Diagnosis: erythema nodosum, a hypersensitivity reaction
The patient’s presentation and clinical findings suggest erythema nodosum. Erythema nodosum is one of several hypersensitivity syndromes. It is likely a delayed hypersensitivity reaction and may be triggered by a number of antigens.
Painful, erythematous nodules on both shins are characteristic of erythema nodosum, though similar lesions occur on other extensor surfaces.1Panniculitis is often used to describe this condition, as pathologic evaluation demonstrates inflammation within the subcutaneous fat.
The nodules generally resolve over several weeks with possible desquamation on the lesion’s surface. Patients may have a prodrome of fever, arthralgias, and often symptoms of an upper respiratory infection occurring 2 to 8 weeks before the eruptive phase.1,2
Erythema nodosum may occur as a result of bacterial and fungal infections. Many medications have also been known to cause erythema nodosum, with sulfa drugs and oral contraceptives among the most common. The condition may also herald systemic disease, such as sarcoidosis or inflammatory bowel disease.
The photographs show the characteristic erythematous eruptive phase in its early stage. The lesions progress from tender erythematous areas with a nodular texture to become yellowish-purple and bruiselike. The lesions generally resolve over several weeks.
Approximately 50% of cases are idiopathic. Erythema nodosum can affect persons at any age but appears most often in those in their twenties and thirties. It affects women 3 to 6 times more frequently than men.1,2