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- A primary bone dyscrasia involving the otic capsule
- This is the leading cause of conductive hearing loss in adults.
- There are two forms:
- Histologic otosclerosis: asymptomatic form in which abnormal bone spares vital structures of the ear
- Clinical otosclerosis: Abnormal spongy bone involves ossicular chain or other structures, leading to altered physiology.
- System(s) affected: sensory, hearing
- Predominant age
- Clinical onset usually in early 20s
- Peak incidence 3rd to 5th decade
- Predominant gender: female > male (2:1)
- Progression may accelerate during pregnancy.
- Some women first notice hearing loss at this time.
- Histologic form: 4–8% among U.S. Caucasian population; 1% among African Americans
- Histologic form: U.S. Caucasian population: 5,000/100,000; African Americans: 1,000/100,000
- Clinical form: 0.3–0.4%
Etiology and Pathophysiology
- Unknown; possible association with measles virus infection, hormonal factors, cytokine-related inflammation, fluoride metabolism, and oxidative stress
- 50–60% of those affected give positive family history.
- Appears to be transmitted by autosomal dominant gene with variable expressivity
Unknown, possibly measles virus infection
Commonly Associated Conditions
- Van der Hoeve syndrome (rare triad of osteogenesis imperfecta, blue sclera, and otospongiosis)
- Tinnitus, usually low frequency