• erythema nodosum
• chancroid

Erythema nodosum is a type of panniculitis which is often regarded as a complex reaction pattern to various aetiological factors of infective and non-infective origin.¹ Infective agents outnumber inflammatory causes and drugs in causation of erythema nodosum in the developing countries. Almost all the infective agents including aerobic and anaerobic bacteria, viruses, fungi, parasites and mycobacteria can induce eruption of erythema nodosum.² Among sexually transmitted infections lymphogranuloma venereum has been known to be associated with erythema nodosum not infrequently.³

A 23 year old woman presented with genital ulcer disease and painful rash over the legs of 1 week’s duration. There was no history of trauma, fever, or drug intake. She had a single stable sexual partner who was apparently unaffected. Examination revealed a single, 1–1.5 cm size, irregular tender ulcer on the right labia minora with undermined margins and bleeding on touch. The right inguinal lymph nodes were firm, moderately enlarged, and tender. Speculum and vaginal examination was normal. Examination of the perianal region, perineum, and other mucosae was also normal.

Multiple tender, erythematous nodular subcutaneous lesions with dusky erythema were present over both shins, calves, and ankle joints. Investigations revealed a normal complete blood count, serum biochemistry, urinalysis and blood sugar. VDRL, HIV-1 ELISA, and HBsAg were negative. Dark ground illumination, smears, and cultures from the ulcer did not reveal aetiological diagnosis. Histopathology from the ulcer revealed an ulcerated surface with necrosis and neutrophilic infiltrate deeper to which a zone of new blood vessel formation with marked endothelial proliferation and a lymphoplasmacytic infiltrate was observed. These features were consistent with diagnosis of chancroid while histopathology of leg lesions confirmed it to be septal panniculitis consistent with a diagnosis of erythema nodosum. The patient was treated with erythromycin stearate 500 mg 6 hourly for 7 days. The genital ulcer healed completely in 7–10 days but the lesions of erythema nodosum subsided completely in 5–7 days without any other treatment.

Erythema nodosum as a cutaneous reaction pattern was first observed by Willan in 1798.⁴ A female preponderance with a ratio of 3:1 is often observed in adults compared to an equal incidence at prepubertal age. Although the exact pathogenesis of erythema nodosum is not known, it has been regarded as a immune complex, deposition disease which prefers the richly supplied vascular adipose tissue of the legs.

In the present patient erythema nodosum and chancroid had a strong temporal correlation as erythema nodosum immediately followed the appearance of the chancroid and resolved completely with its resolution. Although erythema nodosum is known to be associated with innumerable infective agents, to the best of our knowledge chancroid leading to causation of erythema nodosum has not been observed before.