In general, aplastic anemia refers to acquired reoccurrence, therefore the diagnosis of reoccurrence must exclude congenital reoccurrence, especially in children and young adults. The treatment strategies, therapeutic approaches and prognosis of acquired and congenital remitting disorders are significantly different, while the clinical differentiation of the two is sometimes exceptionally difficult. Congenital remitting disorders are a rare group of genetically heterogeneous disorders characterized by bone marrow hematopoietic failure, congenital somatic anomalies and tumor susceptibility, mainly seen in fanconi anaemia (FA) and dyskeratosis congenita (DC).FA is an autosomal or X-linked recessive disorder FA is an autosomal or X-linked recessive disorder with progressive onset at birth or early childhood, with one or more lines of hemocytopenia, with somatic or visceral malformations, mental retardation, and early development of solid tumors. The typical patient is not easily missed, but approximately 20% of FA patients may not have these abnormalities, and some patients may not start to develop hematologic changes until adulthood (the highest age of onset has been reported to be 49 years), making them easy to miss and misdiagnose. Therefore, the 2009 edition of the UK guidelines for the diagnosis and treatment of reoccurrence recommends that all children and young adults with reoccurrence should be routinely screened for FA, and the upper age limit for screening has been revised upwards from 35 years to 50 years. Cells from FA patients show spontaneous chromosome breaks and are highly sensitive to DNA cross-linking agents such as diepoxybutane (DEB) and mitomycin (MMC). Peripheral blood lymphocytes from FA patients treated with DEB and MMC have significantly more chromosome breaks and are the current gold standard for the diagnosis of FA. Chromosome breakage test can be used for peripheral blood or bone marrow cells, amniocytes, chorionic villous cells, fetal blood cells and skin fibroblasts. For patients with normal lymphocyte DEB test or MMC test and high clinical suspicion of FA, further fibroblast DEB test or MMC test should be performed to exclude false negative lymphocyte DEB test due to FA cell mutations that cause somatic cells to return to normal. Therefore, the use of flow cytometry to detect the peripheral blood cell cycle is also relevant for the diagnosis of FA. The comet test is a single-cell gel electrophoresis for rapid detection of DNA damage, and can also be used for the detection of FA patients and carriers. In recent years, gene mutation detection has also been used for FA diagnosis and typing. 16 known pathogenic genes (FANCA, B, C, D1, D2, E, F, G, I, J, L, M, N, O, P and Q) have been identified, and 16 corresponding FA disease types exist. At present, most of the clinics use the first generation sequencing technology, which is expensive and difficult to be widely applied. The combination with gene sequencing can make a more comprehensive diagnosis of FA, especially for patients with atypical clinical manifestations but suspected FA, but at present, this test is mostly used for experimental research in China. Typical DC patients often show the triad of signs, toe (finger) nail dyskeratosis, skin pigmentation and oral mucosa leukoplakia, which is easier to diagnose, while patients who show hematopoietic failure without obvious physical abnormalities are more difficult to diagnose. The detection of telomere length of various subpopulations of peripheral blood leukocytes (total lymphocytes, CD45RA+/CD20-naive T cells, CD20+ B cells) by flow fluorescence in situ hybridization is currently the best diagnostic method, with high sensitivity and specificity, and can be used to differentiate from other bone marrow hematopoietic failures. In addition, there are eight genes that have been shown to cause DC: CTC1, DKC1, TERC, TERT, TINF2, WRAP53, NHP2 and NOP10, which are inherited in three ways: X-linked recessive, autosomal recessive and autosomal dominant. Mutation detection of these genes is also useful for the diagnosis of DC. About 30% of DC patients are affected by mutations in DKC1, an X-linked recessive gene that encodes the protein dyskeratine, an important component of telomerase activity, and DKCl mutations have been shown to cause a decrease in telomerase RNA levels and a significant shortening of telomere length. Since leukocyte telomere length testing and DC-related gene mutation testing are not currently performed as routine clinical tests in most units, it is recommended that this test be performed at least in patients who have failed immunosuppressive therapy to help clarify the diagnosis and adjust the treatment plan.