We report two cases of hypomelanosis of Ito. Case 1) A 7-month-old boy presented with mitral incompetence, opened arterial ligament of right aortic arch, cryptorchidism, left-ear deafness, overlap of both 5th fingers, and unusual facial contours since birth. Tenioid hypopigmented whorls or streaks following Blaschko lines were found on the trunk and limbs with Unna's nevus on the forehead and the regio occipitalis capitis. Erythema or vesicles were not observed throughout his clinical course. We diagnosed the patient as hypomelanosis of Ito. A chromosomal analysis was normal, and magnetic resonance imaging of the head showed no apparent abnormalities. Histologically, Fontana-Masson staining showed a decreased concentration of melanin granules in the region of the hypopigmentation without any incontinentia pigmenti. In the affected hypopigmented area, a marked decrease of c-KIT-, MITF- and tyrosinase-positive cells was evident compared with the surrounding normal skin. Case 2) A 1-year-old girl presented with aproctia, both talipes calcaneovalgus, syndactyly of the right 3rd, 4th and 5th toes, syndactyly of the left 4th and 5th toes and left hypoplastic kidney since birth. Tenioid hypopigmented whorls or streaks following Blaschko lines were observed on the limbs, leading to a diagnosis of hypomelanosis of Ito. Hypomelanosis of Ito is frequently associated with serious complications such as abnormalities of the central nervous system. Careful dermatological observation is mandatory for diagnosing hypomelanosis of Ito.
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