Acquired C1q deficiency caused by monoclonal paraproteinaemia

Acquired C1q deficiency secondary to anti C1q auto-antibodies may result in the hypocomplementaemic urticarial vasculitis syndrome and may also be seen in active systemic lupus erythematosus. Some patients with acquired C1 inhibitor deficiency are found to have an underlying malignancy, most commonly lymphoma. We report a case of a 40-year-old man presenting with a lupus-like illness with acquired C1q deficiency secondary to a monoclonal paraprotein in the presence of splenic lymphoma with villous lymphocytes. His clinical symptoms correlated with the presence of the paraprotein. Relapse coincided with a rise in the paraprotein and fall in C1q, C3 and C4. There was no improvement in his clinical condition following combination chemotherapy. He remains on oral prednisolone.