PML and Sjogren syndrome: Path Explorer performed using IPA suggested that the downregulation of NF1 gene in NF1 patients may induce periodontitis via upregulation of TNF Superfamily Member 13b (TNFSF13B) while linking to sicca syndrome or Sjögren's syndrome with upregulated TNFSF13B, promyelocytic leukaemia (PML) and signal transducer and activator of transcription 1 (STAT1) (Fig. 3B).