From time to time during the past five years we have had the opportunity to observe an unusual type of eruption in two sisters who have been patients of Dr. Oliver S. Ormsby, through whose courtesy this study has been made possible. The disorder dates back to childhood in both cases, with periods of marked activity at irregular intervals. REPORT OF CASES Case 1.—History.—Mrs. D., of American birth and German descent, was born in 1902. Her first cutaneous trouble appeared at the age of 2 months as a generalized, bright red exanthem, which suggested prickly heat. At 6 months this became exfoliative and persisted until 2 years of age. From the age of 4 years to 12 years she had four similar attacks, each lasting several months. When 15 years of age, discrete psoriasiform lesions appeared for the first time on the elbows, the trunk and