Pityriasis%20(tinea)%20versicolor Diagnosis

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

• 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