C1q deficiency: identification of a novel missense mutation and treatment with fresh frozen plasma.

A Turkish patient with C1q deficiency presented with a lupus-like disease, and a new missense mutation at A chain is presented. To characterize the genetic defect, all exons of the genes for the A, B, and C chains of C1q were sequenced in the patient. This revealed a missense mutation in the collagen-like domain of the A chain, p.Gly31 Arg. No other sequence variants, including the common silent mutations, were found in the three chains. Exon 1 of the C1q A chain was sequenced in 105 samples from healthy controls for this particular mutation. None of these carried the mutation. The C1q-deficient patient was treated with fresh frozen plasma infusions. Our findings showed that Turkish patients may have different mutations than the previously described common mutation, and once again, not only nonsense mutations but also missense mutations cause hereditary C1q deficiency. Regular fresh frozen plasma infusions to the patient have been clinically and therapeutically successful.