Mowat-Wilson syndrome (MWS) is a relatively newly described multiple congenital 
anomaly/mental retardation syndrome. Haploinsufficiency of a gene termed ZFHX1B 
(also known as SIP1) on chromosome 2 is responsible for this condition, and 
clinical genetic testing for MWS recently became available. The majority of 
reports in the literature originate from Northern Europe and Australia. Here we 
report our clinical experience with 12 patients diagnosed with MWS within a 
2-year period of time in the United States, with particular emphasis on clinical 
characteristics and management strategies. Individuals with this condition have 
characteristic facial features, including microcephaly, hypertelorism, medially 
flared and broad eyebrows, prominent columella, pointed chin, and uplifted 
earlobes, which typically prompt the clinician to consider the diagnosis. 
Medical issues in our cohort of patients included seizures (75%) with no 
predeliction for any particular seizure type; agenesis of the corpus callosum 
(60% of our patients studied); congenital heart defects (75%), particularly 
involving the pulmonary arteries and/or valves; hypospadias (55% of males); 
severely impaired or absent speech (100% of individuals over 1 year of age) with 
relatively spared receptive language; and Hirschsprung disease (50%) or chronic 
constipation (25%). The incidence of MWS is unknown, but based on the number of 
patients identified in a short period of time within the US, it is likely 
greatly under recognized. MWS should be considered in any individual with 
severely impaired or absent speech, especially in the presence of seizures and 
anomalies involving the pulmonary arteries (particularly pulmonary artery sling) 
or pulmonary valves.