UPDATED CLINICAL PROTOCOLS OF INHERITED FATTY ACID OXIDATION DISORDERS IN NEWBORNS: CONSOLIDATED DATA FROM THE INTERNATIONAL CLINICAL GUIDELINES
Authors: Znamenska T. , Vorobiova O. , Kuznietsov I. , Lastivka I. , Holota T. , Kremezna A. , Kryvosheieva V. , Obod M. , Samoilenko I. , Davydiuk V. , Marushko Y. , Pokhylko V. , Kirillova L. , Nikulina L. , Shveykina V. , Miroshnikov O. , Yuzva O. , Zbrozhik E. , Holiuk K. 
Published: May 2023

Fatty acid oxidation disorders (FAODs) are a group of inherited metabolic diseases (IMDs) caused by impairments in mitochondrial β-oxidation of fatty acids (FA) due to defects in genes encoding enzymes, transporters, membrane channels, and receptors that mediate this process. A common characteristic of this group of IMDs is an energy deficit associated with suppression of energy metabolism in mitochondria due to a decrease in the production of ketone bodies and the substrate of the tricarboxylic acid cycle – acetyl-coenzyme A. Since energy deficiency is a common pathogenetic factor of the entire group of FAODs, the manifestation of these inherited diseases is similar, and only certain nosologies have specific differences in the clinical picture, accordingly, these disorders require similar treatment. Initial manifestations of FAODs in neonatal and early childhood most often include cardiomyopathy, liver dysfunction, and hypoketotic hypoglycemia. For newborns with FAOD, the main danger is rapidly progressing crisis states of metabolic decompensation with severe, often fatal consequences. In adolescence, in addition to the above severe symptoms, episodes of rhabdomyolysis may also occur.Since long intervals between meals are one of the main factors provoking episodes of metabolic decompensation in patients with FAODs, the key tool for their prevention is the avoidance of prolonged fasting. In cases of the development of metabolic crisis states, symptomatic treatment is used with the introduction of carnitine according to indications. The special role of carnitine is its involvement in the transport of long-chain fatty acids through the mitochondrial membrane. Treatment of FAODs caused by a deficiency of enzymes whose substrates are long-chain fatty acids involves the use of a low-fat diet and the addition of medium-chain triglycerides and docosahexaenoic acid to the diet. Success in treating IMDs as such and FAODs, particularly, is directly related to early detection of the disease and treatment beginning since the destructive effect of toxic metabolites on internal organs and the brain increases according to the duration of exposure, leading to their progressive damage and delay in physical and mental development.An effective tool for the early detection of newborns with IMDs is the extended neonatal screening program, the implementation of which, according to the WHO, has become the greatest achievement of the health care systems of the developed countries of the world in reducing the levels of child mortality and disability in the first 10 years of the 21st century. In 2019, the program of extended newborn screening of IMDs was started in Ukraine at the initiative of the State Institution “Institute of Pediatrics, Obstetrics and Gynecology named after Academician O.M. Lukyanova of the National Academy of Medical Sciences of Ukraine”, “Association of Neonatologists of Ukraine” and “CDC Pharmbiotest” (Baby Screen, https://baby-screen.com.ua).One of the main reasons that limit the general use of this diagnostic procedure is doctors' lack of awareness and attention regarding IMDs, the causes of these serious diseases, diagnostic search algorithms, approaches to treatment, and patient follow-up. There is an urgent need for concise medical information that includes: a brief description of the individual genetic defect; characteristics of biochemical disorders and a list of marker substances that accumulate in the blood and urine of a newborn with IMDs; procedures of primary and clarifying laboratory studies; clinical manifestations of the disease; treatment strategy and prognosis. At the discretion of the Baby Screen team, this information is provided in the form of concise protocols.In this publication, we present eight Clinical Protocols, which were prepared by a team of specialists in metabolic pediatrics, medical genetics, and laboratory analytics, who were trained in the leading medical and genetic centers of the EU countries and regularly participate in training and scientific-practical seminars on this topic. The sources of information given in the protocols are international and national guidelines on extended neonatal screening, websites of leading organizations specializing in the diagnosis and treatment of IMDs, and well-known monographs and periodicals.