Diamond-Blackfan anemia (DBA) is an inherited red blood cell aplasia that usually presents in the first year of life. The main features are normochromic macrocyt...
Diamond-Blackfan anemia (DBA) is an inherited red blood cell aplasia that usually presents in the first year of life. The main features are normochromic macrocytic anemia, reticulocytopenia, and nearly absent erythroid progenitors in the bone marrow. Patients show growth retardation, and approximately 30 to 50% have craniofacial, upper limb, heart, and urinary system congenital malformations. The majority of patients have increased mean corpuscular volume, elevated erythrocyte adenosine deaminase activity, and persistence of hemoglobin F. However, some DBA patients do not exhibit these findings, and even in the same family, symptoms can vary between affected family members (summary by Landowski et al., 2013).
For a discussion of genetic heterogeneity of Diamond-Blackfan anemia, see DBA1 (105650).
▼ Clinical Features
Gazda et al. (2008) reviewed medical records of DBA7 patients and found that associated physical malformations, predominantly involving the thumb, were seen in 12 of the 18 patients and included triphalangeal thumbs, small extra thumbs, and flat thenar muscles, as well as ventricular septal defect, tetralogy of Fallot, horseshoe kidney, and vesicoureteral reflux. One patient had uterine cancer.
Gerrard et al. (2013) reported 3 unrelated patients with DBA7. A 7-year-old Caucasian boy was diagnosed at birth and had elevated erythrocyte adenosine deaminase (ADA; 608958). He also had patent ductus arteriosus, hypoplastic thumbs, recurrent chest infections, and vitamin D deficiency. The disorder was steroid-responsive. A 5-year-old Indian girl was diagnosed at age 3 months. She had growth retardation and recurrent infections, and was transfusion-dependent. A 7-year-old Caucasian girl was born by cesarean section due to fetal distress, and was diagnosed with anemia at age 12 months. She had growth retardation, recurrent otitis, mouth ulcers, neutropenia, hypoplastic thumbs, scoliosis, Cathie facies, and Sprengel shoulder deformity. Erythrocyte ADA was elevated.
▼ Molecular Genetics
Gazda et al. (2008) screened 196 probands with Diamond-Blackfan anemia for mutations in 25 genes encoding ribosomal proteins and identified 11 different heterozygous mutations in the RPL11 gene in 13 probands and 5 additional family members (see, e.g., 604175.0001-604175.0004). The mutations segregated with disease in multiplex families and were not found in at least 150 controls; functional studies demonstrated defects in the maturation of ribosomal RNAs associated with mutation in the RPL11 gene.
Gerrard et al. (2013) identified heterozygous truncating mutations in the RPL11 gene (see, e.g., 604175.0005-604175.0006) in 3 of 19 patients with DBA who were screened for mutations in 80 ribosomal protein genes.