Despite their relatively similar size, very few mutations were found in B-type lamins compared to lamins A and C. There were 13 mutations associated with LMNB1, all causing neural tube defects (NTDs) including microcephaly (n = 5), spina bifida (n = 7) and anencephaly (n = 1). The gene discussed is LMNB1; the disease is anencephaly.