PD011 - SUBCUTANEOUS DIROFILARIASIS IN A GIRL WITH RHEUMATOID ARTHRITIS (ID 1176)
Abstract
Title of Case:
SUBCUTANEOUS DIROFILARIASIS IN A GIRL WITH RHEUMATOID ARTHRITIS
Background:
Human subcutaneous dirofilariasis is a rare helminthic infection, caused by filarial worms Dirofilaria species
Case Presentation Summary:
A 9-year-old girl with a history of juvenile rheumatoid arthritis with enthesitis treated with adalimumab presented with a subcutaneous nodule on the forehead with a 2-month duration.The nodule was non-tender and mobile with a 1.5 cm in diameter.The systemic examination was unremarkable.Magnetic Resonance Imaging (MRI) brain scan was normal. Further laboratory findings showed normal blood counts, normal IgE, and no eosinophilia. Clinical differential diagnosis is very broad and includes rheumatoid nodule, dermoid cyst, lipoma, hemangioma, lymphangioma, osteoma, epithelioid sarcoma, infectious granuloma, and deep granuloma annulare. Excision of the subcutaneous lesion was decided upon the clinical implication of a malignant tumor.Histology showed a nodule with a mixed inflammatory response involving lymphocytes and eosinophils around the lesion’s centre, with fragments of a Dirofilaria repens female worm. Under the microscope, cross sections of the female worm are depicted.The worm is covered by a thick multilayered cuticle with longitudinal ridges on the outer surface. This is the main feature that differentiates this parasite from adult Onchocerca worm.The adult female’s uteri contain only ova, as the worm does not reach maturity in humans and microfilaria are not produced. On the basis of microscopic and pathology examination, worm was thus identified as Dirofilaria repens. Excision of the subcutaneous lesion is both diagnostic and therapeutic.
Learning Points/Discussion:
This case emphasizes that human subcutaneous dirofilariasis should be considered in the differential diagnosis of a single subcutaneous nodule, especially, when the patient is coming from an endemic area. The clinical implication of human dirofilariasis is that, this subcutaneous lesion may be initially misidentified before the correct diagnosis is made.
