This 7th edition is a milestone in the series of Inborn Metabolic Diseases (IMD), recognised as the standard textbook for professionals involved in the diagnosis and management of IMD. Within the last 5 years a Copernican revolution in our understanding of IMD has changed the definition, concepts, paradigms, and classification. This new edition now extends the concept of IMD to include those disturbances in molecular machinery diagnosed by molecular techniques but currently without measurable metabolic markers. The book presents a clinical and biochemical approach to the diagnosis and management of IEM with many diagnostic algorithms for patients of all ages and with a particular focus on neurological presentations. It includes separate, comprehensive sections on IEM classified in 3 major pathophysiological categories: disorders of energy metabolism, both mitochondrial and non-mitochondrial; small molecule disorders, mostly diagnosed with metabolic markers; and complex molecules disorders, mostly diagnosed with molecular techniques. Two new chapters were added, describing around 600 disorders of nucleic acid metabolism, tRNA metabolism, ribosomal biogenesis, and cellular trafficking.