A multimorbidity phenotype is observed after genetic knockout of mitochondrial transcription factor A (Tfam) in T cells with reduced life expectancy, systemic dysfunction and immune incompetency in mice (Desdín-Micó et al, 2020), highlighting that impaired function of T cells alone could predispose older organism to infections, cancer progression or accumulation of senescent cells (Desdín-Micó et al, 2020; Escrig-Larena et al, 2023) (Fig. 1). The gene discussed is TFAM; the disease is infection.