A neurodegenerative disease affecting older dogs beginning with paralysis of the pelvic limbs, that is fatal. Thankfully we have a DNA test that is approved for Pyrenean Shepherds. DNA TESTING DM – UC Davis (Listed for Pyrenean Shepherds) Research & Articles What is Degenerative Myelopathy? (University of MO) – Degenerative myelopathy (DM) is a fatal neurodegenerative disease that affects older dogs. It initially results in paralysis of the pelvic limbs but progresses to affect all limbs.