Final answer:
Mosaicism is the least likely explanation for a patient likely having Marfan syndrome, as Marfan is typically inherited in an autosomal dominant pattern, where symptoms occur with just one mutated gene. Spontaneous mutation, inheritance from a distant relative, or incomplete penetrance are more plausible explanations.
Step-by-step explanation:
The least likely explanation for a patient likely having Marfan syndrome following a pre-employment physical is (d) Mosaicism. Marfan syndrome is inherited in an autosomal dominant pattern, meaning that an individual with a mutation in the gene responsible for Marfan syndrome will exhibit symptoms even if they have only one copy of the mutated gene. Among the options provided:
- Spontaneous mutation: This can occur and cause Marfan syndrome even without a family history.
- Inheritance from a distant relative: While possible, Marfan syndrome could be traced back to a distant relative who carries the gene.
- Incomplete penetrance: Sometimes individuals who carry an autosomal dominant gene might not show symptoms, which is known as incomplete penetrance.
- Mosaicism: This involves an individual having two or more populations of cells with different genotypes in their body, which is less likely to lead to a diagnosis of Marfan syndrome.
Therefore, mosaicism is the least likely explanation for the presence of symptoms consistent with Marfan syndrome in the patient described.