Regarding the investigation into SLE vs. MCTD, an initial rheumatology consultation identified a constellation of findings from the patient's medical history, along with laboratory serological markers suggestive of MCTD, including Raynaud's phenomenon, lymphopenia, possible interstitial lung disease, high-titer positive RNP, and high-titer ANA speckled 1:1280. Here, RNPC3 is linked to mixed connective tissue disease.