WBR0390
| Author | [[PageAuthor::Rim Halaby, M.D. [1]]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Genetics |
| Sub Category | SubCategory::Endocrine |
| Prompt | [[Prompt::A male patient presents to your office to inquire about a disease that is prevalent in his family. He is unsure what the disease is. Instead, he has a pedigree that he created that shows the list of affected and unaffected family members. The patient’s pedigree is shown below. What is the most likely disease in this patient’s family?]] |
| Answer A | AnswerA::Leber’s hereditary optic neuropathy |
| Answer A Explanation | AnswerAExp::Leber’s hereditary optic neuropathy is a mitochondrial disease. All mitochondrial diseases are characterized by maternal transmission to all offspring. |
| Answer B | AnswerB::Albinism |
| Answer B Explanation | AnswerBExp::Albinism has an autosomal recessive mode of inheritance. |
| Answer C | AnswerC::Hypophosphatemic rickets |
| Answer C Explanation | AnswerCExp::Hypophosphatemic rickets has an X-linked dominant mode of inheritance. |
| Answer D | AnswerD::Ocular albinism |
| Answer D Explanation | AnswerDExp::Ocular albinism has an X-linked recessive mode of inheritance. |
| Answer E | AnswerE::Schizophrenia |
| Answer E Explanation | AnswerEExp::Schizophrenia has a polygenic mode of inheritance. |
| Right Answer | RightAnswer::A |
| Explanation | [[Explanation::The pedigree in the vignette shows an X-linked dominant pattern of inheritance. Daughters of affected fathers are also affected. Sons of affected mothers are also affected. Among the list of options, hypophosphatemic rickets, or vitamin D-resistant rickets, is the only option with X-linked dominant inheritance. It is characterized by increased phosphate wasting at the level of renal proximal tubule.
Educational Objective:
X-linked dominant inheritance pattern is characterized by transmission of disease from affected fathers to daughters and affected mothers to sons. Hypophosphatemic rickets is an example of X-linked dominant inheritance pattern that causes phosphate wasting at the level of renal proximal tubule. |
| Approved | Approved::No |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |