Erythema ab Igne After Frequent Heating Pad Use

A 62-year-old woman presented with a rash and intermittent pain of the right upper quadrant. The reticular, brown hyperpigmentation was also seen on her right flank and around the umbilicus. The patient reported that she often applied heating pads to these areas for pain relief.

A CT scan of the abdomen and pelvis revealed a mass in the cecum and multiple small metastases in the liver. A fungating cecal lesion was found on colonoscopy; a biopsy confirmed a poorly differentiated adenocarcinoma of the colon, stage IV. The patient was offered only palliative care.

Drs Mubashir Shah and Khalid Aziz of the University of Connecticut, Farmington, write that the rash was erythema ab igne-an infrared radiation–induced dermatosis. After long-term exposure to a heat source, initial bands of erythema develop into a distinctive brown, hyperpigmented, reticular rash, which may fade but can be permanent. Generally, the condition is painless and does not blister. Advise the patient to discontinue use of the heat source; corticosteroids may be tried.

Differentiate erythema ab igne from livedo reticularis, which features a reddish purple-not brown-reticular pattern. Livedo reticularis is associated with leukocytoclastic vasculitis, collagen vascular disease, and antiphospholipid antibody syndrome.

There is a small risk of malignant transformation from erythema ab igne to squamous cell carcinoma of the skin. Coexisting Merkel cell carcinoma and squamous cell carcinoma in areas of erythema ab igne have been attributed to long-term exposure to thermal radiation.

FOR MORE INFORMATION:

• Hewitt JB, Sherif A, Kerr KM, Stankler L. Merkel cell and squamous cell carcinomas arising in erythema ab igne. Br J Dermatol. 1993;128:591-592.

• Meffert JJ. Environmental skin diseases and the impact of common dermatoses on medical readiness. Dermatol Clin. 1999;17:1-17.

• Peterkin GA. Malignant change in erythema ab igne. Br Med J. 1955;2:1599-1602.