OCULAR CICATRICIAL PEMPHIGOID - A CASE-REPORT OF MONOZYGOTIC TWINS DISCORDANT FOR THE DISEASE

Objective: To identify the major histocompatibility complex markers an d the autoantibody associated with ocular cicatricial pemphigoid (OCP) in a proband, her unaffected cotwin, and the children of the cotwin. Ocular cicatricial pemphigoid is a chronic autoimmune disorder that af fects the conjunctiva and other squamous epithelium. It is associated with the major histocompatibility complex class II alleles that are pr esumed to provide enhanced susceptibility to the disease. We encounter ed a pair of monozygotic female twins, one of whom has OCP. In additio n to totally identical physical appearances since birth, the two siste rs have identical blood groups. Methods: The following studies were pe rformed on the patient, her unaffected cotwin sister, and her children : (1) polymorphism of major histocompatibility complex class II genes by DNA typing, (2) sequence analysis of DQ beta gene second and third exons, and (3) serologic evaluation for the presence of anti-basement membrane zone autoantibodies specific for OCP by Western immunoblot wi th the use of skin and conjunctiva lysates as substrates. Result: Both monozygotic twins had the same HLA. haplotypes. The sequence analysis of the second and third exons of DQ beta genes revealed no significan t differences between the proband and her unaffected cotwin. Autoantib odies specific to OCP were detected only in the patient's serum. The s erum of the unaffected cotwin and the other relatives did not demonstr ate the presence of the OCP autoantibody. Conclusion: This isolated fa mily study does not support a single-gene theory for the development o f OCP. It is most likely due to a multigene effect and associated with environmental factors.