Strongyloides stercoralis Eggs in a Urethral Smear after Bone Marrow Transplantation

SIR—We read with interest the article by Siddiqui and Berk [1] that comprehensively described the diagnosis of Strongyloides stercoralis infection. Strongyloidiasis seems to increasingly affect a high-risk group of persons who have disturbed cellular immunity, including persons with hematologic malignancies [2]. We describe the unusual finding of S. stercoralis eggs on a urethral smear, which sheds new light on the diagnosis of S. stercoralis infection in immunosuppressed patients.

Philadelphia chromosome—positive chronic myeloid leukemia was diagnosed 6 years ago in a 38-year-old male truck driver whose regular trucking route was between northern and southern Europe. Recently, he underwent allogeneic blood stem cell transplantation after receiving conditioning therapy with busulfan and cyclophosphamide. The peripheral blood eosinophil count was normal before transplantation. Macrohematuria and severe suprapubic pain occurred after the second cyclophosphamide application on day 2 before transplantation. The differential diagnoses included acute cyclophosphamide toxicity, nephrolithiasis, urological malignancy, thrombocytopenia-induced bleeding, and urogenital infection. The results of routine testing for infection due to bacteria, mycobacteria, cytomegalovirus, and adenoviruses were negative. Marrow engraftment was noted (leukocyte count, 1000 leukocytes/µL) on day 16 after bone marrow transplantation, with 2% eosinophils. On the same day, a urethral smear was sent to the parasitology laboratory to exclude trichomoniasis and other protozoan and helminthic infections. Unexpectedly, S. stercoralis eggs harboring motile larvae were found during high-power field microscopic evaluation of the smear.

After the patient received anthelminthic treatment with mebendazole (300 mg b.i.d. for 3 days), the eosinophil count became undetectable and the macrohematuria improved. After another 12 days, the peripheral blood eosinophil differential increased to 23% and macrohematuria recurred. When albendazole therapy (2 courses of 400 mg b.i.d. for 7 days each) was introduced, the eosinophil count decreased and then remained at a normal level. However, the macrohematuria did not improve. Three months after albendazole therapy was completed, disseminated cytomegalovirus infection developed, followed by graft-versus-host disease and adenovirus infection of the urinary bladder; unfortunately, the patient died on day 167 after transplantation.

S. stercoralis, either in adult or egg form, has never before been reported outside of the gastrointestinal tract or sputum [3]. Adult worms deposit the eggs into the intestinal mucosa, where the larvae hatch immediately after deposition. Larval migration usually affects the gastrointestinal tract and, temporarily, the pulmonary tract [4]. Highly invasive dissemination into extraintestinal sites has been associated with immunodeficiency and hyperinfection [1]. Although immunosuppression that occurs after chemotherapy supports S. stercoralis dissemination [5], high-dose chemotherapy might affect the larvae [6] and, as happened in the patient we describe, possibly inhibit the hatching process. The presence of S. stercoralis eggs with motile larvae in the urethral smear suggests that the eggs might have migrated from the gastrointestinal tract to the urinary tract or that an adult female might have invaded the urinary tract.

As pointed out in Siddiqui and Berk's review [1], screening for latent S. stercoralis infection might be a valuable option for patients with a relevant geographic history before they undergo chemotherapy, bone marrow transplantation, or stem cell transplantation. The finding of S. stercoralis eggs should be considered in the diagnostic workup of persisting hematuria that occurs after stem cell transplantation.