An unusual case of hypercapnic respiratory failure

Asphyxiating thoracic dystrophy (ATD also known as Jeune syndrome) is a very rare disorder with an incidence in the United States of 1 case per 100,000-130,000 live births. Chronic alveolar hypoventilation leading to concurrent hypoxia is the main cause of morbidity and mortality in these patients due to its complications. A 22-year-old male with past medical history of ATD and severe kyphoscoliosis presented with progressively worsening shortness of breath for several days. Past surgical history was significant for multiple reconstructive sternal surgeries, his first surgery was at the age of two. His chest exam was without wheezing and was notable for symmetrically decreased breath sounds. Arterial blood gas showed PH 7.17, PCO2 155, PO2 95 and O2 saturation of 97% on 2 L nasal cannulae. PA and lateral chest xrays showed a long and severely narrow thoracic cavity. 2D echocardiography showed left ventricular ejection fraction of 55% and evidence of severe pulmonary hypertension. CT chest angiography showed severe dilatation of the pulmonary artery in comparison to ascending aorta and significant right ventricular enlargement. Right heart catheterization confirmed these findings with a mean pulmonary arterial pressure of 61 mmHg. Within several days of hospitalization, patient developed acute worsening of his chronic hypercapnic respiratory failure thought to be due to worsening of pulmonary arterial hypertension with right heart failure. This in return was attributed to underlying ventilatory failure secondary to severe thoracic dystrophy. ATD is an autosomal recessive genetic disorder. Mutations in the IFT80 gene, which encode for an intraflagellar protein, cause this protein to be defective. Clinically, ATD is characterized by a small, narrow chest and variable limb shortness. While ATD is compatible with life, respiratory failure and infections are often fatal during infancy. Patients that survive past the age of 2 have seen respiratory complications resolve due to less pronounced thoracic malformations, but in our case the main cause of worsening pulmonary function was the degree of pulmonary arterial hypertension and right heart failure. Patients with ATD usually develop progressive hypercapnic respiratory failure due to an abnormally small thorax. Surgical options include lateral thoracic expansion or sternal and chest wall reconstruction. However, these surgeries only add a few years to survival without a definitive cure.