The natural history of polymorphous light eruptions.

The natural history of chronic, idiopathic polymorphous light eruption (PMLE( was studied in 138 patients, 85 of whom were female. Mean age of onset of the disease was 26.4 years, and the mean duration at the time of the study was 10.5 years. In most cases (57%) the onset of the disease was very sudden. Light hypersensitivity was usually first confined to limited skin areas, but often (88%) extended to further areas during subsequent summers. The light sensitivity tended to increase during the years; at the time of the study, the threshold tolerance to sun was 30 minutes or less for 60% of the patients. A yearly hardening phenomenon was noted by every second patient. Lip or eye symptoms were present in 46% and 49% of the patients, respectively. Two thirds of the patients experienced some general symptoms after sun exposure.