Clinically Diagnosed Diamond-Blackfan Anemia with Negative Whole Exome Sequencing in an Infant with Crossed Renal Ectopia: A Case Report

Abstract Background Diamond-Blackfan anemia (DBA) is a rare congenital bone marrow failure syndrome presenting with early-onset anemia and reticulocytopenia. Approximately 30–40% of clinically typical cases remain genetically unresolved on exome sequencing, and a diagnosis can still be established on clinical and morphological grounds when the phenotype is characteristic. Case presentation: We report an 80-day-old female infant of non-consanguineous parentage who presented with pallor, poor feeding, and severe transfusion-dependent anemia with reticulocytopenia since birth. Bone marrow examination showed a normocellular marrow with marked erythroid paucity and an elevated myeloid-to-erythroid ratio, with adequate megakaryocytes and no fibrosis or malignancy. Whole exome sequencing targeting RPS19, GATA1, and TSR2 was non-diagnostic, revealing only a heterozygous variant of uncertain significance in KMT2D. Contrast-enhanced CT urography incidentally identified a non-fused crossed ectopic left kidney. Alternative nutritional, infectious, and inherited marrow failure causes were excluded, and a clinical diagnosis of DBA was made. The infant was managed with packed red blood cell transfusion and supportive care. Conclusion This case illustrates that DBA can be diagnosed on clinical and morphological grounds despite a negative exome sequencing result, and describes non-fused crossed renal ectopia as an anomaly not previously reported in association with DBA, broadening the recognized spectrum of congenital anomalies in this disorder.