We were able to develop an endophenotypic class of severe Long COVID with very low SpO2 during acute infection, and Long COVID biomarkers including low tryptophan, and elevated kynurenine, KYN/TRY ratio, CRP, and a very high score on physiosomatic, Fibro-Fatigue, depression and anxiety symptom domains. The gene discussed is CRP; the disease is major depressive disorder.