Schematic relationship between ribosome synthesis and SDS, DBA, TCS, CHH, AD, and DC. TCS is depicted by dotted lines, as it does not cause bone marrow failure. Putative functions in ribosomal biogenesis attributed to each gene product include 40S ribosomal subunit maturation, RNA polymerase I (pol I) transcription, rRNA methylation, rRNA cleavage, and pseudouridylation (pseudo-U) of rRNA. Illustration by Frank Forney.