The pivotal role of MSTN in the development of RA is widely acknowledged in the scientific literature [90,346,347,396,397,398,399], as it upregulates TNFα and IL-1β expression through the PI3K-Akt signalling pathway in FLS, promoting muscle atrophy and osteoclast differentiation [396]. The gene discussed is MSTN; the disease is rheumatoid arthritis.