C5 deficiency in a patient with primary Sjögren's syndrome.

We report a case of C5 deficiency in combination with Sjögren's syndrome (SS). Our patient presented with polyarthritis and complaints of oral and ocular dryness. In the serum there was a very low titer of total hemolytic complement (CH50) due to a deficiency of the fifth complement component. C5 deficiency is often associated with recurrent life threatening infections, membranous glomerulonephritis, and discoid lupus erythematosus, but it has not been described in association with primary SS.