AbstractHypomelanosis of Ito (HI) is a congenital neurocutaneous syndrome presenting in the first year of life. It was first described by Ito in 1952 as a purely cutaneous disease presenting with skin hypopigmentation. Several extracutaneous manifestations were later described, and it is now known that several organs can be involved (including brain, muscle, bone, heart, eye, kidney, and teeth) and that the prognosis is strictly related to the number of involved organs. The incidence and prevalence of this syndrome have been estimated to range between 1 in 7,540 births and 1 in 82,000; the disorder affects both the sexes, occurs in all races, and is characterized by depigmentation of the skin along the lines of Blaschko on the trunk and extremities in whorled and linear streaks and patterns. The pathogenesis is unknown, but it is likely to be multifactorial. Several models of inheritance have been proposed but not proved; genetic mosaicism is nowadays the most likely explanation for its inheritance. The differential diagnosis comprises other disorders with hypopigmentation following the lines of Blaschko and thus includes the atrophic/hypopigmented (fourth) stage manifestations of incontinentia pigmenti of the Bloch–Sulzberger type, tuberous sclerosis complex, vitiligo, and skin fungal infections. Consensus recommendations for the screening of associated extracutaneous conditions do not exist and management is symptomatic, but a regular evaluation of somatic growth, neurodevelopment, endocrine status, eyes, and teeth should be performed, and the screening of renal function is also advisable. HI still represents a challenging disorder for the child neurologist and a controversial issue in the medical literature. Awareness of this disorder could allow an early diagnosis and appropriate genetic counseling and screening.
