Differential Diagnosis for Ringworm-like Lesion in the Armpit
The patient presents with a ring-shaped lesion in the left armpit, which has been persistent for over a month, is itchy, and has shown some growth. Based on the description, the following differential diagnoses are considered:
- Single most likely diagnosis
- Tinea corporis (ringworm): This is the most likely diagnosis given the classic ring-shaped appearance of the lesion with a clear center. The location in the armpit, although less common, can occur due to the warm and moist environment that fosters fungal growth.
- Other Likely diagnoses
- Contact dermatitis: This could be due to an allergic reaction or irritant in the armpit area, leading to a rash that might resemble ringworm. The itchiness supports this possibility.
- Eczema (atopic dermatitis): Eczema can cause itchy, inflamed skin that might appear in a ring-like pattern, especially in areas like the armpits where skin folds can create a warm, moist environment.
- Intertrigo: A skin condition that occurs due to friction in skin folds, often accompanied by a fungal or bacterial infection, which could present with a ring-like appearance and itchiness.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Cutaneous lymphoma: Although rare, cutaneous lymphomas can present with skin lesions that might resemble ringworm. Missing this diagnosis could have severe consequences.
- Invasive fungal infections: In immunocompromised patients, fungal infections can be more aggressive and life-threatening. A lesion that does not respond to typical antifungal treatments could indicate a more serious condition.
- Rare diagnoses
- Granuloma annulare: A benign skin condition that can cause ring-shaped lesions, although it's less common in the armpit area and typically not itchy.
- Erythema migrans (Lyme disease): Although the classic presentation is on the trunk or limbs, an early sign of Lyme disease could theoretically appear in any location, including the armpit, as a expanding ring-like rash.
- Mycosis fungoides: A rare type of cutaneous T-cell lymphoma that can present with various skin lesions, including those resembling ringworm, especially in its early stages.