In SDS patients, mutation of SBDS stalls 60S maturation and impairs ribosome assembly, resulting in a reduced number of 80S ribosomes.157 Recently, the identification of mutations in another 60S ribosome assembly factors DnaJ Heat Protein Family Member C21 (DNAJC21) and EFL1 support that impaired 60S ribosome maturation as a consequence of defective EIF6 eviction is the primary cause of SDS pathogenesis.158,159. The gene discussed is DNAJC21; the disease is Shwachman-Diamond syndrome.