We report on a case of systemic capillary leak syndrome associated with a monoclonal band on plasma electrophoresis. In our patient hospital admission was precipitated by ischaemic pain in the left lower limb, associated with polycythaemia, renal failure and hypovolaemic shock. Fluid resuscitation, venesection and renal replacement therapy were instituted but a compartment syndrome developed necessitating surgery. Failure of tracheal intubation resulted in the requirement for a surgical airway. Despite surgical and resuscitative efforts the outcome was fatal from hypovolaemia and hyperkalaemia. We aim to highlight the difficulties in managing this condition and to remind healthcare workers to include it in the differential diagnoses for patients presenting with polycythaemia; in particular polycythaemic patients with a monoclonal band on plasma electrophoresis.