Tuberculosis-Associated Erythema Nodosum.

Erythema nodosum is panniculitis that is frequently observed in women aged 18 to 34 years. It usually occurs as an idiopathic condition; however, it may be associated with drugs, infections, malignancy, pregnancy, and systemic illnesses. Erythema nodosum presents with the sudden onset of tender, warm, erythematous nodules typically on the ankles, knees, and shins. Although the pathogenesis has not been fully elucidated, evidence supports a delayed type IV hypersensitivity reaction. It is often a clinical diagnosis that does not require a biopsy; appropriate work-up and careful medication history are crucial to identifying an underlying etiology if present. This report describes a woman from Vietnam, a tuberculosis endemic country, who presented with erythema nodosum that was determined to be a sequela of latent tuberculosis. Several studies have demonstrated an association between erythema nodosum and tuberculosis, especially in endemic regions. Summarized data reveals the incidence of tuberculosis-associated erythema nodosum to be six percent; however, when individuals with either secondary erythema nodosum or infection-associated erythema nodosum are evaluated, the incidence of tuberculosis-associated erythema nodosum is 11% or 21%, respectively. Evaluation of erythema nodosum should include a tuberculin or QuantiFERON test, chest roentgenogram, and/or an acid-fast bacilli sputum culture if the diagnosis of tuberculosis is being considered.