Differential Diagnosis for Pruritic, Scaling Areas of Hair Loss

Single Most Likely Diagnosis

• Tinea capitis: This is a fungal infection of the scalp, which is common in children and adolescents. The presentation of pruritic, scaling areas of hair loss with scaly patches and alopecia is consistent with this diagnosis. The treatment typically involves oral antifungals.

Other Likely Diagnoses

• Seborrheic dermatitis: This condition can cause scaly patches and hair loss, especially in areas with high sebaceous gland activity like the scalp. It is often accompanied by itching and can be treated with topical corticosteroids or antifungals.
• Psoriasis: Although less common on the scalp in the absence of other body involvement, psoriasis can cause scaly, pruritic plaques that lead to hair loss. Treatment often involves topical corticosteroids.
• Eczema (atopic dermatitis): This can also present with pruritic, scaly patches, although it's less commonly associated with distinct areas of alopecia. Treatment typically includes topical corticosteroids and moisturizers.

Do Not Miss Diagnoses

• Alopecia areata: An autoimmune condition leading to hair loss, which can sometimes be accompanied by scaling if there is a secondary infection. It's crucial to diagnose as it may require different management, including topical corticosteroids or immunotherapy.
• Syphilis (secondary): This can cause a variety of skin manifestations, including alopecia and scaling. Given the potential severity of untreated syphilis, it's a critical diagnosis not to miss. Treatment involves antibiotics.

Rare Diagnoses

• Kerion: A severe form of tinea capitis that can cause significant inflammation, pus, and scarring alopecia. It requires prompt treatment with oral antifungals.
• Discoid lupus erythematosus: An autoimmune condition that can cause scarring alopecia with scaling. It's less common and requires specific treatment, often involving topical or systemic corticosteroids and other immunosuppressants.
• Lichen planopilaris: An inflammatory condition that leads to scarring alopecia, which can be accompanied by scaling. Treatment may involve topical corticosteroids, oral antifungals, or other immunosuppressive agents.

Given the information provided, the most appropriate initial treatment without further diagnostic workup (like fungal culture or biopsy) would lean towards b. Prescribe a topical antifungal for a presumed diagnosis of tinea capitis or seborrheic dermatitis, considering the commonality of these conditions in the described demographic and presentation. However, a definitive diagnosis through further examination or diagnostic tests is crucial for targeted treatment.