FGF21 and nutritional deficiency disease: Moreover, a recently published study analyzed subphenotypes of frailty in lung transplant candidates and found that subfenotype 2, characterized by systemic and innate inflammation (higher PTX3 as well as IL-6, CRP, TNF-R1, and IL-1RA), mitochondrial stress (higher GDF-15 and FGF-21), sarcopenia, malnutrition, and lower hemoglobin and walk distance, had a higher level of disability and higher risk of waitlist delisting or death [36].