Non syndromic childhood onset congenital sideroblastic anemia: A report of 13 patients identified with an ALAS2 or SLC25A38 mutation.

The most frequent germline mutations responsible for non syndromic congenital sideroblastic anemia are identified in ALAS2 and SLC25A38 genes. Iron overload is a key issue and optimal chelation therapy should be used to limit its adverse effects on the development of children. Our multicentre retrospective descriptive study compared the strategies for diagnosis and management of congenital sideroblastic anemia during the follow-up of six patients with an ALAS2 mutation and seven patients with an SLC25A38 mutation. We described in depth the clinical, biological and radiological phenotype of these patients at diagnosis and during follow-up and highlighted our results with a review of available evidence and data on the management strategies for congenital sideroblastic anemia. This report confirms the considerable variability in manifestations among patients with ALAS2 or SLC25A38 mutations and draws attention to differences in the assessment and the monitoring of iron overload and its complications. The use of an international registry would certainly help defining recommendations for the management of these rare disorders to improve patient outcome.

Sideroblastic anemia: molecular analysis of the ALAS2 gene in a series of 29 probands and functional studies of 10 missense mutations.

X-linked Sideroblastic Anemia (XLSA) is the most common genetic form of sideroblastic anemia, a heterogeneous group of disorders characterized by iron deposits in the mitochondria of erythroid precursors. XLSA is due to mutations in the erythroid-specific 5-aminolevulinate synthase (ALAS2) gene. Thirteen different ALAS2 mutations were identified in 16 out of 29 probands with sideroblastic anemia. One third of the patients were females with a highly skewed X-chromosome inactivation. The identification of seven novel mutations in the ALAS2 gene, six missense mutations, and one deletion in the proximal promoter extends the allelic heterogeneity of XSLA. Most of the missense mutations were predicted to be deleterious, and 10 of them, without any published functional characterization, were expressed in Escherichia coli. ALAS2 activities were assayed in vitro. Five missense mutations resulted in decreased enzymatic activity under standard conditions, and two other mutated proteins had decreased activity when assayed in the absence of exogenous pyridoxal phosphate and increased thermosensitivity. Although most amino acid substitutions result in a clearly decreased enzymatic activity in vitro, a few mutations have a more subtle effect on the protein that is only revealed by in vitro tests under specific conditions.