Which of the following disease shows autosomal dominant pattern of inheritance?
**Core Concept**
Best's disease, also known as Best vitelliform macular dystrophy, is a rare inherited eye disorder characterized by progressive vision loss due to degeneration of the macula. It is caused by mutations in the VMD2 gene, which encodes a protein crucial for the proper functioning of the retinal pigment epithelium.
**Why the Correct Answer is Right**
Best's disease exhibits an autosomal dominant pattern of inheritance, meaning that a single copy of the mutated VMD2 gene is sufficient to cause the disease. This is because the mutated gene is dominant over the normal gene, leading to the expression of the disease phenotype. In contrast, autosomal recessive diseases require two copies of the mutated gene (one from each parent) to manifest. Best's disease typically presents in childhood or adolescence with central vision loss and is associated with characteristic "egg-yolk" lesions in the macula.
**Why Each Wrong Option is Incorrect**
**Option B:** Bassen-Kornzwig disease, also known as abetalipoproteinemia, is an autosomal recessive disorder characterized by impaired lipid absorption and transport, leading to severe deficiencies of fat-soluble vitamins. It is not associated with an autosomal dominant pattern of inheritance.
**Option C:** Gyrate atrophy is another autosomal recessive disorder, caused by mutations in the OAT gene, which encodes an enzyme involved in the metabolism of ornithine. It is characterized by progressive vision loss due to degeneration of the choroid and retina.
**Option D:** Laurence-Moon-Biedle syndrome, also known as Bardet-Biedl syndrome, is a rare autosomal recessive disorder characterized by obesity, intellectual disability, polydactyly, and progressive vision loss due to retinitis pigmentosa.
**Clinical Pearl / High-Yield Fact**
When evaluating a patient with progressive vision loss, particularly in childhood or adolescence, it is essential to consider the possibility of inherited retinal degenerations, such as Best's disease. Early recognition and genetic counseling can significantly impact the patient's quality of life and reproductive choices.
**✓ Correct Answer: A. Best's disease**