BI36 A case study of hypereosinophilic syndrome in a patient with atopic dermatitis on dupilumab therapy and <i>Strongyloides</i> infection

Abstract A 33-year-old British Bangladeshi man with a lifelong history of moderate-to-severe atopic dermatitis presented to a dermatology clinic. He had an Eczema Area and Severity Index score of 17.6 and a Dermatology Life Quality Index score of 17. His medical history included asthma, prediabetes and haemorrhoids. Blood tests showed an eosinophil count of 0.7 × 109 cells L−1. He was routinely screened for Strongyloides prior to commencing immunosuppression. His Strongyloides antibody test was positive, with no symptoms of infection, and he was treated with ivermectin. Despite topical treatments and ciclosporin, his eczema persisted, leading to the initiation of dupilumab. Within weeks of commencing dupilumab, he developed fevers, malaise, abdominal pain, diarrhoea, blood in the stool and 6-kg weight loss. Investigations showed a raised faecal immunochemical test (&amp;gt; 200 μg g−1) and faecal calprotectin level (1760 μg g−1), with his eosinophil count increasing to 28.9 × 109 cells L−1, prompting hospitalization. Further evaluations aimed to differentiate between Strongyloides hyperinfection and hypereosinophilic syndrome. Dupilumab was discontinued, and he received four additional doses of ivermectin. Five stool samples tested negative for Strongyloides via polymerase chain reaction (PCR), and all were negative for ova, cysts and parasites. Stool microscopy, culture and sensitivity showed no abnormalities, and no viruses were found on a gastrointestinal virus PCR panel. Colonoscopy revealed left-sided colitis, and biopsy results indicated chronic eosinophilic inflammation with no parasites seen. Genetic tests for haematological malignancy were negative, and a computed tomography scan showed no significant findings. Further investigations to diagnose and assess for end-­organ damage due to hypereosinophilia showed normal serum tryptase, protein electrophoresis, troponin, B-natriuretic peptide, urate, immunoglobulins and echocardiogram results. The diagnosis of hypereosinophilic syndrome secondary to dupilumab, complicated by a prior Strongyloides infection, was confirmed. A tapering course of prednisolone 0.5 mg kg−1 per day led to rapid improvement in his gastrointestinal and systemic symptoms and markedly reducing his eosinophilia. This is a case of hypereosinophilic syndrome with colitis secondary to dupilumab in a patient with positive Strongyloides serology. This case demonstrates the diagnostic difficulty in Strongyloides-positive patients, given that both hypereosinophilic syndrome and Strongyloides hyperinfection can present with colitis, and there is a theoretical risk of disseminated Strongyloides and hyperinfection in patients immunosuppressed with dupilumab.