Biology, Genetics & Bone Healing MCQs

A 4-year-old girl presents with progressive genu varum. Laboratory studies show normal serum calcium, normal PTH, elevated alkaline phosphatase, and low serum phosphate. The defective gene in this condition typically leads to excessive production of which of the following?

A newborn presents with micromelic shortening of the limbs, severe clubfeet, "hitchhiker" thumbs, and cystic swelling of the pinnae. Genetic testing would most likely reveal a mutation affecting which of the following processes?

A 7-year-old boy presents with abnormal mobility of his shoulders, allowing him to appose them anteriorly in the midline. Radiographs reveal hypoplastic clavicles and wide cranial sutures.

Which of the following best describes the underlying pathogenesis of this condition?

A 5-year-old boy presents with progressive bowing of his lower extremities and a waddling gait. Laboratory results show normal serum calcium, markedly low serum phosphate, and elevated alkaline phosphatase. Genetic testing reveals a mutation in the PHEX gene. Which of the following is the primary mechanism leading to his bone disease?

A 10-year-old child presents with a history of recurrent fractures, severe anemia, and hepatosplenomegaly. Radiographs show a 'bone-within-a-bone' appearance and generalized extreme sclerosis. The primary cellular defect in this condition involves a failure to form which of the following structures?

A 6-month-old infant presents with failure to thrive, hypotonia, and bowing of the long bones. Radiographs demonstrate wide, irregular physes resembling rickets. Laboratory studies reveal hypercalcemia, hypercalciuria, and markedly decreased serum alkaline phosphatase. Which substance would likely be elevated in the patient's urine?

A 65-year-old woman is prescribed teriparatide for severe osteoporosis. Which of the following patient history elements represents an absolute contraindication to the use of this medication?

An 8-year-old boy from a low-income background presents with bleeding gums, petechiae, and progressive leg pain causing him to refuse to walk. Radiographs show a dense zone of provisional calcification and a ring-shaped radiopacity around the epiphyses. The pathogenesis of this condition involves a failure of which step in collagen synthesis?

A 50-year-old woman presents with bone pain and a pathological fracture of the proximal humerus. Radiographs show multiple lytic bone lesions. Laboratory evaluation reveals serum calcium of 11.5 mg/dL (high), phosphate of 2.1 mg/dL (low), and markedly elevated PTH. Biopsy of a lytic lesion would most likely show which of the following?

A patient with suspected Cleidocranial Dysplasia is undergoing dental and orthopedic evaluation.

In addition to clavicular hypoplasia, what is the most common dental manifestation associated with this RUNX2 mutation?

Which of the following phases of Paget's disease is characterized primarily by prominent, disorganized osteoblastic activity leading to woven bone formation, often manifesting radiographically as cortical thickening and bone enlargement?

A 10-year-old boy presents with unusually prominent forehead, delayed tooth eruption, and the ability to approximate his shoulders anteriorly. Radiographs demonstrate the findings below. What is the affected gene in this disorder?

A 5-year-old child presents with bowing of the legs and short stature. Laboratory evaluation reveals normal serum calcium, decreased serum phosphate, normal PTH, and elevated alkaline phosphatase. Which of the following is the most appropriate medical treatment?

An 65-year-old man presents with increasing hat size, hearing loss, and a bowing deformity of his right tibia. Which of the following best describes the initial cellular abnormality in the pathogenesis of his condition?

An infant presents with recurrent fractures, anemia, and cranial nerve palsies. Radiographs show diffuse, uniformly dense bones with a "bone-within-a-bone" appearance. A defect in which of the following mechanisms is responsible for this condition?

An infant presents with generalized osteosclerosis, hepatosplenomegaly, and pancytopenia. Bone biopsy reveals numerous osteoclasts that completely lack a ruffled border. This form of malignant infantile osteopetrosis is most commonly caused by a mutation affecting which of the following?

A 4-year-old boy presents with progressive bowing of his legs. Laboratory evaluation demonstrates normal serum calcium, low serum phosphate, normal parathyroid hormone, and elevated alkaline phosphatase. Genetic testing reveals a mutation in the PHEX gene. Which of the following represents the primary pathophysiologic mechanism of this disease?

A 9-year-old boy presents with bilateral knee pain, a waddling gait, and difficulty running. Radiographs demonstrate delayed, irregular epiphyseal ossification and a classic "double-layered" patella on the lateral view. A mutation in which of the following genes is most commonly associated with this specific condition?

A 3-year-old girl with recurrent fractures and blue sclerae is started on an intravenous bisphosphonate protocol.

What is the primary cellular mechanism of action of this class of medication?

A 10-year-old girl presents for evaluation of delayed primary tooth loss and failure of permanent dental eruption. On physical exam, she is able to seamlessly appose her shoulders anteriorly in the midline.

The affected gene in this condition primarily orchestrates which of the following processes?