A netlike rash.

Abstract

QUESTION: A 59-year-old man is seen because of a netlike rash in the sacral area. The rash began 2 months ago and was neither pruritic nor painful. The patient has a long history of arthritis and back pain. On physical examination, a hyperpigmented reticulated rash is seen on the sacral area (figure). What additional history would help to make this diagnosis? ANSWER: Additional history revealed that the patient started using a heating pad to soothe his back pain about the same time the reticulated rash began to appear. The patient has erythema ab igne (“red from fire”), also known as toasted-skin syndrome, heat-induced circum-scribed dermal melanosis, fire stains, ephelis ignealis, or livedo reticularis e calore. Erythema ab igne is a cutaneous disorder caused by absorption of infrared radiation. Women are affected more often than men.1 Patients have a history of repeated exposures to heat at a lower level than that which causes a thermal burn. The skin is often mildly erythematous initially, but after repeated heat exposures, the classic blue, purple, or brown reticulated hyperpigmentation develops.1 Because of the general availability of central heating, erythema ab igne is less common in the United States than in countries where open fires are commonly used for heating. Historically, this condition was often seen on the inner thighs and legs of women who sat in front of a stove or open fire.1,2 Currently, it is most commonly seen in this country following repeated use of hot water bottles, infrared lamps, and heating pads. Erythema ab igne has been reported to appear on the legs following prolonged, daily exposure to a car heater. Occasionally, the first sign of splenomegaly, pancreatitis, pancreatic cancer, and other cancers is erythema ab igne resulting when patients apply external heat to relieve the underlying pain.2 Work exposure to heat (such as for bakers, silversmiths, and boiler operators) may cause this condition.1