Differential Diagnosis for Annular Fungal Skin Lesion

• Single Most Likely Diagnosis
  • Tinea corporis (Ringworm): This is the most common cause of annular fungal skin lesions. It is a superficial fungal infection that can affect any part of the body and is characterized by a circular, itchy, and red rash with a clear center.
• Other Likely Diagnoses
  • Tinea cruris (Jock itch): A fungal infection of the groin area, which can also present with annular lesions.
  • Candidiasis: A fungal infection caused by Candida species, which can cause annular lesions, especially in moist areas of the body.
  • Dermatophytid reaction: An immune response to a fungal infection elsewhere on the body, which can cause annular lesions.
• Do Not Miss Diagnoses
  • Lyme disease: Caused by the bacterium Borrelia burgdorferi, transmitted by ticks. It can cause an annular rash known as erythema migrans, which is a critical diagnosis to make due to the potential for serious complications if left untreated.
  • Erythema chronicum migrans: A condition that can mimic fungal infections but is actually a manifestation of an underlying disease such as Lyme disease or another tick-borne illness.
• Rare Diagnoses
  • Granuloma annulare: A benign skin condition characterized by small, circular bumps that can form rings, although it is not typically considered a fungal infection.
  • Annular lichen planus: A rare variant of lichen planus that can present with annular lesions, which is an autoimmune condition rather than a fungal infection.
  • Subcutaneous mycoses: Rare fungal infections that involve the subcutaneous tissue, such as sporotrichosis, which can cause nodular or ulcerative lesions that may appear annular.