Biology, Genetics & Bone Healing MCQs

A 14-year-old boy has multiple painless bony protuberances around his knees and shoulders. Genetic testing reveals a mutation in the EXT1 gene. This mutation primarily affects which of the following cellular processes?

A 4-year-old girl with a history of multiple low-energy fractures, blue sclerae, and dentinogenesis imperfecta is started on pamidronate. What is the primary mechanism of action of this medication in treating her condition?

A 15-year-old boy presents with the ability to appose his shoulders at the midline. He has delayed eruption of permanent teeth and an unusually wide face. Radiographs show absent clavicles. This condition is primarily due to a defect in which of the following?

A 6-year-old boy presents with recurrent fractures, anemia, and hepatosplenomegaly. Radiographs reveal a 'bone-within-a-bone' appearance and generalized osteosclerosis. What is the most definitive curative treatment for the underlying systemic disease?

An infant presents with failure to thrive, hepatosplenomegaly, and severe anemia. Radiographs show diffusely dense bones with a "bone-within-bone" appearance in the metaphyses. A mutation impairing which of the following cellular mechanisms is most likely responsible?

Denosumab is increasingly used in the neoadjuvant management of unresectable or complex giant cell tumors of bone.

What is the specific target of this monoclonal antibody?

A 15-year-old patient is evaluated for delayed dental eruption, open cranial sutures, and abnormal shoulder mobility, allowing them to approximate their shoulders anteriorly. This autosomal dominant condition is caused by a mutation in the RUNX2 (CBFA1) gene. This gene normally controls the differentiation of which cell type?

A 65-year-old male presents with increasing hat size, asymmetric hearing loss, and bowing of his right tibia. Laboratory testing reveals markedly elevated alkaline phosphatase with normal serum calcium and phosphorus. Which phase of this specific disease process is characterized by intense, unregulated osteoclastic resorption?

A 28-year-old female presents with severe knee pain. Radiographs reveal an eccentric, lytic epiphyseal-metaphyseal lesion in the proximal tibia.

Biopsy is consistent with a giant cell tumor of bone. Which of the following describes the primary neoplastic cell population in this lesion?

A 7-year-old girl is evaluated for delayed eruption of secondary teeth. Examination reveals a persistently open anterior fontanelle, hypermobility of the shoulders allowing them to meet in the midline, and short stature. The gene responsible for this condition is critical for the differentiation of which cell type?

A 32-year-old female presents with progressive knee pain. Radiographs reveal an eccentric, lytic epiphyseal lesion extending to the subchondral bone in the distal femur.

Biopsy confirms a giant cell tumor. She is treated preoperatively with a monoclonal antibody to facilitate joint salvage. What is the primary mechanism of action of this medication?

A 25-year-old female presents with progressive knee pain. Radiographs reveal an eccentric, expansile, lytic lesion in the distal femoral epiphysis extending to the subchondral bone plate. Biopsy confirms a giant cell tumor of bone.

If pharmacological therapy with denosumab is considered, this drug specifically targets which of the following mechanisms in this pathology?

A 10-year-old boy is referred for delayed eruption of his permanent teeth, prominent frontal bossing, and excessive shoulder mobility. Radiographs demonstrate hypoplastic clavicles and delayed ossification of the pubic symphysis. A mutation in which of the following transcription factors is responsible for this condition?

A 12-year-old boy presents with multiple hard, painless masses around his knees and ankles. Radiographs demonstrate multiple bone excrescences pointing away from the joints, with continuity of the medullary cavity into the lesions. What is the underlying pathogenesis of this condition?

A 65-year-old man presents with severe back pain. Radiographs show multiple dense, osteoblastic lesions throughout the lumbar spine and pelvis. Laboratory evaluation reveals a significantly elevated serum prostate-specific antigen (PSA). The osteoblastic nature of these skeletal metastases is primarily driven by tumor secretion of which factor?

A newborn is evaluated in the NICU for marked shortening of all limbs, proximally placed "hitchhiker" thumbs, severe clubfeet, and distinct cystic swelling of the pinnae (cauliflower ears). Radiographs show short, thick long bones and a normal skull. The underlying genetic mutation in this condition primarily impairs which cellular process?

A 14-year-old with multiple bony protuberances around his knees and shoulders has a known genetic condition. What is the primary cellular function of the mutated genes responsible for this disorder?

Which of the following genetic abnormalities is most consistently associated with the pathogenesis of Hereditary Multiple Exostoses (HME), and what is the resulting pathophysiologic defect?

A 45-year-old male presents with spontaneous, progressive shoulder weakness and deformity. Radiographs demonstrate complete disappearance of the proximal humerus and clavicle.

Which histological finding is pathognomonic for this disease process?