In July, 2005, a 28-year-old white man was referred to our unit with a 3-month history of recurrent painful asymmetrical swelling and induration of the limbs (fi gure, A). His history was otherwise unremarkable. On physical examination, the skin was too taut to pinch. The rest of the examination was normal, and there was no pruritus. 8 months previously he had spent 6 weeks travelling in several African countries. Blood test results showed hypereosinophilia (4·69×10/L). Liver function tests were normal, and C-reactive protein was below 8 mg/L. Rheumatoid factor was negative, and total complement, C3 and C4 concentrations, and anti-DNA antibody titres were normal. Stool examination for ova and larvae was negative. No microfi lariae were detected in peripheral blood. The serum antifi larial titre was 1 in 200 by direct immunofl uorescence (normal: less than 1 in 200), and electrosyneresis was negative. Serological tests for schistosoma, toxocara, distomatosis, and trichina were negative. Hepatic ultrasonography was normal. MRI of the aff ected limb showed increased signal intensity within the superfi cial and deep fascia (fi gure, B). We made a presumptive diagnosis of onchocerciasis with limb swelling, and treated our patient with ivermectin (8 mg), after which the swelling rapidly subsided. Two further doses were followed by the disappearance of hypereosinophilia after 6 months of follow-up. Tests for antifi larial antibodies by direct immunofl uorescence became positive (1 in 800) after 4 weeks, and one arc appeared on electrosyneresis. When last seen, in May, 2006, the patient had no further symptoms. Onchocerciasis is a fi larial disease caused by the nematode Onchocerca volvulus. It is transmitted by small blackfl ies of the genus Simulium, which breed in fastfl owing water. The infection is endemic throughout tropical Africa, parts of central and south America, and parts of the Arabian peninsula. Onchocerciasis can be acquired during short visits to highly endemic foci, especially in forested areas. The incubation period ranges from 5 to 20 months. The typical clinical signs of onchocerciasis in endemic populations include intense pruritus, subcutaneous nodules, papular dermatitis, and disfi guring depigmentation (leopard skin). Onchocerciasis is a common cause of visual impairment (river blindness). Peripheral eosinophilia is present in all cases. The diagnosis is based on clinical fi ndings. Diff erent clinical manifestations have been observed in expatriates and travellers, in whom onchocerciasis rarely leads to irreversible skin or eye damage. The infection may remain asymptomatic or lead to a simple erythematous rash, with maculopapular lesions on the trunk or legs and, in some cases, pruritus. Travellers returning from endemic areas with onchocerciasis may present with signs of eosinophilic fasciitis, which is characterised by swelling of the limbs, severe eosinophilia, and fascia infi ltration. Although limb swelling is uncommon, French authors fi rst coined the terms “equatorial arm” and “gros bras camerounais” (Cameroonian big arm). The diagnosis of onchocer chiasis is diffi cult in mildly or recently infected individuals. Microfi lariae are few in number and tend not to be present in peripheral blood. In addition, serological tests have poor sensitivity. In one study, the specifi c skin snips test was positive in only 53% of 31 reported cases. Negative parasitological and serological tests for O volvulus contribute little to the diff erential diagnosis. The presence of recurrent limb swelling and eosinophilia, combined with a history of travel to endemic areas, should alert the clinician to the possibility of onchocerciasis. Ivermectin is eff ective in onchocerciasis but is best combined with doxycycline to avoid possible recolonisation of the skin once the adult worms resume production of micro fi lariae.
Read full abstract
Aug 15, 2012
Gaurav Solanki 
Open Access
