Histology USMLE Step 1 Practice Question
A 42-year-old woman presents to otolaryngology with progressive bilateral low-frequency sensorineural hearing loss over the past 5 years. She reports a family history of similar hearing loss in her mother and maternal grandmother. Vital signs are normal. Genetic testing reveals a heterozygous mutation in COL2A1. Bone conduction thresholds are elevated at low frequencies (250-1000 Hz). A bone biopsy from the temporal bone region shows collagen fibrils with irregular diameter variation (ranging from 40-120 nm), abnormal spacing patterns, and areas of disrupted fibril organization compared to normal architecture. Imaging excludes otosclerosis and semicircular canal dehiscence. Which of the following best explains these histopathologic findings?
Answer choices
- AAbnormal cross-linking of type I collagen affecting osteoid matrix mineralization and auditory ossicles
- BDefective type III collagen affecting the walls of cochlear blood vessels and spiral ligament
- CDisorganized type II collagen fibrils affecting the tectorial membrane and cartilaginous structures of the inner earCorrect answer
- DDefective type IV collagen affecting the basilar membrane and cochlear epithelial basement membranes
- EAbnormal type XI collagen affecting the fibrocartilaginous components of the middle ear
- FDefective elastin affecting elastic fibers in the cochlear partition and round window membrane
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