ASXL1 and Bohring-Opitz syndrome: Bohring-Opitz syndrome (BOS) was first described by Bohring et al in 1999.[1–4] The patients they described had several features in common, including a prominent metopic suture, hypertelorism, exophthalmos, cleft lip and palate, limb anomalies, difficulty feeding, and severe developmental delays.[5] In almost 50% of cases that meet the clinical criteria for BOS, de novo frameshift and nonsense mutations in the additional sex combs-like 1 (ASXL1) gene have been detected,[2,6–14] suggesting that loss of function of this gene is the major cause.