PDGFRB and systemic sclerosis: Other antibodies that have been observed in SSc with conflicting or minimal data regarding association with SSc-ILD include antibodies to platelet derived growth factor receptor (PDGFR), endothelial cells, activating transcription factor-2 (ATF-2), peroxiredoxin I (Prx I) and B23/nucleophosmin/numatrin [55,78,79,80,81].