C1S and Ehlers-Danlos syndrome: We previously identified heterozygous missense mutations in the C1R and C1S genes in patients affected by periodontal EDS (pEDS, OMIM 130080 and 617174) (2), a rare specific EDS subtype hallmarked by early severe periodontitis leading to premature loss of teeth (3), in addition to connective tissue alterations (4).