From the Guidelines
Surfactant Metabolism Dysfunction Pulmonary 3 (SMDP3), also known as Surfactant Protein C (SP-C) deficiency, is a rare genetic lung disorder caused by mutations in the SFTPC gene, which affects the production and function of pulmonary surfactant. This condition is characterized by severe respiratory distress, typically presenting in infants with symptoms such as rapid breathing, chest retractions, and bluish skin coloration due to low oxygen levels 1. The surfactant is a critical mixture of lipids and proteins that reduces surface tension in the lungs, preventing collapse of the air sacs during breathing.
Key Characteristics of SMDP3
- Caused by mutations in the SFTPC gene
- Affects the production and function of pulmonary surfactant
- Presents with severe respiratory distress in infants
- Symptoms include rapid breathing, chest retractions, and bluish skin coloration due to low oxygen levels
- Inherited in an autosomal recessive pattern, meaning both parents must carry a copy of the mutated gene for a child to be affected
Treatment and Prognosis
Treatment for SMDP3 primarily involves supportive care with supplemental oxygen, mechanical ventilation, and sometimes extracorporeal membrane oxygenation (ECMO) for severe cases 1. Corticosteroids may be used to reduce inflammation, while some patients might benefit from surfactant replacement therapy, though its effectiveness varies. Antibiotics are prescribed if secondary infections develop. The disorder has a poor prognosis, with many affected infants not surviving beyond early childhood, though milder cases may have better outcomes. Lung transplantation might be considered for eligible patients with severe disease.
Genetic Testing and Counseling
Genetic testing is recommended for infants with severe refractory diffuse lung disease (DLD), as mutations in SFTPC, SFTPB, or ABCA3 genes are estimated to occur in approximately 25% of these cases 1. Identifying such mutations can help avoid the risks and burdens of surgical lung biopsy, facilitate decision-making regarding lung transplantation and/or palliative care, and provide counseling for subsequent pregnancies.
From the Research
Definition of Surfactant Metabolism Dysfunction Pulmonary 3 (SMDP3)
- Surfactant Metabolism Dysfunction Pulmonary 3 (SMDP3), also known as Surfactant Protein C (SP-C) deficiency, is a rare genetic disorder that affects the metabolism of surfactant in the lungs 2, 3, 4, 5.
Characteristics of SMDP3
- SMDP3 is characterized by the accumulation of protein related to surfactant dysfunction, leading to cough, hypoxemia, and radiological diffuse infiltration 2, 3.
- It is caused by mutations in the genes encoding surfactant proteins, such as surfactant protein C (SP-C) 2, 4, 5.
Clinical Presentation
- The clinical presentation of SMDP3 can vary, ranging from acute, severe respiratory dysfunction in the neonatal period to chronic respiratory insufficiency in later infancy and childhood 5.
- Diagnosis is established through sequencing of the relevant genes, and lung biopsy with electron microscopy can be a useful adjunct 5.