Subcutaneous nodules as a manifestation of onchocerciasis. A rare condition in the United States.

Although infection with tissue nematodes is a significant health problem in many parts of the world, such cases are unusual in the continental United States. This report describes a case of Onchocerca volvulus infection, acquired by a 38-year-old female missionary in northern Brazil, that manifested as subcutaneous nodules in the groin and flank two years after the patient's return to the United States. A year previously, a wrong diagnosis of Wuchereria bancrofti was made at biopsy. At that time, treatment with diethylcarbamazine citrate had to be discontinued because of intense pruritus. Examination of a wet saline impression smear of a new biopsy specimen showed the adult worms to have regularly arranged outer annular ridges, which, together with the pruritus after treatment with diethylcarbamazine (a positive Mazzotti test), led to the diagnosis of onchocerciasis. Retreatment with diethylcarbamazine again caused pruritus, but this was tolerated as were subsequent treatments.