Strongyloides stercoralis hyperinfection in a patient with acute lymphoblastic leukemia.

Strongyloides stercoralis is an intestinal nematode.[12] Strongyloides infection is endemic in tropical, subtropical and sporadic in temperate areas.[3] Strongyloides larvae are identified in feces, body fluids, or in biopsy of involved tissues. It has a wide spectrum of manifestations varying from asymptomatic eosinophilia in the immunocompetent host to disseminated disease with septic shock in immunocompromised host.[12]

In immunocompromised condition, the auto-infective cycle of Strongyloides can become amplified into a potentially fatal hyperinfection syndrome. Hyperinfection syndrome is characterized by increased numbers of infective filariform larvae in stool and sputum and clinical manifestations of the increased parasite burden and migration, like gastrointestinal bleeding and respiratory distress.[4]

An 18-years-old male was diagnosed with T-cell acute lymphoblastic leukemia (ALL) and attained remission after induction chemotherapy. He presented after the reinduction phase of chemotherapy, comprising of daily doses of oral dexamethasone 14 mg, with pain in the abdomen, vomiting, and bloating sensation. Initially, it was thought to be steroid-induced gastritis. He did not show any improvement with antacids or proton pump inhibitor. A peripheral blood smear examination revealed eosinophilia with 16% eosinophils. Absolute eosinophil count was 900/µl. Stool microscopy showed larvae of S. stercoralis. An upper gastrointestinal endoscopy showed grossly edematous and erythematous duodenal and jejunal mucosa studded with tiny pearly whitish nodules [Figure 1a and b]. Duodenal biopsy revealed larval forms and eggs of S. stercoralis within the crypts [Figure 1c]. A combination of oral ivermectin 12 mg on days 1,2,15 and 16 along with albendazole 400 mg twice daily for 2 weeks was given following which the patient had prompt resolution of his symptoms. Seven days after starting treatment the stool microscopy did not show any larvae.

Figure 1

(a) Upper GI endoscopy showing duodenal mucosa studded with whitish pearly nodules due to parasitic infection (black arrow); (b) upper GI endoscopy showing duodenal mucosa with areas of mucosal hemorrhage (white arrow); (c) histopathology showing characteristic Strongyloides eggs and larvae within the crypts (black arrows). Also seen is an intense lymphoplasmacytic infiltrate (blue arrow) (hematoxylin and eosin ×400)

Autoinfection and hyperinfection with S. stercoralis is more common in immunocompromised hosts. Usually, these patients present with non-specific abdominal symptoms.[13] Hyperinfection syndrome results from an increase in the concentration of circulating Strongyloides filariform larvae. Immunodeficiency states like hypogammaglobulinemia, acquired immunodeficiency syndrome, Cushing syndrome and patients receiving anti-cancer chemotherapy and corticosteroids can cause fatal hyperinfection.[2] Chemotherapy is supposed to play a role in promoting the maturation of Strongyloides larvae from a quiescent rhabditiform stage. Hyperinfection can lead to organ invasion due to large increase in worm burden.[3] A high degree of suspicion and necessary investigations can rule out strongyloidiasis in ALL patients with unexplained abdominal symptoms especially after induction and reinduction phases due to prolonged steroid exposure.[1]

A study by the University of Texas M. D. Anderson Cancer Center had opined that strongyloidiasis was uncommon in patients with cancer. It tends to remain localized in patients with solid-organ malignancies.[4] Very few reports are available in the literature regarding Strongyloides infection in leukemia patients.[34] However, a study from Malaysia provided evidence of the occurrence of S. stercoralis infection among cancer patients.[5]

Strongyloides stercoralis hyperinfection may have been the unidentified cause of death in oncology centers in tropical regions in the absence of proper investigations. Successful management of hyperinfection syndrome requires early detection and initiation of therapy.[1] Ivermectin is the most effective therapy in strongyloidiasis.[6] In a randomized study, four doses of Ivermectin (on days 1, 2, 15, and 16) were no more efficacious than a single dose in non-disseminated strongyloidiasis. For hyperinfection and disseminated strongyloidiasis; especially in the immunocompromised; the higher dose schedule may be preferred in the absence of definite data.[7] Therefore, it is essential for cancer patients who are at risk for disseminated strongyloidiasis to have accurate diagnosis and appropriate treatment before and during immunosuppressive therapy.[45]

Strongyloidiasis in acute leukemia is a mimicker in that the signs and symptoms are non-specific. High degree of suspicion and prompt treatment avoids unnecessary morbidity and delay in chemotherapy.

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