Hypoventilation Syndrome Secondary to Club-Shaped Chest Wall Deformity.

Hypoventilation syndrome is defined as a decrease in alveolar ventilation leading to hypercapnia (PaCO2 > 35-45 mmHg) and hypoxemia. There are multiple causes of hypoventilation syndrome described in the literature, of which central and obesity-related causes are more prevalent. Other causes such as neuromuscular disorders and chest wall deformities are relatively less common. Multiple defects in the normal functioning of the respiratory function are implicated in the pathophysiological mechanism of hypoventilation syndrome, such as a hypoactive central ventilatory drive, decreased airway function, ventilation-perfusion mismatch, defective pulmonary mechanics, and respiratory muscle fatigue. Patients often present with dyspnea, headache, lethargy, repeated pulmonary infections, hypoxia that usually improves with low flow oxygen, and hypercapnia that may alter mental function. Nocturnal or diurnal assisted mechanical ventilation is proven to be an effective therapy for patients suffering hypoventilation syndromes. We describe a case of a 47-year-old woman with hypoventilation syndrome resulting from a rare chest wall deformity with inward protrusion of the costochondral junction of the ribs with ossification of the costal cartilage on CT who presented with dyspnea and hypercapnia.