What is the differential diagnosis for an elderly female with a history of chronic allergic rhinitis, Hypertension (HTN), Hyperlipidemia, and mild Asthma on albuterol (albuterol) who presents with 2 weeks of nasal drainage that has turned green and a frequent cough, after testing negative for influenza (flu) and Coronavirus Disease 2019 (COVID-19)?

Differential Diagnosis for Elderly Female with Chronic Allergic Rhinitis and Acute-on-Chronic Respiratory Symptoms

The most likely diagnosis is acute bacterial rhinosinusitis (ABRS) superimposed on chronic allergic rhinitis, given the progression from clear to purulent (green) nasal drainage lasting 2 weeks with new-onset cough, particularly in a patient with recurrent annual episodes. 1

Primary Differential Diagnoses

1. Acute Bacterial Rhinosinusitis (ABRS) - Most Likely

• Purulent nasal drainage persisting ≥10 days without improvement meets diagnostic criteria for ABRS 1
• The color change from clear to green indicates purulent drainage, which when accompanied by nasal obstruction or facial symptoms for ≥10 days, strongly suggests bacterial infection 1
• The development of cough after nasal symptoms is consistent with postnasal drainage from sinusitis 1
• Annual recurrence pattern suggests seasonal allergic rhinitis as a predisposing factor for secondary bacterial infection 1

2. Viral Rhinosinusitis (VRS) with Prolonged Course

• Viral upper respiratory infections can produce similar symptoms but typically resolve within 7-10 days 1, 2
• Approximately 7-13% of viral URIs persist beyond 15 days, making this still possible despite 2-week duration 2
• However, the progression to green drainage and worsening cough at 2 weeks makes bacterial superinfection more likely 1

3. Acute Bronchitis

• Acute bronchitis should only be diagnosed after excluding pneumonia, common cold, acute asthma exacerbation, and COPD exacerbation 1
• The patient's history of "bronchitis each year at this time" raises concern for misdiagnosed asthma, as approximately one-third of patients diagnosed with acute bronchitis actually have acute asthma 1
• For patients with ≥2 similar episodes in the past 5 years, 65% can be identified as having mild asthma 1
• Cough with purulent sputum production lasting <3 weeks fits the timeframe 1, 3

4. Asthma Exacerbation - Critical to Consider

• This patient's recurrent annual "bronchitis" diagnoses strongly suggest undiagnosed or undertreated asthma 1
• Allergic rhinitis is present in >75% of patients with asthma, and up to 40% of allergic rhinitis patients develop asthma 4
• The patient has known mild asthma on albuterol only, making exacerbation highly plausible 1
• Viral URI or allergic rhinitis flare can trigger asthma exacerbation with cough as predominant symptom 1, 4

5. Upper Airway Cough Syndrome (UACS) from Allergic Rhinitis

• Postnasal drainage from chronic allergic rhinitis can cause persistent cough without lower airway involvement 1, 5
• The patient's chronic allergic rhinitis predisposes to this condition 1
• However, the acute change to purulent drainage suggests superimposed infection rather than isolated UACS 1

Less Likely but Important Differentials

6. Pertussis (Whooping Cough)

• Should be considered in any patient with persistent cough, especially with recurrent annual pattern 1
• Typically presents with paroxysmal cough, but early stages may mimic viral URI 1
• Less likely given negative flu/COVID testing suggests patient sought testing early, and pertussis typically has more prolonged course

7. Pneumonia

• Must be excluded before diagnosing acute bronchitis 1
• Clinical examination should assess for focal findings, fever, tachypnea, or hypoxia 1
• Chest radiograph indicated only if pneumonia suspected clinically 1

8. Chronic Rhinosinusitis (CRS) Exacerbation

• CRS defined as symptoms lasting >12 weeks 1
• Patient's chronic allergic rhinitis may predispose to CRS 1
• Current acute presentation more consistent with ABRS rather than CRS exacerbation 1

9. Allergic Fungal Rhinosinusitis

• Less common but should be considered in patients with chronic allergic rhinitis and recurrent sinusitis 1
• Typically presents with thick, tenacious secretions and nasal polyposis 1

Critical Clinical Pitfalls

Common Misdiagnosis: "Bronchitis" Instead of Asthma

• The annual recurrence pattern is a red flag for undiagnosed asthma being repeatedly mislabeled as acute bronchitis 1
• Prospective evaluation needed to determine if this represents isolated acute bronchitis versus chronic asthma with acute exacerbations 1

Antibiotic Overuse in Viral Illness

• Rhinosinusitis accounts for more outpatient antibiotic prescriptions than any other diagnosis, with 82% of visits resulting in prescriptions 1
• Most acute rhinosinusitis is viral and self-limited 1, 2
• ABRS criteria must be met before prescribing antibiotics: symptoms ≥10 days without improvement OR worsening within 10 days after initial improvement (double worsening) 1

Undertreated Allergic Rhinitis Leading to Complications

• Uncontrolled allergic rhinitis predisposes to sinusitis, otitis media, and asthma exacerbations 1
• Treating allergic rhinitis with intranasal corticosteroids improves asthma control 6
• Patient on albuterol only suggests inadequate controller therapy if asthma truly present 6

Diagnostic Approach

Key Historical Features to Clarify

• Specific timing of symptom onset relative to seasonal allergen exposure 1
• Presence of facial pain/pressure/fullness accompanying purulent drainage 1
• Character of cough: productive vs. dry, paroxysmal vs. constant, nocturnal predominance 1
• Wheezing, chest tightness, or dyspnea suggesting lower airway involvement 1
• Previous response to bronchodilators during prior "bronchitis" episodes 1

Physical Examination Priorities

• Nasal examination for purulent drainage, mucosal edema, and color (pale/bluish suggests allergic, erythematous suggests infectious) 1
• Lung auscultation for wheezing, prolonged expiration, or focal findings 1
• Vital signs including oxygen saturation and respiratory rate 1
• Sinus percussion/palpation for tenderness 1

When Imaging/Testing Indicated

• Radiographic imaging NOT indicated for uncomplicated acute rhinosinusitis 1
• Chest radiograph only if pneumonia suspected clinically 1
• Consider allergy testing if diagnosis uncertain or treatment fails 1
• Spirometry or peak flow if asthma suspected 1

Management Implications Based on Diagnosis

If ABRS Confirmed (≥10 days purulent drainage + obstruction/facial symptoms)

• Watchful waiting vs. amoxicillin-clavulanate for 5-10 days 1
• Intranasal corticosteroids and saline irrigation for symptom relief 1

If Asthma Exacerbation

• Optimize bronchodilator therapy 1
• Consider inhaled corticosteroid controller therapy given recurrent pattern 6
• Treat underlying allergic rhinitis with intranasal corticosteroids 6

If Viral Rhinosinusitis

• Symptomatic management only 1, 2
• Antibiotics NOT indicated 1, 2
• Expected duration 7-10 days, up to 2 weeks acceptable 2

Regardless of Diagnosis

• Address inadequate allergic rhinitis control with intranasal corticosteroids 1, 7
• Evaluate for underlying asthma given recurrent annual pattern 1, 4
• Patient education about expected symptom duration (2-3 weeks for cough) 3