Pityriasis%20(tinea)%20versicolor Diagnosis
Assessment
Considerations for a Dermatology referral:
- Negative microscopy and unclear diagnosis
- Extensive and severe infection
- Treatment failure in primary care setting
- Consideration of oral antifungal therapy in children <12 years old
- Immunocompromised patients
- Consideration of long-term antifungal prophylaxis
Laboratory Tests
- Lab testing is not usually needed for the diagnosis
- Consider doing microscopy if:
- Diagnosis is unclear
- Infection is unresponsive to the regular topical antifungals
- Planning oral antifungal treatment
Microscopy
- Potassium hydroxide (KOH) examination of skin scrapings should confirm the diagnosis
- Scales or debris are examined under light microscope after adding a drop of 10-20% KOH solution
- Short stubby hyphae and yeast cells will appear as the typical “spaghetti and meatballs” appearance
- Calcofluor may be used but this technique requires utilization of fluorescence microscope
- Malassezia species also stain well with periodic acid-schiff (PAS) or methenamine silver
Culture
- Unnecessary for routine diagnosis
- Difficult to grow Malassezia in standard mycological media
Wood’s Light Exam
- May be used to detect subclinical lesions
- However, yellowish to white fluorescence is indicative only in approximately 1/3 of cases