What is the appropriate diagnostic workup and management for a 13-year-old female presenting with a two‑week non‑productive cough, weakness, and dorsal finger lesions that could represent a fungal infection or allergic contact dermatitis?

Diagnostic Workup and Management

This presentation of non-productive cough, weakness, and dorsal finger lesions in a 13-year-old female requires immediate evaluation for systemic fungal infection, particularly invasive aspergillosis, which can present with these exact features and carries significant mortality risk if diagnosis is delayed.

Initial Assessment Priority

The combination of respiratory symptoms with skin lesions and constitutional symptoms (weakness) raises concern for a systemic process rather than isolated dermatologic or respiratory conditions. While the cough duration of 2 weeks doesn't yet meet the chronic cough threshold (>4 weeks) defined in pediatric guidelines 1, the presence of skin lesions and weakness suggests a more urgent systemic evaluation is warranted.

Critical Red Flags to Assess Immediately:

• Immunocompromised state: Any history of recurrent infections, underlying conditions, or medication use
• Eosinophilia: Can indicate fungal sensitization or infection 2
• Fever pattern: Even low-grade fevers with respiratory symptoms warrant fungal consideration 2
• Progressive weakness: Suggests systemic involvement beyond localized infection

Diagnostic Workup Algorithm

First-Line Investigations:

1. Complete blood count with differential

   • Look specifically for eosinophilia, which has been associated with invasive aspergillosis even in immunocompetent patients 2
   • Assess for leukocytosis or immunosuppression markers

2. Chest imaging (X-ray initially, CT if abnormal)

   • Upper lobe consolidation or mediastinal involvement suggests fungal etiology 2
   • Even immunocompetent adolescents can develop invasive pulmonary aspergillosis 2

3. Inflammatory markers

   • CRP and procalcitonin (procalcitonin <1 ng/mL with elevated CRP suggests fungal over bacterial infection) 3

4. Skin lesion evaluation

   • Potassium hydroxide (KOH) preparation of skin scrapings from finger lesions
   • Fungal culture from skin lesions
   • Consider skin biopsy if initial tests negative but suspicion remains high

Second-Line Investigations (if initial workup suggests fungal infection):

1. Aspergillus-specific testing

   • Serum galactomannan antigen
   • Aspergillus PCR from blood 3
   • Beta-D-glucan (though less specific)

2. Respiratory sampling

   • Induced sputum for fungal culture and PCR
   • Bronchoalveolar lavage (BAL) with Aspergillus DNA detection if imaging abnormal 3
   • Look for basidiomycetous fungi, which can cause chronic cough with fungal colonization 4

3. Contact dermatitis evaluation (if fungal workup negative)

   • Detailed exposure history: cosmetics, personal care products, topical medications, clothing, gloves 5
   • Occupational/recreational exposures 5
   • Consider patch testing only after acute phase resolves 5

Management Approach

If Fungal Infection Suspected or Confirmed:

Initiate antifungal therapy immediately without waiting for culture confirmation if clinical suspicion is high, as delayed treatment significantly increases mortality 2.

• First-line: Voriconazole (preferred for aspergillosis in adolescents)
• Alternative: Liposomal amphotericin B if severe presentation 6
• Consider adding caspofungin if inadequate response to amphotericin B alone 3

Critical caveat: A case report demonstrated fatal outcome in an 18-year-old immunocompetent female with invasive aspergillosis despite amphotericin B therapy started one day before death, emphasizing the importance of early recognition 2.

If Contact Dermatitis More Likely:

Only pursue this diagnosis after excluding systemic fungal infection, given the higher morbidity/mortality risk of missed fungal disease.

• Allergen/irritant avoidance is paramount 5
• Topical corticosteroids for skin lesions 7
• Emollients for barrier restoration 7
• Address any wash products containing harsh surfactants that damage skin barrier 5

Common Pitfalls to Avoid

1. Assuming immunocompetence excludes invasive fungal infection: Multiple case reports demonstrate invasive aspergillosis in immunocompetent adolescents 2, 6

2. Waiting for chronic cough criteria (>4 weeks) before investigating: The presence of systemic symptoms and skin lesions mandates earlier investigation 1

3. Attributing all symptoms to contact dermatitis: The combination of respiratory and dermatologic symptoms with weakness suggests systemic disease

4. Delaying antifungal therapy pending culture results: If clinical suspicion is high, empiric therapy should begin immediately 2

5. Missing underlying immunodeficiency: Diagnosis of invasive fungal infection should prompt evaluation for conditions like chronic granulomatous disease 6

Specific Concerns to Address in History

• Atopic history: Personal or family history of atopy, asthma, hay fever 5
• Environmental exposures: Wood decay fungi (Bjerkandera adusta), mushroom spores 4
• Product exposures: Nickel, fragrances, cobalt in jewelry or clothing 5
• Geographic exposures: Endemic fungal infections (though less likely with finger lesions)

The threshold for fungal investigation should be low in this presentation, as the mortality risk of missed invasive aspergillosis far outweighs the risks of diagnostic workup and empiric antifungal therapy.