Mumps Parotitis: Bilateral vs Unilateral Presentation
Yes, mumps can present bilaterally, but it more commonly presents as bilateral parotitis; however, unilateral presentation is also well-recognized and occurs less frequently. 1
Clinical Presentation Pattern
The classic presentation of mumps is bilateral parotid gland swelling, though unilateral involvement is explicitly recognized as a less common variant. 1
The ACIP (Advisory Committee on Immunization Practices) 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." 1
Persons with "classical" mumps develop bilateral or (less commonly) unilateral parotitis, with onset averaging 16-18 days after exposure. 1
Important Clinical Caveats
Parotitis is not always present—only 30-40% of mumps infections produce typical acute parotitis, making the absence of gland swelling common. 1, 2
Approximately 15-20% of mumps infections are completely asymptomatic. 1, 2
Up to 50% of infections present with nonspecific or primarily respiratory symptoms without classic parotid involvement. 1, 2
Parotitis occurs most commonly among children aged 2-9 years, while inapparent infection may be more common among adults. 1, 2
Atypical Presentations to Consider
Mumps can affect other salivary glands beyond the parotids, including isolated submandibular gland involvement. 3, 4
Isolated bilateral submandibular gland mumps has been reported, posing diagnostic challenges when typical parotid swelling is absent. 3
Unilateral, synchronous parotid and submandibular gland swelling has been documented, representing a very unusual presentation. 4
Diagnostic Implications
Because parotitis can have multiple infectious and noninfectious causes, and because mumps presentation is variable, serologic confirmation is strongly preferred over clinical diagnosis alone. 1
Laboratory confirmation should be based on: virus isolation from clinical specimens, significant rise in serum mumps IgG antibody titers between acute and convalescent phases, or positive mumps IgM antibody testing. 1
One study found that one-third of persons with clinically diagnosed mumps had no serologic evidence of recent mumps infection, highlighting the importance of laboratory confirmation. 1