Clinical presentation of human C1q deficiency: How much of a lupus?

Hereditary human C1q deficiency has been well described to be associated with high susceptibility for the development of systemic lupus erythematosus (SLE). The majority of subjects present a clinical syndrome closely related to SLE. However, limited information is available about the primary diagnosis and particular clinical manifestations of SLE in this specific subgroup of patients. In this review, we performed a comprehensive search of electronic databases up to November 2014 to identify and analyze reports on patients with C1q deficiency. We identified 71 C1q-deficient patients descending from 45 families that had been published. According to the American College of Rheumatology (ACR) diagnostic criteria for SLE 39/71 (55%) subjects could be classified as having SLE. Another 16/71 (22.5%) presented a SLE-like syndrome (defined as 3 positive ACR criteria) whereas in 16/71 (22.5%) no SLE could be diagnosed at time of publication. Symptoms began at a median age of 5 years, male and females being equally affected. Discoid rash (56% versus 10%, p<0.001) and oral ulcers (49% versus 24%, p<0.001) occurred significantly more frequent in C1q deficiency-associated SLE/SLE-like disease than in sporadic SLE, whereas arthritis (38% versus 84%, p<001) and anti-ds-DNA (18% versus 78%, p<0.001) occurred less frequently. Renal and neurological manifestations were found to occur similarly frequent. The severe course of disease in some patients seemed to be mostly due to severe infections at early ages and not in particular due to more aggressive SLE manifestations.