Urticaria pigmentosa is a rare disease; probably less than 350 cases have been reported in the literature. The first case was described by Nettleship1 in 1869. Since that date, Little,2 in 1905, has collected reports of 154 cases and Finnerud,3 reports of 141 cases occurring between the years 1905 and 1923.
The disease usually begins in infancy and frequently disappears at puberty, but it may continue into adult life. Little states that 14 per cent of the cases do not develop until after the patients have reached the age of puberty, while Finnerud's figures show 33.9 per cent of cases of this type. In a few instances, cases have been observed following vaccination and varicella; others have followed a fright (Little). In the majority of cases, especially those developing in infancy, the earliest visible lesions are urticarial. These are soon followed by either macules, nodules