## Mumps Orchitis: Age-Related Epidemiology **Key Point:** Mumps orchitis occurs in approximately 20–30% of post-pubertal males infected with mumps virus, with peak incidence in adolescence and early adulthood (13–30 years). ### Age-Related Complications of Mumps | Age Group | Orchitis Risk | Other Complications | Clinical Significance | |-----------|---------------|--------------------|-----------------------| | Infancy (< 2 years) | Rare | Meningitis, encephalitis | Severe systemic disease possible | | Early childhood (2–5 years) | Uncommon (~1–2%) | Parotitis, meningitis | Mostly uncomplicated parotitis | | Adolescence (13–30 years) | **20–30% in males** | Orchitis, oophoritis, deafness | **Peak age for testicular involvement** | | Late adulthood (> 40 years) | Decreases | Meningitis, encephalitis | Rare due to prior immunity | **High-Yield:** Post-pubertal males are at significantly higher risk for orchitis than pre-pubertal boys. This is a classic exam question linking mumps epidemiology to age-related complications. **Clinical Pearl:** Mumps orchitis is usually unilateral (70%) and bilateral in 30% of cases. Infertility is rare even after bilateral orchitis, contrary to common belief. **Mnemonic:** **"MUMPS = Meningitis, Uveitis, Myocarditis, Pancreatitis, Sterility"** — but sterility from mumps is rare; orchitis itself does not typically cause permanent infertility. ### Why Age Matters - **Pre-pubertal boys:** Mumps virus causes parotitis but rarely orchitis (testis not yet fully developed) - **Post-pubertal males:** Mature testicular tissue is susceptible to viral invasion → orchitis in 20–30% - **Hormonal factors:** Testosterone and testicular maturity increase viral tropism [cite:Park 26e Ch 7]
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