Discussion:
We present the complex case of a patient with VACTERL association, SMA, and pulmonary stenosis. Evaluation of the tracheobronchial system should be considered for all children with VACTERL association who present with respiratory symptoms. Longer-term complications of TEF can include tracheomalacia, TEF recurrence, esophageal stricture, and gastroesophageal reflux disease.9,10 Congenital tracheal stenosis5 and bronchial stenosis6 have been reported in two infants with VACTERL association. There should be a low threshold for investigation when patients with VACTERL association present with persistent or severe respiratory symptoms.10 Our patient differed from the prior cases as he did not require overnight ventilatory support until 2 years of age and did not show overnight desaturation until 7-1/2 years of age. His clinical presentation was further complicated by his diagnosis of SMA.
Concomitant neuromuscular diseases can present a challenge when evaluating respiratory dysfunction. Patients with progressive neuromuscular disorders demonstrate decline in respiratory status with time. Ineffective cough, weak accessory muscles leading to nocturnal hypoventilation, and sleep-disordered breathing are common.11 Due to imbalance between respiratory muscle strength and increased respiratory load from scoliosis and chest wall deformities, patients with neuromuscular disorders are at risk for respiratory failure.12 Specific diseases can show a predilection for specific respiratory muscles. Infants and children with an untreated, severe form of SMA show prominent intercostal muscle weakness with accompanying paradoxical abdominal breathing.13 In SMA, diaphragm function appears to be relatively spared.14 Neuromuscular diseases such as Duchenne muscular dystrophy show preferential weakness of expiratory muscles and diaphragm involvement while collagen 6A-related congenital muscular dystrophies may show a restrictive pattern of respiratory weakness resulting from more severe diaphragm weakness.8 Sitting versus supine forced vital capacity (FVC) testing can be particularly helpful in this regard.15
Patients with neuromuscular disease are anticipated to have normal lung parenchyma and airway resistance, at least early in their presentations.11 The high inspiratory pressure requirements in our patient to overcome his stenotic airway would not be expected in neuromuscular respiratory dysfunction. The anatomic lesion observed also explains the ventilator dysynchrony observed in our patient. Ultimately, both airway and ventilation issues need to be considered when complex patients present with respiratory dysfunction. In patients with underlying genetic syndromes and neuromuscular conditions, the described specific clinical patterns of respiratory dysfunction combined with polysomnogram data and imaging findings can help clarify the etiology of respiratory dysfunction, and guide management options.