Differential Diagnosis for the Pediatric Patient
The patient's presentation of multiple annular plaques with central clearing, raised scaly borders, and evidence of secondary impetiginization, following a flare of atopic dermatitis treated with a medium-potency topical corticosteroid, suggests several potential diagnoses. These can be categorized as follows:
- Single Most Likely Diagnosis
- Tinea Corporis (Ringworm): This is the most likely diagnosis given the annular plaques with central clearing and raised, scaly borders. The presence of peripheral scaling, crusting, erythema, and excoriations, along with the well-demarcated and superficial nature of the lesions, are all consistent with tinea corporis. The history of atopic dermatitis and recent use of topical corticosteroids, which can sometimes exacerbate fungal infections, further supports this diagnosis.
- Other Likely Diagnoses
- Nummular Dermatitis: Characterized by coin-shaped patches of eczema, nummular dermatitis could be considered, especially given the patient's history of atopic dermatitis. However, the central clearing and annular shape of the lesions are more suggestive of a fungal etiology.
- Contact Dermatitis: An allergic or irritant reaction could present with similar lesions, but the pattern and description are less typical for contact dermatitis, which usually doesn't have such a distinct annular shape with central clearing.
- Psoriasis: Although less common in children, psoriasis can present with annular plaques. However, the presence of significant pruritus and the context of atopic dermatitis make this less likely.
- Do Not Miss Diagnoses
- Cellulitis: While the lesions appear superficial, any sign of deeper tissue involvement, such as increased warmth, swelling, or systemic symptoms, would necessitate consideration of cellulitis, a bacterial infection of the skin and subcutaneous tissues. The presence of honey-colored crusts indicating secondary impetiginization already points to a bacterial component, but cellulitis would require more urgent treatment.
- Eczema Herpeticum: A serious complication of atopic dermatitis, eczema herpeticum is caused by a disseminated herpes simplex virus infection within the skin. It presents with painful, punched-out erosions, and although the current description doesn't perfectly match, any sign of herpetic lesions in a patient with atopic dermatitis warrants immediate attention.
- Rare Diagnoses
- Granuloma Annulare: A benign condition characterized by circular lesions composed of small bumps, granuloma annulare is less common and typically doesn't have the same level of scaling or pruritus as seen in this patient.
- Annular Lichen Planus: Although lichen planus can present with annular lesions, it is less common in children and typically has a distinct violaceous color and polygonal papules, which are not described in this case.
Each of these diagnoses should be considered in the context of the patient's history, physical examination, and response to previous treatments. Diagnostic tests, such as a potassium hydroxide (KOH) preparation to confirm fungal elements or bacterial cultures to identify secondary impetiginization, may be necessary to solidify the diagnosis and guide appropriate treatment.