WBR0277
| Author | [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Genetics, MainCategory::Pathology |
| Sub Category | SubCategory::Oncology |
| Prompt | [[Prompt::An 18-year-old male presents to the physician's office complaining of bone pains and swelling over the right leg just above the knee. He has progressively lost weight over the past 2 months. Medical history indicates that he was treated for eye cancer at the age of 3 years. Which of the following genes is most likely responsible for the conditions presented in this patient?]] |
| Answer A | AnswerA::TP53 gene |
| Answer A Explanation | [[AnswerAExp::The TP53 suppressor gene is associated with DNA repair in the G1 to S phase of the cell cycle and Li-Fraumeni syndrome.]] |
| Answer B | AnswerB::RB gene |
| Answer B Explanation | AnswerBExp::See explanation |
| Answer C | AnswerC::Myc gene |
| Answer C Explanation | [[AnswerCExp::The Myc gene is a proto-oncogene with two variations: L Myc, associated with lung cancer, and N Myc, associated with neuroblastoma. These Myc genes are involved in nuclear transcription.]] |
| Answer D | AnswerD::Abl gene |
| Answer D Explanation | [[AnswerDExp::The Abl gene is associated with chronic myeloid leukemia (CML).]] |
| Answer E | AnswerE::Ret gene |
| Answer E Explanation | [[AnswerEExp::The Ret gene is associated with multiple endocrine neoplasia (MEN) types II and III]] |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::The patient in this scenario has osteosarcoma, with a past history of Retinoblastoma, associated with the RB suppressor gene on chromosome 13. Osteosarcoma commonly affects males 10-20 years of age, and occurs in the metaphysis of distal femur, proximal tibia, and humerus. Osteosarcoma is a connective tissue tumor arising from osteocytes.
Inactivation of the RB suppressor gene may be inherited as an autosomal dominant trait or it may occur sporadically. When osteosarcoma is inherited, one of the alleles on chromosome 13 is inactivated in utero. After birth, only one additional mutation can occur on the remaining allele that results in cancer (called the one-hit theory), increasing the patient's risk of developing a retinoblastoma, the most common malignancy of the eye in children. Additionally, there is an increased risk of developing osteosarcoma between the ages of 10-25 years. |
| Approved | Approved::Yes |
| Keyword | |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |