What manifestation is a finding that is specific to pernicious anemia?

Choice A reason: SIADH causes excessive antidiuretic hormone, leading to water retention and dilutional hyponatremia. Low serum sodium results from increased water reabsorption in the kidneys, causing neurological symptoms, making this the correct manifestation.

Choice B reason: Hyperkalemia is not associated with SIADH, which affects water balance, not potassium. Potassium imbalances occur in adrenal or renal disorders, not SIADH’s water retention mechanism, making this choice incorrect.

Choice C reason: Hyperglycemia is unrelated to SIADH, which involves water retention and sodium dilution. Glucose levels are affected by diabetes, not antidiuretic hormone dysfunction, making this choice incorrect for SIADH manifestations.

Choice D reason: Hypertension may occur in SIADH due to fluid overload, but it is not the primary manifestation. Hyponatremia is more specific, as water retention directly dilutes sodium, making this choice incorrect.

Choice A reason: Autosomal dominant disorders affect both genders equally, as they are not sex-linked. Heterozygous individuals express the disorder, not just males, due to the dominant allele on an autosome. The idea of females being carriers only applies to X-linked recessive disorders, making this choice scientifically inaccurate.

Choice B reason: Autosomal dominant disorders are caused by mutations on autosomes, not the Y chromosome, which is sex-linked and primarily affects males. These disorders do not typically skip generations, as the dominant allele is expressed in every affected individual, making this choice incorrect.

Choice C reason: In autosomal dominant disorders, a single mutated allele is sufficient for expression. An affected parent (heterozygous) has one normal and one mutated allele, leading to a 50% chance of passing the mutated allele to each child, causing the disorder. This genetic inheritance pattern makes this the correct choice.

Choice D reason: In autosomal dominant disorders, there is no "carrier" state as in recessive disorders, because heterozygous individuals express the disorder. The 50% probability applies to inheriting the disorder itself, not a carrier genotype, which is a concept relevant to autosomal recessive disorders, making this choice incorrect.