Familial discoid lupus erythematosus associated with heterozygote C2 deficiency

Area of Science:

• Immunogenetics
• Rheumatology
• Complement System Biology

Background:

• Chronic discoid lupus erythematosus (CDLE) is an autoimmune condition.
• Complement component C2 deficiency is a rare genetic disorder.
• Genetic associations with human leukocyte antigen (HLA) markers are common in autoimmune diseases.

Purpose of the Study:

• To investigate the genetic basis of C2 deficiency in a family with CDLE.
• To determine the association between C2 deficiency and specific HLA and Factor B (Bf) alleles.
• To analyze the linkage between the C2 deficiency gene and HLA and Bf genes.

Main Methods:

• Family-based genetic analysis.
• HLA and Bf typing.
• Linkage analysis using polymorphic markers.

Main Results:

• Heterozygous C2 deficiency identified in siblings with CDLE and other family members.
• Significant association found between C2 deficiency and HLA-B18 and HLA-Dw2 alleles.
• The slow allotype of Factor B (BfS) was present in affected individuals.
• Linkage studies indicated close proximity between the C2 deficiency gene and genes for B18, Dw2, and BfS.
• One recombinant event suggested tighter linkage between HLA-D and Bf than between HLA-B and Bf.

Conclusions:

• C2 deficiency is genetically linked to specific HLA and Bf alleles in this family with CDLE.
• These findings contribute to understanding the immunogenetic basis of lupus erythematosus.
• The study highlights the importance of complement system genetics in autoimmune disease susceptibility.