Differential Diagnosis for Malar Rash Appearing Only in Afternoons

• Single Most Likely Diagnosis
  • Lupus Erythematosus: This condition is known for its malar rash, which can be exacerbated by sunlight. The rash typically worsens in the afternoon due to increased sun exposure throughout the day, making it a prime candidate for a diagnosis when the rash appears predominantly in the afternoons.
• Other Likely Diagnoses
  • Rosacea: This skin condition can cause a malar rash that may worsen with sun exposure, potentially appearing more pronounced in the afternoons. However, its symptoms and triggers can vary widely among individuals.
  • Seborrheic Dermatitis: While not exclusively appearing in the afternoons, seborrheic dermatitis can cause a facial rash that might seem to worsen in the afternoon due to various factors like oil production and environmental exposures.
• Do Not Miss Diagnoses
  • Sarcoidosis: Although less common, sarcoidosis can cause skin manifestations, including a malar rash. It's crucial to consider this diagnosis due to its potential for serious systemic involvement, including lung and eye complications.
  • Lymphoma: Certain types of lymphoma, like cutaneous T-cell lymphoma, can present with skin manifestations that might resemble a malar rash. Given the potential severity of lymphoma, it's essential to rule out this diagnosis.
• Rare Diagnoses
  • Pellagra: A condition caused by niacin deficiency, pellagra can lead to dermatitis, potentially manifesting as a malar rash. Its appearance might seem to correlate with afternoon sun exposure, although this is less common.
  • Erythema Multiforme: This is an immune-mediated condition that can cause target-like lesions on the skin, including the face. While it's rare and not typically confined to afternoons, its potential for severe manifestations warrants consideration in a differential diagnosis.