Editorial

Retinitis Pigmentosa and Common Variable Immunodeficiency Disease: Associated or Separate?

Authors: Margaret M. DeAngelis, PHD

Abstract

Retinitis pigmentosa (RP) and common variable immunodeficiency disease (CVID), both debilitating disorders, are genetically and phenotypically heterogenous.1–3 In this issue of the Southern Medical Journal, Starr and colleagues4 report their clinical findings of three generations in which both RP and CVID appear to occur together. Retinitis pigmentosa, which can be inherited in an autosomal dominant, autosomal recessive or X-linked manner, is as varied in its phenotypic or clinical presentation as CVID. This clinical and genetic heterogeneity can confound the precise mode of disease transmission, as seen in this family. For instance, the disease in this family could be X-linked recessive or autosomal recessive, where both sexes may be equally affected. In a disease characterized by an X-linked inheritance pattern, males have the disease, whereas females usually carry the disease allele, but do not have the disease. However there are exceptions to this and females can be affected or have a milder form of the disease. Usually when females have some form of disease characterized by an X-linked recessive mode of inheritance, the parents are consanguineous, resulting in an affected daughter being homozygous for the disease allele. However, sometimes it is unknown if the affected individual is from a consanguineous union or even if the parents had the disease, because the phenotype could have been mildly expressed and therefore clinically undetected. Further complicating the situation, severity of disease can differ in family members that have the same genotype, in both types of inheritance patterns, X-linked or autosomal recessive. This is because epidemiologic or other genetic contributions may modify the expression of the disease. There are many examples reported in the literature that demonstrate variable expressivity of a genotype within the same family. This has been observed, for example, in patients with X-linked RP,5,6 as well as Usher syndrome, an autosomal recessively inherited disease characterized by RP and deafness.7–9

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References

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