What is the inheritance pattern of Bruton's agammaglobulinemia?

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Multiple Choice

What is the inheritance pattern of Bruton's agammaglobulinemia?

Explanation:
Bruton’s agammaglobulinemia is inherited in an X-linked recessive pattern. The disease-causing mutation is in the BTK gene on the X chromosome, which is essential for proper maturation of B cells. Because males have only one X chromosome, a single mutated BTK allele will cause the condition, leading to very low or absent B cells and immunoglobulins and resulting in recurrent bacterial infections early in life. Females have two X chromosomes, so a single mutated BTK allele typically doesn’t produce disease because the other healthy copy can compensate; they usually become carriers who can pass the mutation to their offspring. An affected male has a 50% chance of passing the mutation to each daughter (who becomes a carrier) and a 0% chance to his sons (who inherit his Y chromosome). If a mother is a carrier, about half of her sons may be affected, and half of her daughters may be carriers. This pattern explains why the condition predominantly affects males and why affected families often show carrier females. Other inheritance patterns don’t fit this scenario: autosomal inheritance would affect both sexes more evenly and doesn’t explain the strong male predominance; autosomal recessive needs two mutated copies; mitochondrial inheritance would pass from mothers to all children regardless of sex.

Bruton’s agammaglobulinemia is inherited in an X-linked recessive pattern. The disease-causing mutation is in the BTK gene on the X chromosome, which is essential for proper maturation of B cells. Because males have only one X chromosome, a single mutated BTK allele will cause the condition, leading to very low or absent B cells and immunoglobulins and resulting in recurrent bacterial infections early in life. Females have two X chromosomes, so a single mutated BTK allele typically doesn’t produce disease because the other healthy copy can compensate; they usually become carriers who can pass the mutation to their offspring.

An affected male has a 50% chance of passing the mutation to each daughter (who becomes a carrier) and a 0% chance to his sons (who inherit his Y chromosome). If a mother is a carrier, about half of her sons may be affected, and half of her daughters may be carriers. This pattern explains why the condition predominantly affects males and why affected families often show carrier females.

Other inheritance patterns don’t fit this scenario: autosomal inheritance would affect both sexes more evenly and doesn’t explain the strong male predominance; autosomal recessive needs two mutated copies; mitochondrial inheritance would pass from mothers to all children regardless of sex.

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