Differential Diagnosis for Ringworm

• Single most likely diagnosis
  • Tinea corporis (ringworm): This is the most likely diagnosis due to the characteristic ring-shaped lesions and the common occurrence of this fungal infection in the general population.
• Other Likely diagnoses
  • Nummular eczema: This condition can present with coin-shaped patches of eczema that may resemble ringworm, especially if the patient has a history of atopic dermatitis.
  • Psoriasis: Plaque psoriasis can sometimes present with annular (ring-shaped) lesions, although they typically have a thicker, more scaly appearance than ringworm.
  • Seborrheic dermatitis: While typically found on the scalp, face, and torso, seborrheic dermatitis can occasionally present with ring-shaped lesions, particularly in immunocompromised patients.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed)
  • Erythema migrans (Lyme disease): Although less common, erythema migrans can present with a ring-shaped rash, and missing this diagnosis could lead to untreated Lyme disease, which can have serious long-term consequences.
  • Leprosy: In rare cases, leprosy can present with ring-shaped skin lesions, and missing this diagnosis could lead to significant morbidity if left untreated.
• Rare diagnoses
  • Granuloma annulare: A benign skin condition that can present with ring-shaped lesions, although it is less common and typically has a distinctive appearance with papules at the edge of the ring.
  • Subcutaneous zygomycosis: A rare fungal infection that can present with ring-shaped lesions, typically in immunocompromised patients, and requires prompt treatment to prevent serious complications.