The first course recalls the basics of genetics, mutations and their consequences and the modes of transmission of genetic characters: dominant, recessive, sex-linked and mitochondrial. In subsequent courses, the major groups of inborn errors of metabolism will be studied by metabolism: amino acids, carbohydrates, lipids, purines and pyrimidines, porphyria, neurotransmitters. Diseases affecting intracellular organelles, mitochondria, peroxisomes and lysosomes are also described, as are congenital glycosylation defects. Each group of diseases is approached by relating the biochemical pathways concerned, with the clinical and biological presentations, the physiopathological mechanisms, the diagnostic approach, the treatment, the prognosis and the genetic abnormalities. In the last two courses, metabolic diseases are reviewed from the study of the differential diagnosis of clinical and laboratory presentations.