Pharmacotherapy is a key component of anesthesiology and intensive care medicine. The individual genetic profile influences not only the effect of pharmaceuticals but can also completely alter the mode of action. New technologies for genetic screening (e.g. next generation sequencing) and increasing knowledge of molecular pathways foster the disclosure of pharmacogenetic syndromes, which are classified as rare diseases. Taking into account the high genetic variability in humans and over 8000 known rare diseases, up to 20 % of the population may be affected. In summary, rare diseases are not rare. Most pharmacogenetic syndromes lead to a weakening or loss of pharmacological action. In contrast, malignant hyperthermia (MH), which is the most relevant pharmacogenetic syndrome for anesthesia, is characterized by a pharmacologically induced overactivation of calcium metabolism in skeletal muscle. Volatile anesthetic agents and succinylcholine trigger life-threatening hypermetabolic crises. Emergency treatment is based on inhibition of the calcium release channel of the sarcoplasmic reticulum by dantrolene. After an adverse pharmacological event patients must be informed and a clarification consultation must be carried out during which the hereditory character of MH is explained. The patient should be referred to a specialist MH center where a predisposition can be diagnosed by the functional in vitro contracture test from a muscle biopsy. Additional molecular genetic investigations can yield mutations in the genes for calcium-regulating proteins in skeletal muscle, e.g. ryanodine receptor 1 (RyR1) and calcium voltage-gated channel subunit alpha 1S (CACNA1S). Currently, an association to MH has only been shown for 35 mutations out of more than 400 known and probably hundreds of unknown genetic variations. Furthermore, MH predisposition is not excluded by negative mutation screening. For anesthesiological patient safety it is crucial to identify individuals at risk and warn genetic relatives; however, the legal requirements of the Patients Rights Act and the Human Genetic Examination Act must be strictly adhered to. Specific features of insurance and employment law must be respected under consideration of the Human Genetic Examination Act.