Hereditary C2 deficiency: association with skin lesions resembling the discoid lesion of systemic lupus erythematosus.

Two patients with hereditary homozygous C2 deficiency are described. They showed many similar clinical features. Both had discoid-like skin rashes and serologic abnormalities consistent with SLE, but neither had evidence of involvement of any organ other than skin. Although biopsy of these lesions revealed expected changes by light microscopy, typical immunofluorescent findings were not present. The presence of the HL-A haplotype 10, W18 was seen in both families and was associated with the C2 deficiency gene. The 2 patients were mutually nonreactive in MLC tests and both were found to be homozygous for the LD7a type.