<p>TNF is a central regulator of immune responses, inflammation and programmed cell death, and has an essential role in maintaining tissue and immune homeostasis. Abnormal TNF signalling is implicated in a broad spectrum of physiological and pathological processes, as exemplified by monogenic disorders arising from dysregulation of core components of the TNF pathway. These rare conditions encompass various autoinflammatory syndromes, immunodeficiencies, autoimmune diseases and neurodegenerative conditions, and offer unique insights into the molecular mechanisms driving pathology via TNF-mediated inflammation and cell death. Collectively, these diseases underscore the importance of tightly regulated TNF signalling for immune balance and illustrate how distinct molecular defects can produce overlapping clinical phenotypes. Variability in pathway integration and tissue-specific gene expression further shapes disease presentation, whereas disruption of post-translational modifications and cell-death regulators have emerged as central pathogenic mechanisms. Together, these insights highlight the need for precise genetic and mechanistic understanding to inform diagnosis and therapeutic strategies.</p>