What is the likely diagnosis and recommended treatment for a 27-year-old male with a 1-week history of respiratory infection (cough and fever with runny nose), who has since developed left jaw swelling and pain when opening his mouth, but has no difficulty swallowing and no current fever?

Acute Parotitis (Mumps-like Illness) Following Viral Upper Respiratory Infection

Most Likely Diagnosis

This patient has acute viral parotitis, most likely post-viral or mumps (if unvaccinated), presenting as unilateral parotid gland swelling with trismus following a viral upper respiratory infection. The timeline—respiratory symptoms followed 4 days later by unilateral jaw/preauricular swelling with pain on jaw opening—is classic for parotid gland inflammation 1, 2.

Clinical Reasoning

The key diagnostic features pointing to parotitis include:

• Unilateral swelling in the preauricular/jaw region (where the parotid gland is located) that developed after resolution of fever from the initial viral illness 1, 3
• Pain with jaw opening (trismus) is characteristic of parotid inflammation, as the gland is compressed during mandibular movement 3, 4
• No difficulty swallowing helps distinguish this from pharyngeal or submandibular pathology 3
• Temporal relationship: parotitis developing 3-4 days after a viral URI is well-documented, particularly with influenza and other respiratory viruses 1, 2

The absence of current fever and the self-limited nature of the initial respiratory illness (resolved after 4 days with symptomatic treatment) suggests this was a typical viral URI 5. Parotitis can occur as a post-viral complication or concurrent viral infection of the salivary glands 1, 2.

Differential Diagnosis Considerations

Acute bacterial parotitis is less likely given:

• No current fever (bacterial parotitis typically presents with high fever and systemic toxicity) 3
• Unilateral presentation in a young, otherwise healthy patient (bacterial parotitis more common in elderly, dehydrated, or hospitalized patients) 3
• No mention of purulent discharge from Stensen's duct 3

Acute bacterial rhinosinusitis (ABRS) does not fit because:

• The patient's respiratory symptoms lasted only 7 days total (fever resolved at day 4), which is less than the 10-day threshold for ABRS 5
• No "double worsening" pattern after initial improvement 5
• The jaw swelling location (preauricular, near ear) is anatomically inconsistent with sinusitis, which causes facial pain/pressure over the sinuses 5

Recommended Management

Initial Conservative Approach

For uncomplicated viral parotitis, treatment is supportive care without antibiotics:

• Hydration and sialagogues: Encourage increased fluid intake and use of sour candies or lemon drops to stimulate salivary flow, which helps clear the duct 3, 4
• Warm compresses to the affected area for symptomatic relief 3
• NSAIDs (continue ibuprofen) for pain and inflammation control 3
• Massage of the gland from posterior to anterior to promote drainage 3, 4
• Good oral hygiene to prevent secondary bacterial infection 3

When to Escalate to Antibiotic Therapy

Antibiotics are indicated ONLY if bacterial superinfection develops, evidenced by:

• Recurrent or persistent fever (>39°C) after initial improvement 3
• Purulent discharge from Stensen's duct (parotid duct opening opposite upper second molar) 3
• Severe systemic toxicity or worsening symptoms despite 48-72 hours of conservative management 3
• Fluctuance suggesting abscess formation 3

If bacterial parotitis is suspected, the antibiotic choice should cover Staphylococcus aureus and anaerobes (the most common pathogens):

• First-line: Amoxicillin-clavulanate 875/125 mg twice daily 6, 3
• Penicillin allergy: Clindamycin 300 mg three times daily 6, 3

Critical Red Flags Requiring Urgent Evaluation

• Severe trismus preventing oral intake (may require IV hydration) 3
• Orbital symptoms (vision changes, proptosis, ophthalmoplegia) suggesting spread of infection 7
• Severe headache or altered mental status suggesting intracranial extension 7
• Bilateral massive swelling with respiratory compromise 3

Important Clinical Pitfalls to Avoid

Do NOT prescribe antibiotics for uncomplicated viral parotitis. The patient's current presentation—unilateral parotid swelling without fever, purulent discharge, or systemic toxicity—does not meet criteria for bacterial infection 3. Unnecessary antibiotic use increases resistance and adverse effects without benefit 5.

Do NOT confuse this with ABRS requiring antibiotics. The respiratory symptoms resolved appropriately for a viral URI (symptoms improved by day 4-7), and the anatomic location of swelling (parotid region) is distinct from sinusitis 5.

Do NOT assume mumps without vaccination history. If the patient is unvaccinated or incompletely vaccinated, mumps should be considered and public health notification may be required 2. However, post-viral parotitis from influenza or other respiratory viruses is increasingly recognized 1, 2.

Follow-Up Recommendations

• Reassess in 48-72 hours if symptoms do not improve with conservative management 3, 4
• Return immediately if fever develops, purulent discharge appears, or swelling worsens significantly 3
• Expected course: Viral parotitis typically resolves within 7-10 days with supportive care alone 3, 4