What is the possible diagnosis for a patient with recurrent parotid (parotid gland) swelling, skin pruritus, abdominal pain, cough, dyspnea, mild peripheral eosinophilia, elevated IgE (Immunoglobulin E) levels, sialectasis, and chronic parotitis?

Allergic Bronchopulmonary Aspergillosis (ABPA) with Possible Eosinophilic Sialodochitis

The most likely diagnosis is Allergic Bronchopulmonary Aspergillosis (ABPA), which explains the respiratory symptoms, eosinophilia, elevated IgE, and sialectasis findings, with the recurrent parotid swelling representing either concurrent eosinophilic sialodochitis or a manifestation of systemic allergic disease. 1, 2

Primary Diagnosis: ABPA

Diagnostic Criteria Met

This patient fulfills the essential diagnostic criteria for ABPA as defined by the 2024 ISHAM guidelines 1:

• Elevated serum total IgE ≥500 IU/mL (criterion met) 1
• Blood eosinophil count ≥500 cells/μL (mild peripheral eosinophilia present) 1
• Respiratory symptoms: cough and dyspnea are characteristic presenting features 1
• Chronic parotitis with sialectasis: while unusual, this may represent concurrent eosinophilic involvement 2

Supporting Clinical Features

The constellation of symptoms strongly supports ABPA 1:

• Skin pruritus indicates systemic allergic/atopic disease, present in 66% of patients with eosinophilic conditions 2
• Abdominal pain can occur with systemic eosinophilic disorders and hypereosinophilic syndromes 1
• Cough and dyspnea are cardinal respiratory manifestations of ABPA, occurring in virtually all symptomatic patients 1
• Mild peripheral eosinophilia (≥500 cells/μL) is a required diagnostic criterion 1

Critical Next Steps for ABPA Confirmation

Immediate diagnostic workup required 1:

• Aspergillus fumigatus-specific IgE and IgG (Aspergillus precipitins) - essential for diagnosis 1
• Thin-section chest CT scan to evaluate for central bronchiectasis (inner two thirds of chest), mucus plugging, high-attenuation mucus, or fleeting infiltrates 1
• Aspergillus skin prick test if serology unavailable 1
• Pulmonary function testing to document reversible airflow obstruction 1

Secondary Diagnosis: Eosinophilic Sialodochitis

Explaining the Parotid Involvement

The recurrent parotid swelling with sialectasis and chronic parotitis, combined with systemic eosinophilia and elevated IgE, strongly suggests eosinophilic sialodochitis 2:

• Eosinophilic sialodochitis presents with recurrent salivary gland swelling in 78% of reported cases, predominantly affecting females (F:M = 2.3:1) 2
• Blood eosinophilia is present in 71% of eosinophilic sialodochitis cases 2
• Atopic disease/allergic symptoms occur in 63-66% of patients 2
• Ductal dilatation (sialectasis) is documented in 82% of cases on imaging 2

Distinguishing from Juvenile Recurrent Parotitis

While juvenile recurrent parotitis (RPC) causes recurrent parotid swelling with sialectasis 3, 4, this diagnosis is less likely because:

• RPC typically affects children aged 3-6 years and resolves by age 22 4
• RPC is not associated with systemic eosinophilia, elevated IgE, or respiratory symptoms 3, 4
• The presence of systemic allergic manifestations points toward eosinophilic sialodochitis 2

Differential Diagnoses to Exclude

Eosinophilic Granulomatosis with Polyangiitis (EGPA/Churg-Strauss)

Must be excluded given the overlap of features 1, 5:

• EGPA presents with asthma, eosinophilia (usually >1500 cells/μL or >10%), and systemic vasculitis 5
• Key distinguishing features: EGPA typically has marked eosinophilia (not mild), peripheral neuropathy, cardiac involvement, and ANCA positivity in 40% 1, 5
• The "mild" eosinophilia described here is more consistent with ABPA 1
• Check: ANCA, cardiac evaluation (echocardiogram, troponin), and neurologic examination 1

Hypereosinophilic Syndrome (HES)

Consider but less likely 1, 6:

• HES requires absolute eosinophil count ≥1.5 × 10⁹/L for >3 months with end-organ damage 6
• The description of "mild" eosinophilia suggests counts below this threshold 6
• HES can cause cardiac (endomyocardial fibrosis), pulmonary, and GI involvement 1
• If eosinophil count ≥1.5 × 10⁹/L: urgent hematology referral and cardiac evaluation required 6

Parasitic Infection

Must be systematically excluded 6:

• Helminth infections account for 19-80% of eosinophilia in travelers/migrants 6
• Strongyloides stercoralis can persist lifelong and cause fatal hyperinfection if immunosuppressed 6
• Obtain: detailed travel history, three separate stool specimens for ova and parasites, Strongyloides serology 6
• Critical: Do not start corticosteroids until parasitic infection excluded 6

Treatment Algorithm

Step 1: Confirm ABPA Diagnosis (Before Treatment)

Do not initiate corticosteroids until parasitic infection excluded 6:

• Complete parasitic workup (stool ova/parasites × 3, Strongyloides serology) 6
• Obtain Aspergillus fumigatus-specific IgE and IgG 1
• Chest CT to document bronchiectasis or other ABPA features 1

Step 2: Initiate ABPA Treatment

Corticosteroids are the mainstay of ABPA therapy 1:

• Prednisone 0.5 mg/kg/day for 1 week, then 0.5 mg/kg every other day 1
• Attempt to discontinue after 6 weeks, monitoring for symptom recurrence 1
• Monitor serum total IgE levels: declining IgE correlates with treatment response, rising IgE often precedes exacerbations 1
• Most patients develop mild asthma symptoms during taper, controlled with inhaled bronchodilators/corticosteroids 1

Step 3: Address Eosinophilic Sialodochitis

Treatment options for recurrent parotid swelling 2:

• Anti-allergic medications (antihistamines, leukotriene inhibitors) used in 58% of cases 2
• Systemic glucocorticoids (already initiated for ABPA) effective in 25% 2
• Duct cannulation with irrigation and/or steroid injection in 36% of refractory cases 2
• Conservative management initially, as symptoms may improve with systemic corticosteroid therapy for ABPA 2

Critical Pitfalls to Avoid

Pitfall 1: Starting Corticosteroids Before Excluding Strongyloides

Fatal hyperinfection syndrome can occur if Strongyloides is present and corticosteroids initiated 6:

• Always complete parasitic workup first, especially with any travel history 6
• Strongyloides can persist asymptomatically for decades 6

Pitfall 2: Relying on Peripheral Eosinophil Count Alone

Peripheral eosinophilia may not reflect tissue eosinophilia 7:

• In eosinophilic esophagitis, only 10-50% of adults have peripheral eosinophilia 7
• Tissue diagnosis (lung biopsy, BAL) may be needed in atypical cases 8
• Recent corticosteroid use artificially lowers blood eosinophil counts 5

Pitfall 3: Missing Central Bronchiectasis on Chest X-ray

Chest CT is superior to chest radiograph for detecting bronchiectasis 1:

• Central bronchiectasis (inner two-thirds of chest) is pathognomonic for ABPA in asthmatic patients 1
• Chest X-ray may show "ring signs" or "tram lines" but CT is diagnostic standard 1

Pitfall 4: Assuming Parotid Swelling is Unrelated

Eosinophilic sialodochitis is a recognized entity in atopic patients 2:

• The combination of recurrent parotid swelling, sialectasis, eosinophilia, and atopy defines this condition 2
• This is not simple juvenile recurrent parotitis given the systemic features 3, 4

Monitoring and Follow-up

Serial serum total IgE measurements guide ABPA management 1:

• IgE levels decline with successful treatment 1
• Rising IgE often precedes clinical exacerbations by weeks 1
• Monitor every 6-8 weeks during treatment, then every 2-3 months in remission 1

Assess for end-organ damage if eosinophilia persists 6:

• Cardiac evaluation (ECG, echocardiogram, troponin) if eosinophils ≥1.5 × 10⁹/L 6
• Pulmonary function tests to monitor for progressive bronchiectasis 1
• Consider hematology referral if eosinophilia persists >3 months despite treatment 6