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Mowat-Wilson syndrome (MWS) is a multiple congenital anomaly syndrome characterized by a distinct facial phenotype, intellectual disability, epilepsy, Hirschsprung disease (HSCR; see this term) and variable congenital malformations.
Prevalence is estimated at 1/50,000 to 1/70,000 live births. Over 200 patients have been reported so far. It seems probable that MWS is underdiagnosed, particularly in patients without HSCR.
The typical characteristic facies of MWS includes a high forehead, frontal bossing, large eyebrows that are medially flaring and sparse in the middle part, hypertelorism, deep set but large eyes, large and uplifted ear lobes with a central depression, saddle nose with prominent rounded nasal tip, prominent columella, open mouth with M-shaped upper lip, and a prominent but narrow and triangular pointed chin. The facies becomes more pronounced with age. Associated HSCR causes constipation which frequently persists after surgery. Patients usually have moderate to severe intellectual disability.Speech is absent or limited to a few words, with onset at around 5-6 years. Seizures are common; all types of seizures (absence, generalized tonic-clonic seizures, myoclonic, and focal seizures) have been reported. Most subjects have a happy demeanor with frequent smiling and a sociable personality. Other associated congenital anomalies include cerebral (agenesis of the corpus callosum), cardiac (patent ductus arteriosus,ventricular septal defect, valvular pulmonary stenosis; see these terms), pulmonary (artery sling, with or without tracheal stenosis), genitourinary (hypospadias, cryptorchidism, vesicoureteric reflux and hydronephrosis), ocular (microphthalmia) and musculoskeletal (pes planus, calcaneovalgus).
MWS is caused by heterozygous mutations or deletions in the zinc finger E-box-binding homeobox 2 gene, ZEB2, (2q22.3) previously called ZFHX1B (SIP1). To date, over 100 deletions/mutations have been reported in patients with a typical phenotype; they are frequently whole gene deletions or truncating mutations, suggesting that haploinsufficiency is the main pathological mechanism. Studies of genotype-phenotype analysis show that facial gestalt and delayed psychomotor development are constant clinical features, while the frequent and severe congenital malformations are variable. In a small number of patients, unusual mutations can lead to an atypical phenotype.
Distinct facies is particularly important for the initial clinical diagnosis and provides the hallmark warranting ZEB2 mutational analysis in all cases, even in the absence of HSCR. Congenital malformations and seizures require early clinical investigation with intervention of several specialists (including neonatologists and pediatricians).
Differential diagnoses include Pitt-Hopkins, Goldberg-Shprintzen megacolon, Smith-Lemli-Opitz and Angelman syndromes (see these terms).
Prenatal diagnosis is available for subsequent pregnancies of parents with an affected child.
The majority of MWS cases reported so far were sporadic, however, germinal mosaicism has been described and recurrence risk has been calculated at 2% .
Management and treatment
Congenital heart disease and HSCR disease may require early surgery during the first days or months of life. Seizures are common and require standard therapy. Genitourinary anomalies may require surgery in the first few years of life. Psychomotor development is delayed in all patients, therefore rehabilitation (physical therapy, psychomotor and speech therapy) should be started as soon as possible. Musculoskeletal anomalies may require orthopedic intervention.
Mortality and morbidity depend on the presence and severity of congenital anomalies. Patients have been reported to live into early adulthood but require assistance with the activities of daily living.