[Aldehyde degradation deficiency (ADD) syndrome: discovery of a novel fanconi anemia-like inherited BMF syndrome due to combined ADH5/ALDH2 deficiency]

We have recently described the identification of a novel inherited bone marrow failure syndrome. The first set of patients was diagnosed through the exome analysis of cells from Japanese patients with hypoplastic anemia, which have been deposited to the JCRB cell bank for quite some time previously. Originally, these cases were diagnosed with a novel disorder based on increased levels of sister chromatid exchanges in lymphocytes; however, causative genes were clarified only after applying the recently developed next-generation sequencing technology. Aldehyde degradation deficiency syndrome (ADDS) is caused by combined defects in two genes, ADH5 and ALDH2, which are both critical for degrading endogenously generated formaldehyde. Formaldehyde is highly reactive and toxic to biological molecules including DNA, and its endogenous generation in the absence of the degradation system results in DNA damage that overwhelms the DNA repair capacity, leading to the development of BMF with loss of hematopoietic stem cells and progression to MDS/leukemia. In this short review, we would like to summarize what is known today about ADDS for a wide readership of hematology clinicians in Japan.