Blue cone monochromatism in a female due to skewed X-inactivation

Abstract

Blue cone monochromatism (BCM) is a rare cone dystrophy with recessive X-linked inheritance and therefore diagnosed in males whereas females are clinically unaffected. We present a female with clinically manifested BCM. The diagnosis was genetically verified with the identification of one single red-green OPN1LW/MW hybrid gene harboring a point mutation c.607C>G, p.Cys203Arg that associates with BCM and in addition a completely biased X-inactivation in DNA isolated from full blood and buccal mucosa. The present case illustrates that females may develop symptoms of recessive X-linked eye diseases in rare cases.

KEYWORDS::

• Blue cone monochromatism
• Skewed X-inactivation
• Cone rod dystrophies

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.