PRS involves physical changes during development that lead to altered oral cavity anatomy. Since air and food both pass through the mouth and down the throat, breathing and feeding problems are common.
In PRS, the lower jaw (mandible) characteristically has an altered shape and position. Typically, it has a reduced length and is located toward the back (microretrognathia). In turn, these changes in the mandible can influence the tongue’s positioning toward the back of the mouth (a ‘retruded’ tongue). Anatomic anomalies of PRS also frequently include a U-shaped cleft palate, which affects the dynamics of breathing and speech development.
Specifically, the displacement of the tongue toward the back (posterior) of the mouth predisposes it to fall toward the throat. This may obstruct the airway and cause difficulty breathing. This can vary in severity, ranging from mild disturbance to life-threatening respiratory distress. Airway obstruction can also occur during the night, in the case of a related condition called ‘obstructive sleep apnea’. This is a sleep disorder characterized by breathing that temporarily stops and restarts because of periodic blockage of the airways.
Since food traveling toward the gastrointestinal tract also passes through the mouth and throat, feeding difficulties can also arise due to abnormal oral cavity anatomy. Depending on the severity, this can lead to issues like choking (aspiration) or gaining less weight gain than expected (which doctors refer to as ‘failure to thrive’). There is also a higher prevalence of acid (gastroesophageal) reflux in children with PRS.
Other possible manifestations of PRS include cardiovascular and lung conditions, such as heart murmurs, high blood pressure in the arteries of the lungs (pulmonary hypertension), and narrowing of the opening between the lung artery and the right ventricle of the heart (pulmonary stenosis). Anomalies of the musculoskeletal system, including those in the arms, legs, feet, and vertebral column, are also common. Inflammation of the middle ear (otitis media) usually accompanied by repeat ear infections occurs in about 80% of patients, and eye (ocular) defects are noted in about 10% to 30% of patients. Teeth present at birth (natal teeth) are another frequent finding.