Recurrent steroid-responsive polyserositis of unclear aetiology: a possible post-COVID-19 phenomenon.

A previously healthy male patient presented with relapsing serous effusions affecting the pleural, pericardial and peritoneal membranes, along with thrombocytopaenia, following infection with COVID-19. An extensive workup was performed to rule out potential causes of polyserositis, including an infectious disease screen, autoantibody testing and imaging; however, no clear other cause was found. He exhibited a robust response to high-dose corticosteroid therapy but experienced several recurrences on tapering of treatment. His clinical course and treatment response were most suggestive of an autoimmune or autoinflammatory cause of polyserositis, though without confirmation of a specific underlying diagnosis. This report builds on existing literature on a possible link between COVID-19 and polyserositis.