Mutations in the occludin (OCLN) gene cause a recessively inherited severe human disorder of microcephaly and band-like calcifications with polymicrogyria (BLC-PMG) characterized by loss of cortical convolutions, shallow or absent sulci, and multiple small gyri giving the cortex surface a roughened irregular appearance (Abdel-Hamid et al., 2017; O'Driscoll et al., 2010; Jenkinson et al., 2018; Aggarwal et al., 2016; Elsaid et al., 2014). The gene discussed is OCLN; the disease is microcephaly.