MMP9 and peptic ulcer disease: Data on the allele and genotype frequencies of the three functionally significant single nucleotide polymorphisms (SNPs) of the matrix metalloproteinases (MMP) genes (rs1799750 MMP1, rs3918242 and rs17576 MMP9) in Russian patients with primary open-angle glaucoma (POAG), essential hypertension (EH) and peptic ulcer (PU) are presented.