Mumps — branching viva

Opening question

Examiner: Take me through this adolescent. What is the most likely diagnosis, and what is your frame for managing it? ^[5]

Candidate: The most likely diagnosis is mumps with orchitis. The bilateral parotitis with fever and the severe testicular pain in a postpubertal male, in the setting of a university mumps outbreak, is classic — and the fact that he has had two MMR doses does not exclude it, because waning immunity makes vaccinated young adults the outbreak group. My frame is two-layered: manage this adolescent and his complication now, and run the public-health response to stop transmission. The immediate clinical priority, though, is to exclude testicular torsion, because orchitis and torsion overlap and torsion is the surgical emergency. ^{[5] [2]}

Examiner: Why is the postpubertal male at particular risk of orchitis? ^[5]

Candidate: The mumps virus is tropic for glandular duct epithelium, and in a postpubertal host the testicular tissue is mature enough to be seeded by the viraemia, producing oedema and pressure within the tunica and the painful orchitis. In a prepubertal child the gonadal tissue is immature and orchitis does not occur. The biology of the virus is the same; the host turns a nuisance into a complication. ^[5]