A case of chronic, corticosteroid-responsive arthritis affecting particularly one ankle in a patient with type IV hyperlipoproteinaemia is reported. After gout or inflammatory rheumatism of another nature had been excluded, and following synovial fluid examination and synovial membrane biopsy, a diagnosis of type IV hyperlipoproteinaemia rheumatism was made. At electron microscopy, the synovial membrane showed numerous large spumous cells and a peculiar appearance of the capillary vessels.