A 25-year-old male presents with a history of exercise intolerance, muscle cramps, and fatigue during physical activity. He notes that after a brief rest, he is able to continue the activity with significantly less discomfort. Laboratory tests reveal elevated serum creatine kinase (CK) levels and myoglobinuria following exercise. Genetic testing confirms a diagnosis of Glycogen Storage Disease Type V (McArdle Disease). Which of the following best explains the patient’s ability to continue physical activity after a short rest?
A 25-year-old male presents to the clinic with complaints of exercise-induced muscle cramps and fatigue. He reports that within a few minutes of intense activity (e.g., running, weightlifting), he experiences severe muscle pain and stiffness, often forcing him to stop. However, after a short rest, he can resume exercise with less pain and improved endurance. He denies any history of cardiac or neurological disease. A forearm exercise test is performed, and blood work reveals: Absent increase in blood lactate levels after exercise Elevated creatine kinase (CK). Which of the following is the most likely diagnosis?
A 2-year-old boy is brought to the pediatric clinic by his parents due to frequent fractures with minimal trauma. His parents report that he broke his femur while crawling and previously fractured his arm while being lifted from a chair. On examination, the child has: Blue sclerae Short stature Mild joint hypermobility No signs of bruising or hepatosplenomegaly X-rays show multiple healed fractures with varying stages of callus formation. Which of the following is the most likely cause of this patient’s condition?
A 27-year-old male presents to the emergency department after falling on his outstretched hand while playing basketball. He reports pain in the anatomical snuffbox and difficulty moving his wrist. X-rays reveal a fracture of the scaphoid bone. What is the most significant complication this patient is at risk for due to this vascular compromise?
A medical student is learning about melanoma and the use of BRAF inhibitors in patients with BRAF V600E mutations. How does a mutation in BRAF affect the RAS-MAPK pathway?
A researcher is studying the effects of a new drug that inhibits the RAS-MAPK pathway for its potential in treating non-small cell lung cancer (NSCLC) with EGFR mutations. At which step in the RAS-MAPK pathway does the drug most likely intervene if it is targeting the MEK protein?
A 55-year-old woman presents with a newly diagnosed metastatic colorectal cancer. Her oncologist is considering targeted therapies based on the mutational status of her tumor. Genetic analysis reveals a mutation in the KRAS gene. Which of the following best describes how a KRAS mutation might affect the RAS-MAPK pathway?
A 62-year-old man with metastatic melanoma is started on vemurafenib, a BRAF inhibitor. His physician explains that his cancer is driven by a BRAF V600E mutation, and the drug works by blocking the MAPK signaling cascade at the level of BRAF, preventing tumor growth. Which of the following best describes the role of BRAF inhibitors like vemurafenib in targeting the RAS-MAPK pathway?
A 48-year-old woman presents with a newly diagnosed pancreatic adenocarcinoma. Molecular testing reveals a KRAS mutation, which is known to drive uncontrolled cell growth. The oncologist explains that this mutation results in constitutive activation of RAS, making the cancer more aggressive and difficult to treat with standard targeted therapies. Which of the following best explains how a KRAS mutation contributes to oncogenesis?
A 55-year-old man presents with a non-small cell lung cancer (NSCLC) diagnosis. Genetic testing reveals a mutation in the KRAS gene, a component of the RAS-MAPK pathway. His oncologist explains that this mutation leads to uncontrolled cell proliferation due to continuous activation of the pathway, making his cancer resistant to certain targeted therapies. Which of the following correctly describes the initial step in RAS-MAPK pathway activation?
