An unusual rash: Strongyloides stercoralis presenting as larva currens in a 12‐year‐old girl with Crohn's disease

A 12-year-old non-Indigenous girl from a regional community in Central Australia presented with several months of increased tiredness, pharyngitis, poor appetite and abdominal discomfort. She had a history of Crohn’s disease diagnosed 4 years earlier and managed with bimonthly infliximab infusions. She also had a history of iron deficiency, eczema managed with topical steroids and nut allergy. She had received several courses of oral antibiotics for pharyngitis from her general practitioner, without improvement. She had no history of vomiting, altered bowel habit, fever, camping or overseas travel, and her immediate family and pet dogs were well. On examination, she had mild abdominal tenderness and angular chelitis. She was noted to have a linear, pruritic maculopapular rash that extended from the left lateral malleolus to the posterior aspect of her calf and along her posteromedial thigh (Figs 1-3). The rash had first appeared several weeks before on her ankle and calf and had advanced proximally over the next week. The patient had not had any rashes elsewhere and had no history of generalised pruritus or urticaria. Investigations demonstrated a normal full blood examination, including a normal eosinophil count of 0.3 × 10/L and normal erythrocyte sedimentation rate and C-reactive protein. Her ferritin decreased to 16 μg/L. No acute stool sample was collected, but six previous samples cultured and examined for ova, cysts and parasites were normal. Strongyloides stercoralis serology was performed using an IgG enzyme-linked immunosorbent assay (ELISA) using the soluble fraction of filariform S. stercoralis larvae. The patient’s ELISA result was elevated, with an optical density of 0.44 units (normal range ≤0.2 units). In light of her immune compromise, the patient was treated with weekly oral ivermectin until her symptoms resolved. Repeat serology 3 months after treatment was initiated was <0.2. Her younger sibling was also receiving infliximab infusions for Crohn’s disease and was treated for positive S. stercoralis serology. Household contacts and pet dogs were treated with a standard course of oral ivermectin, receiving two doses 1 week apart.