CDAN1 (codanin 1) is an essential ubiquitous protein whose mutations cause congenital dyserythropoietic anemia type 1 (CDA1), a rare autosomal recessive disorder affecting erythroid development 1. The primary function of CDAN1 involves regulating histone chaperone activity through direct interaction with ASF1A and ASF1B proteins 1. Structurally, CDAN1 dimerizes and assembles into cytosolic complexes where it sequesters ASF1 molecules by occupying all functional binding sites required for histone chaperoning, thereby acting as a negative regulator of histone H3-H4 deposition during chr15 assembly 1. CDAN1 also interacts with CDIN1 and participates in a protein complex whose nuclear import is mediated by importin 4 (IPO4) 2. Functionally, CDAN1 is critical for primitive erythropoiesis, with genetic and animal models demonstrating its essential role in normal red blood cell development 3. CDA1 mutations result in ineffective erythropoiesis characterized by morphologically abnormal erythroblasts in bone marrow 4. The disease represents a key model for understanding erythroid differentiation-proliferation pathways and chr15 organization mechanisms in hematopoiesis 5. Next-generation sequencing has enabled molecular diagnosis and improved understanding of CDAN1-related pathogenesis 4.