A 28-year-old woman with a 6-month history of photosensitive facial erythema presents to the dermatology clinic. Examination reveals a symmetric erythematous rash over the cheeks and bridge of the nose in a butterfly distribution. The area marked **C** in the diagram (nasolabial folds) is notably spared. Laboratory investigations show ANA 1:320, anti-dsDNA positive, and low C3 levels. Which of the following diagnoses is most strongly supported by the sparing of the nasolabial folds as a distinguishing feature?