Differential Diagnosis for Scarring, Depigmented Scalp Lesions

Single Most Likely Diagnosis

• Discoid Lupus Erythematosus (DLE): Given the patient's history of SLE and DLE, DLE is a common cause of scarring, depigmented scalp lesions. It is characterized by chronic, inflammatory, and scarring skin lesions, often on the scalp, face, and ears.

Other Likely Diagnoses

• Lichen Planopilaris: An inflammatory condition that causes scarring hair loss, often accompanied by depigmentation. It can present similarly to DLE but lacks the systemic symptoms.
• Alopecia Areata: Although typically non-scarring, some forms like alopecia areata monolocularis can cause scarring and depigmentation, especially if there's a significant inflammatory component.
• Sarcoidosis: Can cause scarring alopecia and depigmentation, particularly in the context of systemic disease.

Do Not Miss Diagnoses

• Malignancy (e.g., Cutaneous T-Cell Lymphoma): Although less common, malignancies can cause scarring, depigmented lesions on the scalp. Early diagnosis is crucial for treatment and prognosis.
• Infections (e.g., Fungal, Bacterial): Certain infections can cause scarring and depigmentation, especially if not treated promptly. Fungal infections like favus can lead to scarring alopecia.

Rare Diagnoses

• Congenital Aplasia Cutis: A rare condition where there's a absence of skin in a localized or widespread area, sometimes involving the scalp. It can be mistaken for scarring from other causes.
• Pseudopelade of Brocq: A rare, chronic, and scarring form of alopecia that can cause depigmented patches on the scalp, often without significant inflammation.
• Follicular Degeneration Syndrome: A condition that primarily affects African American women, leading to scarring hair loss and can be associated with depigmentation.

Congenital Scalp Affections

• Neurocutaneous Syndromes: Certain syndromes like tuberous sclerosis can cause congenital scalp lesions that might appear as scarring or depigmented areas.
• Aplasia Cutis Congenita with Epidermal and Dermal Abnormalities: Though rare, these conditions can present with scalp defects at birth, which might resemble scarring or depigmented lesions later in life.

Each of these diagnoses requires careful consideration of the patient's history, clinical presentation, and possibly further diagnostic testing to determine the underlying cause of the scarring, depigmented scalp lesions.