Bohring-Opitz Syndrome / ASXL1

Definition Bohring-Opitz Syndrome (BOS)

Bohring-Opitz Syndrome (BOS) is a ultra rare congenital genetic condition characterized by intrauterine growth restriction (IUGR) and failure to thrive with feedings difficulties and severe developmental delay. Distinctive facial features and typical BOS-posture are described in different expression and may include micro and/or trigonocephaly, naevus flammeus, prominent eyes, puffy cheeks as well as flexion at the elbows and wrist and
reduced muscle tension of the body (trunk) with hypertonia (increased tension of the muscles) of the extremities . ( → read more about clinical features and symptoms of Bohring-Opitz Syndrome).

In 2018, there are less than 60 children clinical and molecular diagnosed with this syndrome and presented in medical articles worldwide (Russell, B. et al. 2018). To date (2021) there are about 200 participants registered in the BOS/ASXL Patient registry. (U.S. National Libary of Medicine, ClinicalTrials)


Bohring et al. (1999) presented four patients who had similar features to two cases that had already been reported by Oberklaid et al. (1975) and Addor et al. (1995). Bohring suggested that these six children either represented the severe end of the clinical spectrum of ‘Opitz trigonocephaly C syndrome’ or comprised a separate entity. Since then there have been further reports of individual patients with similar findings. The terms ‘Bohring’, ‘Bohring-Opitz’ and ‘C-like syndrome’ have all been used to describe this condition (Greenhalgh et al. 2003). Because Oberklaid et al. (1975) reported another case there is also the name ‘Oberklaid-Danks-Syndrome’ for ‘Bohring-Opitz-Syndrome’ (Hasting et al. 2011).