Strongyloidiasis

A 58-year-old man with type 2 diabetes mellitus and hypertension was hospitalized with acute diarrhea characterized by several brown, liquid depositions per day. He also complained of lower abdominal pain and bloating and a 10-lb weight loss in the past 2 months. He denied fever or chills, use of corticosteroids, and travel outside the United States. Lucía C. Fry, MD, and Klaus E. Mönkemüller, MD, of Scottsdale, Ariz, noted orthostatic and bilateral lower abdominal tenderness on deep palpation and no rebound. His hemoglobin level was 11.5 g/dL (which indicated mild anemia); glucose, 229 mg/dL (normal, 70 to 105 mg/dL); and albumin, 3.5 g/dL (normal, 3.4 to 4.5 g/dL). The white blood cell count was 10,400/μL, with 22% eosinophils. Stool examination was negative for ova and parasites. Colonoscopy revealed multiple yellow-pigmented, xanthomalike lesions throughout the colon (A).

Histopathologic examination of a specimen from these lesions showed focal, diffuse eosinophilic infiltration and Strongyloides larvae (B). Strongyloidiasis, caused by the nematode Strongyloides stercoralis, is endemic in tropical areas of Africa (where up to 21% of the population are infected), Asia, and Latin America, as well as in the southeastern United States (where 2.5% are infected). Once the parasite enters the skin from fecal-contaminated soil, it migrates through the venous circulation to the lungs and penetrates the alveoli. The parasite is then expectorated or expelled from the bronchi or trachea and swallowed. Adult forms of S stercoralis reside in the surface of the duodenum or jejunum and release ova in the lumen, where the ova become rhabditiform larvae. They develop into filariform larvae, which are able to penetrate intestinal mucosa or perianal skin (autoinfection). The cycle is then completed via the venous circulation. In contrast to other nematodes— which transform into infective filariform larvae outside the host—S stercoralis is the only helminth capable of completing the cycle within the host. Therefore, autoinfection may persist for decades. The symptoms of strongyloidiasis are abdominal pain, diarrhea, vomiting and, in cases of extensive infection, malabsorption, steatorrhea, and weight loss. Strongyloidiasis can affect both immunocompetent as well as immunocompromised persons (such as those with a history of malignancy, organ transplantation, diabetes mellitus, or corticosteroid use).

However, in immunocompromised patients, Strongyloides infection can lead to hyperinfection syndrome with multisystemic disease, which can be life-threatening. Diagnostic accuracy by stool examination is no higher than 46%. The most accurate diagnostic method is duodenal aspiration or endoscopic biopsy. Laboratory data are usually not relevant; however, eosinophilia is frequently present in immunocompetent persons. For uncomplicated infections, ivermectin is recommended by the CDC. For disseminated infection or hyperinfection in immunocompromised patients, thiabendazole is recommended. This patient was treated with thiabendazole for 2 days. His symptoms gradually resolved over a week.