Differential Diagnosis for the Scalp Lesion

The clinical presentation and laboratory findings suggest a fungal infection. Based on the information provided, the following differential diagnoses are considered:

• Single most likely diagnosis
  • Microsporum: The presence of numerous microconidia without macroconidia on the fungal culture is consistent with Microsporum species, which are common causes of scalp infections in children.
• Other Likely diagnoses
  • Trichophyton: Although the culture did not show macroconidia, some Trichophyton species can produce microconidia, making it a possible cause of the infection.
  • Epidermophyton: This genus can also cause fungal infections, but it is less common in scalp infections and typically does not produce microconidia.
• Do Not Miss
  • Kerion: A severe inflammatory reaction to a fungal infection, which can lead to scarring and hair loss if not treated promptly.
  • Majocchi's granuloma: A deep fungal infection that can cause granulomatous lesions, which may not respond to standard antifungal treatments.
• Rare diagnoses
  • Fusarium: A rare cause of fungal infections, which can produce microconidia, but is more commonly associated with systemic infections in immunocompromised individuals.
  • Aspergillus: Although Aspergillus can cause scalp infections, it is rare and typically occurs in immunocompromised individuals or those with underlying medical conditions.