CSTB and Global developmental delay: For instance, Mancini et al (2016) reported one of the patients with a homozygous for nonsense mutation in CSTB. The patients, homozygous for a c.202C>T mutation leading to a truncated form of the CSTB protein, named R68X, have severe developmental delay, dyskinesia and microcephaly starting at 3 months of age (Mancini et al, 2016).