Index of Suspicion

Case 1 Presentation

A 10-month-old girl is referred to a tertiary care hospital because of growth failure and tachypnea over the preceding 7 months. She is formula-fed, and her weight gain and development are appropriate for a 3-month-old. Her perinatal history was normal, her birth measurements were at the 50th percentile, and no dysmorphism was noted. Both parents are healthy and are not related biologically; the family history is noncontributory. The patient lives in a remote and medically underserviced community.

Since age 3 months, her weight gain velocity has slowed considerably, despite a normal diet and no problems with swallowing, reflux, or stooling. “Comfortable” resting tachypnea (75 breaths/min) was recorded initially at her 3-month assessment. Marked diaphoresis has been noted occasionally during feedings or sleep. No other abnormalities are documented.

Multiple investigations at a regional general hospital at 6 months of age included a radiograph of the chest that showed right middle lobe opacity. Her ECG was interpreted as normal. Echocardiography suggested no anatomic abnormality of the heart. CT scan of the chest was reported to show left upper lobe hyperlucency presumed to be due to emphysematous changes. Central pulmonary arteries of “generous” size were described. CBC, venous blood gases, and sweat test yielded normal results. Fortified formula was given.

On physical examination today, the infant's weight is below the 3rd percentile. She exhibits tachypnea, moderate distress, and subcostal retractions. Her heart rate is 120 beats/min, blood pressure is 90/50 mm Hg, and peripheral oxygen saturation is 98%. With crying, there is no visible cyanosis, but the oxygen saturation declines transiently to 90%. Her chest appears mildly hyperinflated and the precordium mildly hyperdynamic. There is a palpable left parasternal impulse, but no thrill. Her lung fields are clear with prominent breath sounds; no heart murmur is noted. The second heart sound is split …