Paediatric Inflammatory Multisystem Syndrome Temporally Associated With SARS-CoV-2 [PIMS-TS] in a Patient Receiving Infliximab Therapy for Inflammatory Bowel Disease.

Paediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 [PIMS-TS] is a newly described condition. It has a spectrum of presentations proposed to occur as part of a post-infectious immune response. We report the first case of PIMS-TS in a child on established anti-tumour necrosis factor alpha [anti-TNFα] 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 haematological 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/h [normal 0-15 mm/h], 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 24 h 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. Accepting the wide spectrum of PIMS-TS presentations, it is possible that previous anti-TNFα therapy may have attenuated the disease course. Given the uncertainty around therapeutic strategies for PIMS-TS, this case supports the need for further investigation into continuing infliximab as a treatment option for the condition.