Can parotitis from mumps in adults present unilaterally or bilaterally?

Mumps Parotitis: Unilateral vs Bilateral Presentation

Mumps parotitis in adults can present either bilaterally (classic presentation) or unilaterally (less common variant), with both patterns explicitly recognized as legitimate manifestations of the disease. 1, 2

Clinical Presentation Patterns

The Advisory Committee on Immunization Practices formally defines a clinical case of mumps as "acute onset of unilateral or bilateral tender, self-limited swelling of the parotid or other salivary gland lasting ≥2 days," making clear that both presentations are diagnostic. 2

Bilateral vs Unilateral Distribution

• Bilateral parotitis is the classic and more common presentation of mumps infection 1, 2, 3
• Unilateral parotitis occurs less commonly but is a well-recognized variant of mumps 1, 2, 4
• The typical onset occurs 16-18 days after exposure, regardless of whether involvement is unilateral or bilateral 1, 2

Critical Clinical Caveats

Parotitis May Be Absent Entirely

A major pitfall in mumps diagnosis is assuming parotid swelling must be present:

• Only 30-40% of mumps infections produce typical acute parotitis (bilateral or unilateral) 1, 5, 2
• 15-20% of infections are completely asymptomatic 1, 5, 2
• Up to 50% present with nonspecific or primarily respiratory symptoms without any parotid involvement 1, 5, 2
• Parotitis is absent in 10-30% of symptomatic cases 6

Age-Related Presentation Differences

• Parotitis occurs most commonly among children aged 2-9 years 1, 2
• Inapparent infection (without parotid swelling) may be more common among adults than children 1, 2
• Serious complications are more common and severe in adults than children, making adult cases particularly important to identify even without classic parotitis 1, 5

Diagnostic Implications

Laboratory Confirmation Is Essential

Because parotitis has multiple infectious and noninfectious causes, and because mumps presentation is highly variable, serologic confirmation is strongly preferred over clinical diagnosis alone. 2

• One study found that one-third of persons with clinically diagnosed mumps had no serologic evidence of recent mumps infection 2
• Laboratory confirmation should be based on: virus isolation, significant rise in serum mumps IgG antibody titers between acute and convalescent phases, or positive mumps IgM antibody testing 2
• Suitable specimens include serum, saliva, urine, and cerebrospinal fluid 6

Unusual Presentations Documented

• Unilateral, synchronous swelling of both parotid and submandibular glands has been documented, though very rare 7
• Serious complications of mumps can occur without any evidence of parotitis 1

Adult-Specific Complications to Monitor

Since you're asking about adults specifically, be aware that most serious complications are more common among adults than children: 1

• Orchitis occurs in up to 38% of postpubertal men, though sterility is rare 1, 5
• Aseptic meningitis affects 4-6% of cases 1, 5
• Oophoritis can occur in postpubertal females 5
• Sensorineural deafness can be sudden, bilateral, and permanent 1, 5
• Pancreatitis may develop 5