Surfactant protein C deficiency in a full term infant
The present case has been reported in the Journal of Pediatrics. A 2-month-old, full-term, immunized female infant with chronic congestion presented with difficulty feeding, poor weight gain, and hypoxia. One month prior to presentation, she began taking smaller volumes of formula, became fussier with feeds, and developed tachypnea unrelated to feeds.

She was breastfed with formula supplementation but had suboptimal weight gain. On day of admission, she was found to have oxygen saturations in the 80s at her pediatrician's office. In the emergency department, she had central cyanosis, tachypnea, and increased work of breathing. Her lungs were clear to auscultation. Her hypoxia improved with supplemental oxygen.

Venous blood gas, electrolytes, and complete blood count were normal. Chest radiograph demonstrated diffuse parenchymal haziness. Respiratory viral panel was negative. She was admitted for a presumed infectious respiratory process. Further questioning revealed a family history of “chronic pneumonitis of infancy” because of unknown etiology in paternal grandmother and second cousin.

During admission, she was unable to wean to room air despite minimal nasal secretions. She initially had adequate feeding and weight gain with fortified formula but developed diaphoresis and tiring with feeds. Based on the paternal family history, genetic testing for interstitial lung diseases was obtained. The patient was found to be heterozygous for surfactant protein C deficiency, and she was eventually discharged on supplemental oxygen. Follow-up computed tomography scan with contrast showed patchy ground-glass opacities in the right upper and middle lobe, and bilateral lower lobes.

Major takeaways:-
- Surfactant deficiency is often considered in the differential of premature neonates presenting with respiratory distress syndrome.

- It should also be considered in infants beyond the neonatal period with tachypnea, cough, hypoxia, and failure to thrive.

- Genetic diseases with autosomal dominant inheritance may have variable penetrance, and a negative parental medical history does not definitively rule out the diagnosis.

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