This article discusses the identification of a novel frameshift mutation in the cathepsin C gene in a patient with coexisting Papillon-Lefevre syndrome (PLS) and rheumatoid arthritis (RA). PLS is a rare autosomal recessive disorder characterized by palmoplantar keratoderma and severe periodontitis, while RA is an inflammatory joint disease. The patient, a Taiwanese individual, exhibited dental and cutaneous features consistent with PLS and was later diagnosed with RA. Genetic testing revealed a homozygous frameshift mutation in the cathepsin C gene. The coexistence of PLS and RA in this patient is unique and suggests a complex relationship between the two conditions. Further research is needed to understand the pathogenic link between PLS and RA. [Extracted from the article]