ABSTRACT
Systemic capillary leak syndrome (SCLS), also known as Clarkson's disease, is a rare disorder of unknown aetiology. Since SCLS was first described in 1960, fewer than 500 cases have been reported. SCLS is diagnosed by the classic triad of hypotension, haemoconcentration and hypoalbuminaemia resulting from fluid extravasation. Some reports show that SCLS may sometimes occur as a side effect of adenoviral vector COVID-19 vaccines, although there is only one report (two cases) of SCLS after receiving a messenger RNA vaccine. Survival rates for SCLS are very poor without treatment, so it is crucial for clinicians to recognise this disorder. A middle-aged woman who presented with generalised malaise and anasarca after receiving the BNT162b2 COVID-19 vaccine was diagnosed with SCLS. Treatment with methylprednisolone and intravenous immunoglobulin was commenced and her symptoms resolved. We expect that this case report will add to the existing literature on this rare disorder and the side effects of vaccinations.