COL9A2 and Alzheimer disease: As part of this 7-year study (2003–2010), we screened DNA from 28 PSACH patients for mutations in COMP, 77 patients (suspected AD-MED and variants) for mutations in COMP, MATN3, and the three type IX collagen genes (COL9A1, COL9A2, and COL9A3), and 22 patients for mutations in SLC26A2 (suspected rMED).