576G>C ATRX mutation in a patient with ATMDS. (A) DHPLC tracing of the exon 8 amplicon from patient no. 4. The lighter and darker purple tracings represent unfractionated peripheral blood and bone marrow from a sample obtained when the patient had 50% erythrocytes with HbH inclusions by brilliant cresyl blue (BCB) staining and 25% HbH on electrophoresis. The brick red tracing represents unfractionated marrow from a time point 6 months later when the amount of HbH by electrophoresis had fallen to less than 1% and only rare HbH inclusions were detectable on supravital staining. The dark green tracing is a wild-type control. (B) Big Dye–generated sequence of 2 subclones (top 2 lines) and unfractionated marrow DNA (bottom line) from patient no. 4, exon 8 (coding strand 5′ to 3′, running left to right). The top line is sequence of a subclone with normal DNA (ie, 576G), the middle line is from one of the subclones demonstrating the 576G>C mutation (arrowhead), and the bottom line represents DNA from unfractionated marrow where a contribution from cytidine (blue, with arrow) can be seen as a minor peak under the primary fluorochrome representing guanidine (black).