INCOMPLETE FUNCTIONAL DEFICIENCIES OF THE 4TH (C4) AND 2ND (C2) COMPONENTS OF COMPLEMENT IN A PATIENT WITH LINEAR FRONTOPARIETAL SCLERODERMA AND HIS FAMILY - DEFICIENCIES DETERMINED BY A GENE NOT LINKED TO HUMAN-LEUKOCYTE ANTIGEN SYSTEM

Background: In a previous study, a patient suffering from linear front oparietal scleroderma and some of his family members were found to hav e an incomplete functional deficiency of the second component (C2) of complement (C). In this study, the proband and the rest of his family members were investigated for functional deficiencies of C2 and the fo urth component of C (C4). A search for null alleles of C2 (C2Q0) and C4 (C4Q0) was made to find out whether their occurrence is responsibl e for incomplete Functional deficiencies. HLA analysis was performed t o find out whether deficiencies are linked to HLA alleles known to be associated with C4Q0 and C2*Q0. Possible large deletions at C4 and 21 -hydroxylase (21-OH) gene loci were also investigated In some family m embers. Observations: The proband had a combined functional deficiency of C4 and C2. Some of his family members had a partial functional def iciency of C4, some of C2 and some of C4 and C2, none had null allies of C2 (C2Q0), factor B (B*Q0) or C4B (C4B*Q0). C4*Q0 or functional C4 deficiency in this family was not associated with HLA-A1;B8;DR3 allel es. C2 deficiency was also not associated with HLA antigens known to b e associated with. type I and II C2 deficiencies. No gene deletion or unusual polymorphism at C4A and 21-OHA loci could be seen by restricti on fragment length polymorphism(RFLP) studies. Conclusions: Combined a nd isolated partial functional deficiencies of C4 and C2 observed in t he proband and many of his family members were not caused by C activat ion or null alleles. They were not linked to HLA system and were remin iscent of those observed previously in a family in which C4 deficiency was determined by a gene not linked to the HLA system.