An 11-year-old boy presented to the pediatric clinic at Hennepin County Medical Center in Minneapolis, Minnesota with a 2-year history of a limp and pain in the right hip and thigh. Two weeks before this clinical visit, he noted increased pain and swelling in the hip and thigh. Medical history was limited to a history of seizures controlled by antiepileptic medications. On examination, his right thigh had an area of firm induration that was moderately tender to palpation without overlying skin irritation, rash, erythema, or warmth. The absolute peripheral eosinophil count was 966 cells/mm3. Magnetic resonance imaging revealed an anterior thigh fluid collection with a fibrous capsule extending to the joint space. The patient underwent fluoroscopic aspiration of the right hip but a minimal amount of fluid was obtained. The patient was then taken to the operating room for tissue sampling, irrigation, and debridement of the right hip and thigh.
Intraoperative samples showed granulation tissue and a foreign body reaction containing a filarial nematode (Fig. 1).
What is your diagnosis?
Diagnosis: The intraoperative samples taken from the boy's thigh showed granulation tissue and a foreign body reaction containing Onchocera organisms.
The patient was treated successfully with ivermectin. An ophthalmologic examination showed no intraocular involvement. The patient's surgical wound took months to heal secondary to superimposed bacterial infection.
Approximately 18 million people worldwide are infected with Onchocerca volvulus. The most common clinical manifestations are skin and ocular disease due to microfilariae, but those infected with O. volvolus have a wide variety of clinical presentations, including growth retardation and epileptic seizures.4 The boy in our case did have a history of seizures and a markedly abnormal electroencephalogram; however, his brain magnetic resonance imaging scan was normal.
Onchocerciasis causes significant morbidity from skin involvement with manifestations that include acute and chronic papular dermatitis, subcutaneous nodules, hanging groins, depigmentation, and lichenification of the skin.3 Skin lesions caused by onchocerciasis were historically seen as a consequence of poverty and poor personal hygiene and were even mistaken for leprosy.3 The social discrimination could have contributed to the decreased public health efforts toward management of these disabling skin manifestations.
Infected individuals are initially asymptomatic. The adult worms live in fibrous subcutaneous nodules formed by scar tissue called onchocercomas. The nodules allow the nematode to evade the host's immune system, and are typically 3 to 5 cm in diameter and contain 2 or 3 female and 1 or 2 male adults. Nodules are often located over bony prominences. Deep-seated onchocercomas are less common and can be more difficult to detect. Substances produced by the adult worms inhibit the normal immune response from the host.1 The nodules contain macrophages and fibrous proteins that surround the adult worm; eosinophils and lymphocytes are predominately at the periphery of the nodule.1 Symptomatic disease can usually be attributed to the movement of millions of microfilariae through subcutaneous and ocular tissues causing local host inflammatory responses. Identification of onchocercomas is essential to treating this condition. In our case, symptoms of hip and thigh pain were caused by tissue compression from adult worms in a large fibrous nodule in the thigh (Figs. 1-3).
The diagnosis of onchocerciasis is traditionally made by taking skin snips from the iliac crest, immersing them in saline, and then counting the microfilariae under the microscope.1 Skin lesions may occur in the absence of detectable microfilariae by the skin-snip method.7 Ocular disease is typically diagnosed by using slit-lamp examination. Clinicians must rely on history and demographic information for accurate diagnosis. Polymerase chain reaction is highly sensitive but is not yet available for general use. The diagnosis of onchocerciasis may be delayed in nonendemic areas. This case illustrates the importance of obtaining a clinical history that includes information about the patient's country of origin and/or residence and an understanding that some organisms can persist within the host for many years. Although eosinophilia is a helpful clue in the diagnosis of parasitic infections, up to 30% of cases of onchocerciasis will have a normal eosinophil count. Elevated blood eosinophil counts are more prevalent in those with skin manifestations.7 With the increasing numbers of immigrants from Africa to the United States and Western Europe, health care workers should become more familiar with onchocerciasis and other nonendemic parasitic infections. In persons from endemic areas, the diagnosis of onchocerciasis should be considered in those with eosinophilia and skin itching with or without a rash or ocular symptoms.
The authors thank Charles Cartwright, PhD, for (Figure 1.
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