Infliximab Attenuates Paediatric Inflammatory Multisystem Syndrome in SARS-CoV-2 (PIMS-TS)

Paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) is a newly described condition. It has a spectrum of presentations related to hyperinflammation and cytokine storm. We report the first case of PIMS-TS in a child on established anti-Tumor Necrosis Factor-alpha (anti-TNF-α) therapy; a 10 year-old girl with ulcerative colitis treated with infliximab. The patient had 6-weeks of daily fever with mucocutaneous, gastrointestinal, renal and hematologic involvement. Biomarkers of hyperinflammation were present including: hyperferritinaemia (up to 691 µ/L; normal 15-80 µg/L), C-reactive protein (CRP) (>100mg/L for >10 days, normal 0-5 mg/L), erythrocyte sedimentation rate (ESR) consistently >100mm/hr (normal 0-15 mm/hr), raised white cell count with neutrophilia, elevated D-dimer and lactate dehydrogenase (LDH), anaemia and Mott cells on bone marrow analysis. Extensive investigations for alternative diagnoses for pyrexia of unknown origin (PUO) were negative. The condition was refractory to treatment with intravenous immunoglobulin (IVIG) but improved within 24hrs of high dose methylprednisolone. Infliximab treatment followed and the patient has remained well at follow up. Polymerase chain reaction (PCR) and serology for SARS-CoV-2 were negative. Current series report such negative findings in up to half of cases. The patient experienced a milder clinical phenotype without cardiac involvement, shock or organ failure. It is postulated that prior anti-TNF-α therapy attenuated the disease course. Infliximab therapy may interfere with serology testing and produce false negative results. This case supports the need for investigation into infliximab as primary therapy for PIMS-TS.