COL9A2 encodes the α2 chain of type IX collagen, a structural component of hyaline cartilage and the vitreous of the eye that contributes to extracellular matrix tensile strength 1. The gene consists of 32 exons spanning approximately 15 kb 2. COL9A2 is extensively expressed in intervertebral disc tissue, where it plays a critical role in maintaining cartilage integrity 3. Col9a2 gene deletion in mice accelerates intervertebral disc degeneration through multiple mechanisms: increased endplate porosity and osteochondral remodeling, suppressed extracellular matrix synthesis (decreased Col2a1 and Aggrecan expression), and enhanced matrix degradation with increased Mmp13 and chondrocyte hypertrophy markers 4. Pathogenic variants in COL9A2 are associated with recessive Stickler syndrome, characterized by high myopia (near-universal), sensorineural hearing loss, and retinal detachment risk 5. COL9A2 mutations also cause multiple epiphyseal dysplasia with early-onset osteoarthritis and progressive muscular atrophy 6. However, common COL9A2 polymorphisms (rs12077871, rs12722877, rs7533552) show no significant association with lumbar disc disease susceptibility in meta-analysis 1. Patients with collagen gene mutations including COL9A2 present with growth retardation and skeletal abnormalities responsive to recombinant human growth hormone therapy 7.