Mitochondrial DNA Depletion Syndrome Caused by RRM2B Gene Mutation: Clinical Characteristics and Genetic Analysis of Two Cases with Different Types (8A and 8B)

RRM2B gene mutation-related diseases can be divided into four types according to genetic pattern and clinical phenotype of mitochondrial DNA depletion syndrome 8A (MTDPS8A), mitochondrial DNA depletion syndrome 8B (MTDPS8B), rod-cone dystrophy, sensorineural deafness, and fanconi-type renal dysfunction (RCDFRD), progressive external ophthalmoplegia with mitochondrial and deletions, autosomal dominant 5 (PEOA5). Among them, MTDPS8A and MTDPS8B are both mitochondrial DNA depletion syndromes with the same genetic pattern, and the clinical phenotypes are complex and heterogeneous in the early stage, making it difficult to identify them. This paper systematically reviewed and analyzed the clinical characteristics, genetic test results, diagnosis and treatment process and other case data of two children diagnosed with MTDPS8A and MTDPS8B, and reviewed relevant literature to summarize the genetic characteristics of these two types, so as to provide diagnostic ideas for future suspected cases and further improve the clinical diagnosis rate of RRM2B mutation-related mitochondrial encephalomyopathy, which also helps to assess the prognosis.