What is the diagnosis and treatment for a teenager with a painful lump around the jaw and a viral infection, possibly mononucleosis or viral parotitis?

Painful Jaw Lump in a Teenager with Viral Infection

The most likely diagnosis is viral parotitis (mumps) or infectious mononucleosis with cervical/parotid lymphadenopathy, and you should obtain laboratory confirmation with mumps IgM antibody testing and/or heterophile antibody testing before initiating treatment, which is primarily supportive care. 1, 2

Differential Diagnosis

The painful lump around the jaw in a teenager with viral infection most commonly represents:

• Viral parotitis (mumps): Presents with bilateral or unilateral parotid swelling, fever, headache, and malaise, with onset 16-18 days after exposure 3, 1
• Infectious mononucleosis (EBV): Characterized by the classic triad of fever, pharyngitis, and cervical lymphadenopathy, most commonly affecting adolescents aged 15-24 years 2, 4
• Other viral causes: Adenovirus, influenza, parainfluenza, and other respiratory viruses can cause pharyngitis with associated lymphadenopathy 3, 5

Critical pitfall: Clinical diagnosis alone is unreliable—misdiagnoses occur in approximately one-third of cases, so laboratory confirmation is essential 1

Diagnostic Approach

Immediate Laboratory Testing

For suspected mumps:

• Obtain mumps IgM antibody testing 1
• Collect parotid duct (Stensen duct) or buccal swabs for viral PCR within 9 days of symptom onset 3, 1
• Consider urine PCR, which remains positive for at least 5 days after oral detection 1

For suspected infectious mononucleosis:

• Order complete blood count with differential looking for >40% lymphocytes and >10% atypical lymphocytes 2, 4
• Perform rapid heterophile antibody (Monospot) test, which has 87% sensitivity and 91% specificity 2
• If Monospot is negative but clinical suspicion remains high, order EBV viral capsid antigen IgM antibody testing, which is more sensitive and specific 2, 6

Important caveat: The heterophile antibody test can be falsely negative in children younger than 5 years and during the first week of illness 2

Clinical Features That Guide Diagnosis

Favor mumps if:

• Bilateral or unilateral parotid swelling is present 3, 1
• Patient is a teenager (peak age 2-9 years for parotitis, but complications more common in adolescents/adults) 3
• Fever, headache, and myalgia precede parotid swelling 3

Favor infectious mononucleosis if:

• Posterior cervical lymphadenopathy is prominent 2, 4
• Pharyngitis with tonsillar enlargement is present 2, 4
• Periorbital or palpebral edema (occurs in one-third of patients) 4
• Splenomegaly or hepatomegaly on examination 4
• Elevated liver enzymes increase suspicion even with negative Monospot 2

Management

Infection Control (for mumps)

Implement immediately:

• Droplet precautions with isolation for 5 days after onset of parotitis 1
• Use standard precautions plus gown and gloves for patient contact 1
• Ensure only healthcare personnel with documented immunity provide care 1

Supportive Treatment

Do not prescribe antibiotics for confirmed viral etiology, as this contributes to antimicrobial resistance without clinical benefit 1

Provide symptomatic relief:

• Systemic analgesics (ibuprofen or acetaminophen) for pain and fever 7
• Warm saline mouthwashes to cleanse the oral cavity 7
• Topical analgesics such as benzydamine hydrochloride rinses for painful oral lesions 7
• Bed rest as tolerated with reduction of activity 4

Activity Restrictions (for infectious mononucleosis)

Patients must avoid contact sports or strenuous exercise for 8 weeks or while splenomegaly persists to prevent splenic rupture, which occurs in 0.1-0.5% of cases and is potentially life-threatening 4

Current guidelines recommend no athletic activity for 3 weeks from symptom onset, with shared decision-making for return to activity 2

Monitoring for Complications

For mumps:

• Assess for orchitis in postpubertal males (occurs in up to 38% of cases) 3, 1
• Monitor for signs of aseptic meningitis/meningoencephalitis 1
• Watch for pancreatitis developing at days 3-5 of illness 1
• Be alert for hearing loss, particularly in children 1

For infectious mononucleosis:

• Monitor for splenic rupture (most feared complication) 6, 4
• Watch for airway obstruction from tonsillar enlargement 4
• Assess for neurologic, hematologic, or hepatic complications 6

Special Considerations

Test for HIV in all patients with parotitis, regardless of apparent risk factors, as HIV can present with parotid swelling 1

For pregnant women with mumps in the first trimester, close monitoring is required due to increased risk of fetal death 3, 1

Do not administer MMR vaccine expecting immediate post-exposure prophylaxis, though vaccination should still be offered to non-immune contacts for future protection 1

Avoid prescribing amoxicillin or ampicillin if infectious mononucleosis is suspected, as these antibiotics cause a characteristic rash in 90% of patients with EBV infection 4