Aplastic anemia, pediatric aspects

Inherited bone marrow failure syndromes (BMFs) comprise at least one-fourth of children with aplastic anemia, and perhaps up to 10% of adults. The most common syndrome is Fanconi's anemia (FA), with more than 1,000 reported cases. FA is autosomal recessive, with birth defects in ∼75% of patients. It is a DNA repair syndrome, diagnosed by finding chromosomal aberrations in cells treated with clastogenic agents. The major problems in FA are, in order, aplastic anemia, leukemia, and other cancers. There are at least five complementation groups; the gene for Group C has been cloned. Carrier identification and gene therapy are beginning in families at risk for FAC mutations. Dyskeratosis congenita (DC) is primarily X-linked (at Xq28), with autosomal recessive and dominant cases as well. Patients classically have reticulated hyperpigmented skin, dystrophic nails, and mucous membrane leukoplakia. ∼50% develop aplastic anemia, sometimes prior to the DC phenotype, and ∼10% develop cancer. Shwachman-Diamond syndrome consists of exocrine pancreatic insufficiency with neutropenia; ∼25% develop aplastic anemia and 5%-10% develop leukemia. Amegakaryocytic thrombocytopenia presents in infancy, and often evolves into aplastic anemia and/or leukemia. Single cytopenias include Diamond-Blackfan anemia (DBA), which is inherited pure red cell aplasia; transient erythroblastopenia of childhood; Kostmann's syndrome (KS) or infantile genetic agranulocytosis, and thrombocytopenia with absent radii in which there is neonatal thrombocytopenia and absent radii. DBA and KS, particularly the latter treated with G-CSF, may develop leukemia, and solid tumors have been reported in DBA. Treatment for the various BMFs includes bone marrow-transplantation, androgens, and hematopoietic cytokines such as G-CSF. These inherited syndromes thus include various combinations of marrow failure and premalignancy.