Bone marrow failure syndromes.

Laboratory diagnosis of inherited bone marrow failure syndromes includes general evaluations, such as blood counts, examination of the peripheral blood smear for morphology, and bone marrow aspirates and biopsies, which may help the clinician classify the patient, particularly if there are no characteristic physical anomalies. Specific diagnoses require unique tests that are only available for a few of the diagnoses. The most useful is chromosome breakage in the diagnosis of FA, with gene mutation analysis or mapping about to become the gold standard when all of the FA genes have been cloned. The diagnosis of DC remains clinical at this time, although linkage to Xq28 and skewed maternal X inactivation may be helpful in some families. Laboratory proof of SD may be provided by decreased serum trypsinogen or other evidence of exocrine pancreatic insufficiency. CHH is substantiated when absent central pigment in hair is found and when it is mapped to 9p21-p13. The only mitochondrial syndrome, PS, is proved with demonstration of deleted mitochondrial DNA. RD is diagnosed from blood and marrow studies that demonstrate lack of lymphoid as well as myeloid activity. Amega requires absent or abnormal marrow megakaryocytes; if radii are also absent, the diagnosis is TAR. DBA usually has elevated red-cell ADA, and the DBA locus may map to 19q13. KS is diagnosed in patients who have congenital nonimmune severe neutropenia. Clinical suspicion of particular diagnoses can often be substantiated by laboratory tests of varying specificity.