Ocular cicatricial pemphigoid. A case report of monozygotic twins discordant for the disease

K. Bhol, I. Udell, N. Haider, J. J. Yunis, A. Mohimen, R. Neuman, C. Grasso, A. R. Ahmed and S. Foster
Department of Dermatology, Boston Mass. University School of Medicine.

OBJECTIVE: To identify the major histocompatibility complex markers and 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 affects the conjunctiva and other squamous epithelium. It is associated with the major histocompatibility complex class II alleles that are presumed to provide enhanced susceptibility to the disease. We encountered a pair of monozygotic female twins, one of whom has OCP. In addition to totally identical physical appearances since birth, the two sisters have identical blood groups. METHODS: The following studies were performed 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 with 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 significant differences between the proband and her unaffected cotwin. Autoantibodies specific to OCP were detected only in the patient's serum. The serum of the unaffected cotwin and the other relatives did not demonstrate the presence of the OCP autoantibody. CONCLUSION: This isolated family study does not support a single-gene theory for the development of OCP. It is most likely due to a multigene effect and associated with environmental factors.