Differential Diagnosis

The patient's symptoms of burning, redness, and hair shedding localized to the back of the head and crown area, along with a positive scalp KOH prep, suggest a fungal infection. The lack of improvement with fluconazole and the request for terbinafine indicate a possible dermatophyte infection. Here are the differential diagnoses categorized:

• Single most likely diagnosis
  • Tinea capitis (Dermatophyte infection): The positive KOH prep and the patient's symptoms are consistent with a dermatophyte infection, which is commonly treated with terbinafine. The lack of response to fluconazole, which is more effective against yeast infections, further supports this diagnosis.
• Other Likely diagnoses
  • Candidiasis: Although the patient did not respond to fluconazole, candidiasis is still a possibility, especially if the strain is resistant to fluconazole. However, the presentation is less typical for candidiasis.
  • Seborrheic dermatitis: This condition can cause redness and hair shedding, but the positive KOH prep and the specific localization to the back of the head and crown area make it less likely.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Kerion: A severe form of tinea capitis that can cause significant inflammation and scarring. It requires prompt treatment to prevent long-term hair loss.
  • Majocchi's granuloma: A deep dermatophyte infection that can cause granulomatous lesions. It is less common but can be severe if left untreated.
• Rare diagnoses
  • Fungal folliculitis: An infection of the hair follicles caused by fungi, which can present with similar symptoms.
  • White piedra: A superficial fungal infection of the hair shaft, which can cause hair shedding and redness. However, it is less common and typically does not cause burning sensations.