What causes bilateral parotitis?

Bilateral Parotitis is Most Commonly Caused by Mumps Virus

Bilateral parotitis is primarily caused by the mumps virus (paramyxovirus), which is the most common infectious agent responsible for inflammation of both parotid glands. 1

Clinical Presentation of Mumps Parotitis

Mumps typically presents with the following characteristics:

• Bilateral or unilateral parotid gland swelling (though bilateral is more common)
• Fever and prodromal symptoms preceding gland swelling
• Incubation period of 16-18 days after exposure
• 15-20% of infections may be asymptomatic 2

The parotid swelling in mumps is characterized by:

• Pain and tenderness of the affected gland(s)
• Difficulty or pain when chewing
• Swelling that can last 7-10 days
• Often preceded by fever, headache, malaise, and myalgia

Differential Diagnosis of Bilateral Parotitis

While mumps is the most common cause of bilateral parotitis, other etiologies include:

1. Viral causes:

   • Epstein-Barr virus (EBV)
   • Parainfluenza viruses (particularly type 3)
   • Influenza A and B viruses
   • Coxsackievirus
   • Adenovirus
   • Enterovirus 3, 4

2. Bacterial causes:

   • Acute suppurative parotitis (typically Staphylococcus aureus)
   • Streptococcal species
   • Anaerobic bacteria (Peptostreptococcus, Bacteroides) 3

3. Other causes:

   • Medication-induced (anticholinergics, phenothiazines)
   • Sjögren's syndrome
   • Sarcoidosis
   • Metabolic disorders (diabetes, alcoholism)

Diagnostic Approach

To confirm mumps as the cause of bilateral parotitis:

1. Clinical evaluation: Assess for characteristic bilateral parotid swelling with associated systemic symptoms

2. Laboratory testing:

   • RT-PCR of oral/buccal swab specimens (preferably collected from the parotid duct/Stensen's duct) 5
   • Serology for mumps IgM antibodies
   • Paired acute and convalescent serum samples to demonstrate a 4-fold rise in mumps IgG antibodies 5

3. Timing of specimen collection:

   • Buccal/oral swab: Collect within 3 days of symptom onset for optimal viral detection
   • Serum for serology: Collect acute sample as soon as possible after symptom onset and convalescent sample 2-3 weeks later 5

Complications of Mumps

Mumps can lead to several complications:

• Aseptic meningitis (up to 15% of cases)
• Orchitis (20-30% of postpubertal males)
• Oophoritis (5% of postpubertal females)
• Pancreatitis (more common in adults)
• Sensorineural hearing loss (rare but serious complication)
• Conjunctivitis (uncommon) 2, 6

Prevention and Management

1. Prevention:

   • MMR (measles, mumps, rubella) vaccination is the most effective preventive measure
   • Two doses of MMR vaccine provide better protection against mumps
   • Most adults born before 1957 are likely naturally immune 2

2. Management:

   • Supportive care (no specific antiviral therapy is available)
   • Analgesics for pain relief
   • Adequate hydration
   • Warm or cold compresses to reduce parotid pain and swelling
   • Isolation of infected individuals to prevent spread 2

Clinical Pearls and Pitfalls

• Pitfall: Assuming all cases of bilateral parotitis are mumps. Always confirm diagnosis, especially in vaccinated individuals.
• Pearl: The timing of specimen collection is crucial for accurate diagnosis. Samples collected within the first 3 days of parotitis have the highest yield for viral detection.
• Pitfall: Failing to consider other viral etiologies in vaccinated individuals with parotitis. Studies show that up to 72.3% of suspected mumps cases in vaccinated individuals may be caused by other viruses 4.
• Pearl: Mumps can still occur in previously vaccinated individuals due to waning immunity or vaccine failure, though symptoms are typically milder.