MMP9 and Alzheimer disease: A mucin-like glycoprotein called endogenous proteoglycan 4 (PRG4) in saliva samples was observed at elevated levels in SS patients, improving the understanding of the disease growth and treatment.183 Grant et al. have found that the best performing panels, including MMP9, S100A8, alpha-1-acid glycoprotein, and pyruvate kinase, could distinguish between periodontal health and disease states.184 In Alzheimer’s disease (AD), whether salivary lactoferrin could be the candidate biomarker reached inconsistent conclusions.