Biology, Genetics & Bone Healing MCQs

A 5-year-old girl with severe Osteogenesis Imperfecta (OI) is receiving intravenous pamidronate infusions to increase bone mineral density and reduce fracture frequency. Which of the following best describes the molecular mechanism of action of this medication?

A 12-year-old with multiple fractures has a bone biopsy that demonstrates a distinctive 'fish-scale' lamellation pattern under polarized light microscopy. The patient has shown no clinical improvement with prolonged bisphosphonate therapy. This presentation is most consistent with a mutation in which gene?

A 4-year-old boy with SMA is prescribed Risdiplam. Which of the following accurately describes the administration and mechanism of this medication?

A 6-month-old infant presents with multiple fractures of varying ages, blue sclerae, and generalized osteopenia. Genetic testing reveals a mutation in the COL1A1 gene. Which of the following is the primary mechanism of action of the most commonly prescribed class of medications (bisphosphonates) used to treat this condition?

A 65-year-old female on long-term alendronate therapy for osteoporosis presents with atraumatic thigh pain. Radiographs demonstrate focal lateral cortical thickening of the subtrochanteric femur with a transverse radiolucent line. Which of the following is the primary pathophysiologic mechanism leading to this atypical femur fracture (AFF)?

A neonate is evaluated for short-limbed dwarfism, a 'hitchhiker' thumb, clubfeet, and swelling of the external ear (cauliflower ear). This condition is inherited in an autosomal recessive manner. What is the underlying pathophysiologic defect?

A 12-year-old girl is noted to have excessive shoulder mobility, allowing her to touch her shoulders together anteriorly. She also has delayed eruption of secondary teeth. A mutation in which of the following transcription factors is responsible?

A 35-year-old woman presents with a large, lytic, epiphyseal lesion of the distal femur that extends to the subchondral bone. Biopsy confirms a Giant Cell Tumor of bone. Medical management with denosumab is planned. Denosumab targets which of the following?

A 32-year-old female presents with knee pain. Radiographs show an eccentric, lytic lesion in the distal femoral epiphysis reaching the subchondral bone. Biopsy confirms Giant Cell Tumor of Bone. When utilizing Denosumab for unresectable disease, what is the specific molecular target?

A 7-year-old boy presents with a waddling gait, bilateral knee pain, and mild short stature. Lateral knee radiographs demonstrate a classic "double-layer" patella. A diagnosis of Multiple Epiphyseal Dysplasia (MED) is suspected. A mutation in which gene is most commonly implicated?

An 8-year-old girl is referred for evaluation of unusually delayed tooth eruption. On examination, she is noted to have a large head, delayed closure of cranial sutures, and she is able to easily bring her shoulders together anteriorly. Which genetic mutation is highly characteristic of this condition?

A 32-year-old female presents with knee pain. Radiographs demonstrate an eccentric, lytic, epiphyseal-metaphyseal lesion in the proximal tibia extending to the subchondral bone. Histopathology reveals abundant multinucleated giant cells distributed uniformly among mononuclear stromal cells. The neoplastic mononuclear cells in this tumor typically express high levels of which molecule to drive local bone destruction?

A 12-year-old boy presents with an unusual ability to appose his shoulders anteriorly across his chest. Examination reveals an open anterior fontanelle, delayed eruption of his secondary dentition, and a somewhat prominent forehead. Radiographs show hypoplasia of the clavicles. Which essential transcription factor for osteoblast differentiation is mutated in this condition?

A 30-year-old female presents with mechanical knee pain. Imaging reveals an eccentric, purely lytic epiphyseal lesion of the distal femur extending to the subchondral bone. Biopsy confirms numerous multinucleated giant cells. Which of the following targeted systemic therapies is indicated for unresectable forms of this disease?

A 9-year-old child presents with a waddling gait, bilateral knee pain, and short stature. Radiographs demonstrate small, irregular, fragmented epiphyses and a characteristic "double-layered" patella. A mutation in which of the following genes is most highly associated with this specific classic presentation?

A 35-year-old woman presents with a lytic lesion in the distal femur. Biopsy reveals a benign, locally aggressive tumor characterized by mononuclear stromal cells and numerous multinucleated giant cells. Which of the following describes the cellular target of denosumab in the medical management of this tumor?

A newborn is noted to have a large anterior fontanelle, midface hypoplasia, and excessive mobility of the shoulders, allowing them to be opposed anteriorly. A mutation in the RUNX2 (CBFA1) gene is suspected. What is the primary role of the protein encoded by this gene?