Editor,—Lymphatic filariasis is characterised by a wide range of clinical manifestations. In a non-endemic area the diagnosis may be missed unless the index of suspicion is high.Sex Transm Inf 2000;76:321–328

An 18 year old sexually active male presented with a progressively increasing painless nodular swelling in the right inguinal region of 4 months' duration. The patient had an unprotected vaginal contact with a commercial sex worker 6 months earlier. There was no history of genital ulcer or urethral discharge. The general health of the patient was preserved. Examination revealed enlarged right inguinal and external iliac lymph nodes, 1–3 cm in size, firm, mobile, non-tender, and matted with normal overlying skin. Examination of genital, anal, and buccal mucosae was normal. There was no other lymphadenopathy. A differential diagnosis of lymphogranuloma venereum (LGV) and tubercular lymphadenitis was considered. Complete blood count revealed mild leucocytosis and eosinophilia. Renal and hepatic functions, urinalysis, and chest x ray were normal. Mantoux test and VDRL were negative. A complement fixation test for chlamydia group specific antibody was negative. Fine needle aspiration cytology from the nodes revealed reactive hyperplasia with occasional giant cells and microfilariae of Wuchereria bancrofti. Nocturnal blood samples for microfilariae were negative.

The patient was given diethylcarbamazine 100 mg thrice daily for 2 weeks. The lymph nodes regressed and no relapse was observed in 6 months of follow up.

The differential diagnosis of inguinal lymphadenopathy in a sexually active male includes syphilis, genital herpes, chancroid, LGV, pyogenic adenitis, tuberculosis, and lymphoma.¹ In the present case a diagnosis of LGV was considered in view of a history of sexual contact, painless and non-suppurative lymphadenopathy not apparently preceded by a genital ulcer.

Demonstration of microfilariae was decisive in clinching the diagnosis of filariasis which was not considered in the differential diagnosis. Presentation with inguinal lymphadenopathy is a feature common to both LGV and filariasis. The most frequent manifestation of secondary stage of LGV in men is unilateral inguinal lymphadenopathy which does not suppurate in two thirds of cases.¹ Iliac lymphadenopathy often develops in LGV as was observed in our patient.² Painful enlargement of inguinal lymph nodes with fever is the usual presentation in lymphatic filariasis. Lymphangitis can accompany recurrent attacks. Other complications include orchitis, funiculitis, and epididymitis.^{3, 4} These were, however, absent in our patient. It is suggested that lymphatic filariasis should be considered in differential diagnosis of inguinal lymphadenopathy even in areas which are not known to be endemic for it. It is otherwise likely to be missed.