This has helped identify candidate biomarkers for diseases like ALS and PD, such as changes in the levels of chromogranin B, UCHL1, GPNMB, and cathepsin D. In summary, the identification and differentiation of co-pathologies through specific biomarker profiles is an emerging area of interest in the field of biomedical research. The gene discussed is GPNMB; the disease is Parkinson disease.