ito (HI) is appropriate in individuals with hypopigmented skin lesions on the trunk and limbs following the lines of Blaschko. HI was originally named incontinentia pigmenti achromians in 1952 by Ito because the nonrandom streaks, whorls, and patches seen in HI are often described as the ‘‘negative pattern’’ of the hyperpigmented skin lesions in the disorder incontinentia pigmenti. Ito first described the disorder as a cutaneous syndrome, but it now seems clear that 33-94% of individuals have associated neurological, ophthalmological, and other complications. Mental retardation and seizures are characteristically associated with CNS involvement in HI but there is extreme variability in the severity of disease. Recent evidence convincingly suggests that HI is not a discrete disorder as originally believed but instead a nonspecific pigmentary disorder caused by chromosomal mosaicism. HI almost always occurs sporadically, and it seems to be caused by a de novo mutation in early embryogenesis. Although HI is often considered the fourth most common neurocutaneous syndrome, its incidence is very rare, with only 1 in every 600-1000 new patients in a pediatric neurology service.
