Eosinophilic Pseudoleukemia Due to Toxocariasis in a 3-year-old Patient: Report of A Rare Case

Abstract

Toxocariasis is caused by Toxocara canis and, less frequently, Toxocara catis, intestinal nematodes of dogs and cats, respectively. Humans may become accidental hosts by ingesting embryonated eggs. Clinically, toxocariasis may manifest as visceral larva migrans (VLM), ocular larva migrans (OLM), or covert toxocariasis. This disease typically resolves itself within weeks since the parasites cannot completely mature in the human body and are overcome by the human inflammatory reaction. However, chronic disease is not uncommon due to repeated exposure to infected dogs or cats and long life of the larvae in tissues (months to years). Eosinophilic pseudoleukemia is a very rare condition which may be secondary to chronic Toxocara exposure. We report a 3-yearold previously healthy male with incidentally identified marked leukocytosis (98,100/μL) and eosinophilia (71,000/μL) during routine hemoglobin/iron screen. The patient had no rash and no appreciable hepatosplenomegaly detected by physical examination. Peripheral blood smear showed microcytic hypochromic anemia and marked eosinophilia without left shift, basophilia or circulating blasts. No end organ damage from the eosinophilia was identified, and the patient was asymptomatic from a cardiopulmonary standpoint. Bone marrow biopsy and aspirate showed normocellular marrow, appropriate myeloid and lymphoid maturation with markedly increased but morphologically normal eosinophils (64% of total nucleated cells) and no increased blasts, monocytosis or mastocytosis. Flow cytometry failed to detect any abnormal myeloid or lymphoid populations. Cytogenetics studies and FISH analysis for PDGFRA, PDGFRB, FGFR1, and BCR-ABL rearrangements were normal. The patient had frequent contact with three dogs, and serologic analysis was strongly positive for Toxocara and negative for aspergillus, blastomyces, histoplasmosis, and coccidioides. The diagnosis of toxocariasis with eosinophilic pseudoleukemia was made. The treatment for toxocariasis is albendazole for the patients, as well as elimination of the parasites from infected dogs or cats. His leukocytosis and eosinophilia resolved within 2 weeks of treatment for Toxocara.