Microcytic anemia is often due to disorder of globin genes. Here, we focus on rare monogenic microcytic anemias, We describe the diferent congenital forms that are due to mutations in genes implicated in iron homeostasis, the heme biosynthesis pathway, the cluster Fe-S biosynthesis pathway andmitochondrial proteins biosynthesis pathway. Among rare congenital microcytic anemias, most frequent forms are non syndromic sideroblastic anemias and iron refractory iron deficiency anemias (IRIDA). Sideroblastic anemias is characterized by mitochondrial iron overload and presence of ring sideroblasts in patient bone marrow.. IRIDA results from bi-allelic mutations of TMPRSS6 gene encoding Matriptase-2. Matriptase-2 protein is a transmembrane serine protease that plays an essential role in down-regulating hepcidin, the key regulator of iron homeostasis. The next generation sequencing would be helpful to identify the genes implicated in unexplained rare anemias.