To the Editor:
Cutaneous filariasis is a group of infectious diseases caused by more than 60 different nematode species and endemic to approximately 83 countries.1,2 These infections are transmitted to humans by vectors such as mosquitoes, blackflies, biting midges, or Tabanid flies.1 The blood meal taken by vectors allow microfilariae to enter the skin and develop into adult worms.1-3 It is postulated that filarial infections were first described in 2000 bc by Egyptian statues demonstrating elephantiasis, or swollen limbs, caused by chronic infections.1 Although there are numerous filarial nematode species that infect humans, each life cycle is similar. First, the arthropod vector transmits infective larvae through human skin during a blood meal. Then larvae migrate to host body parts where they mature into adults. Infective filariae require 1 to 2 weeks to form; arthropods may then have another blood meal and transmit the infection to another host.1
Filarial parasites have been categorized into groups based on the site of adult worm stage habitat. The cutaneous group includes Loa loa, Onchocerca volvulus, Mansonella perstans, and Dipetalonema streptocerca. The lymphatic group includes Wuchereria bancrofti, Brugia malayi, and Brugia timori. Lastly, the body cavity group includes Mansonella ozzardi. Because humidity is required for survival of the infective larval stage, individuals from tropical countries in Africa, Central America, and South America most commonly are affected.1 These diseases also are related to poor housing quality and inadequate sanitation.1,3,4 Travel for business, medical missions, pleasure, or emigration has caused increased filarial infections globally. In fact, dermatologic disorders with infectious etiologies cause approximately 17% of travelers to seek medical attention.3
Dermatologic manifestations indicative of a potential cutaneous filarial infection include papules, nodules, excoriations with secondary xerosis, lichenification, skin pigment changes, and/or severe pruritus. However, individuals from filarial endemic regions may not demonstrate any clinical signs or symptoms, despite having microfilariae in their blood,1 which enables the disease to propagate and poses a major public health concern. In fact, patients with chronic filarial infections are at increased risk for developing lymphedema, elephantiasis, or blindness, which are hypothesized to be the second largest cause of permanent disability worldwide.1 Although rarely seen in US citizens, cutaneous filariasis should always be a diagnostic consideration in patients who present with a pruritic eruption and have a travel history to tropical countries. We report a case of cutaneous onchocerciasis in a US citizen who developed a pruritic eczematous eruption on the right upper arm following an arthropod assault while working in an Onchocerca endemic region approximately 1.5 years prior.
A 33-year-old woman presented to our outpatient dermatology clinic with the chief concern of a pruritic rash on the right arm (Figure 1). She revealed a history of travel to Peru, associated symptoms, prior diagnoses, and attempted treatment regimens. Over a 1.5-year period, the patient traveled for work-related reasons to Madre de Dios, Peru. During that time, the patient experienced 2 bouts of severe abdominal pain, nausea, and vomiting that she attributed to poor food and water quality. She did not immediately seek medical attention. She also developed skin manifestations that began as a pruritic and irritating pinpoint-sized red papule on the right eyelid, possibly a site of an arthropod assault. She then experienced episodic eyelash loss (Figure 2) and subsequent vision changes, including blurry vision, halos around lights, and dimming around the periphery. When the patient developed circular, pink, pruritic plaques on the right upper extremity, she sought medical attention in Lima, Peru. She was diagnosed with tinea corporis and prescribed an oral antibiotic and topical antifungal.
Figure 1. A, Erythematous patches on the right arm. B, A 1-cm subcutaneous nodule on the right elbow with overlying skin discoloration.
Figure 2. Clinically apparent eyelash loss.
This treatment regimen did not result in improvement. In the following months, the patient noticed worsening of the ocular symptoms, and she developed a dry cough with occasional dyspnea. She again sought medical attention in Peru and was referred to an ophthalmologist who suspected Demodex mite or fungal infection; however, workup for those pathologies was negative. The respiratory symptoms continued to worsen, particularly at night, and she began to experience palpitations.
Upon returning to the United States, the patient was evaluated by her primary care physician who ordered the following laboratory tests: a complete blood cell count with differential, comprehensive metabolic panel, vitamin D level, blood culture, lipid panel, ferritin level, and thyroid function. An electrocardiogram, throat culture, and stool culture for ova and parasites also were obtained. The electrocardiogram showed sinus tachycardia, and the stool culture revealed blastocystis, for which she was prescribed oral metronidazole and tinidazole. The other results were within reference range, and the throat culture showed normal oropharyngeal microbes.