A validated sampling technique using tracheobronchial sampling [43,44,45,46] applied for early detection of M. hyopneumoniae in pigs [47] was used to collect samples in pigs of different age categories, with clinical signs of respiratory diseases, for subsequent analysis with a multiplex PCR (M. hyopneumoniae, PRRSV (PRRSV1, European strain; PRRSV2, North-American strain; PRRSV1,2, combined European and North-American strain), IAV-S, PCV-2, PRCV, PCMV), and a supplementary bacterial PCR (A. pleuropneumoniae), to detect seven different PRDC pathogens. The gene discussed is GREM2; the disease is respiratory system disorder.