Streptococcal Exanthem in a Blaschkolinear Pattern: Clinical Evidence for Genetic Mosaicism in Hypomelanosis of Ito

: Due to the presence of two different clones of cells in early embryogenesis, numerous congenital and acquired dermatoses have a linear distribution following the lines of Blaschko. Acquired inflammatory skin diseases are rarely observed in linear patterns. Our patient was born with macrocephaly, left eye glaucoma, and a left facial and contralateral corporal hemihypertrophy, cerebral dysgenesis, and skeletal abnormalities. Hypopigmented S‐shaped linear macules on the trunk and linear streaks on the arms and legs were compatible with hypomelanosis of Ito. At 5 years of age the patient presented with an erythematous follicular exanthem compatible with scarlet fever exclusively in the lines of Blaschko. This fact suggests a genetic mosaicism.