Last updated:
1/15/2025
Years published: 2025
NORD gratefully acknowledges Tam Nguyen, MD Candidate, Anna Laemmle, MD Candidate, University of South Florida Morsani College of Medicine and Katiana Garagozlo, MD, Assistant Professor, University of South Florida Morsani College of Medicine, for the preparation of this report.
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Summary
Surfactant protein B deficiency is a rare inherited disorder that can lead to interstitial lung disease. Characteristic features of this condition include increased breathing rate (tachypnea), gray/blue pallor (cyanosis), grunting, nasal flaring and increased oxygen demand1. Infants typically develop these symptoms within a few hours after birth, which usually progresses to fatal respiratory failure within three to six months.2
Surfactant is a mixture of proteins and fat produced by alveolar cells in the lungs that help with breathing.4
Surfactant B protein deficiency is caused by changes (variants) in the SFPTB gene and can be inherited in an autosomal recessive pattern.1
The diagnosis of surfactant protein B protein deficiency is suspected based on signs and symptoms. Definitive diagnosis is confirmed with genetic testing.
This condition is very serious and progresses very quickly. Supportive care can help manage symptoms temporarily, but it cannot address the underlying issue of surfactant deficiency.
A lung transplant is currently the only definitive treatment for surfactant B protein deficiency. 3,4 Without a lung transplant most infants with this condition do not survive beyond the first few months of life due to respiratory failure. However, people who have a lung transplant are also at higher risk of many severe health problems as are infants who receive a lung transplant for other illnesses.5 For infants unable to have lung transplantation, supportive management and monitoring of symptoms remain the mainstay of care.
It is important to note that there are reports of milder cases of lung disease in children with SFPTB variants that cause a partial surfactant protein B deficiency.3,4,6
Immediately after birth, infants may appear well, without symptoms that are concerning for respiratory illness. Shortly after birth, typically within hours, infants may develop signs of respiratory distress including:
Interventions for respiratory failure and surfactant replacement therapy typically only provide temporary relief of symptoms. Symptoms continue to worsen over time.
Surfactant protein B deficiency is caused by changes (variants) in the SFTPB gene. Over 40 different SFTPB gene variants can cause the disease.1,7 These variants prevent the production of functional surfactant protein.
Surfactant proteins help to decrease surface tension, which keeps the alveoli open and prevents the alveolar cells from collapsing during expiration. The role and genetic makeup of various surfactant proteins are well-characterized. Surfactant B protein is one such component that is involved in surfactant’s role of reducing surface tension.4
This condition is inherited in an autosomal recessive pattern. Recessive genetic disorders occur when an individual inherits a disease-causing gene variant from each parent. If an individual receives one normal gene and one disease-causing gene variant, the person will be a carrier for the disease but usually will not show symptoms. The risk for two carrier parents to both pass the gene variant and have an affected child is 25% with each pregnancy. The risk of having a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents is 25%. The risk is the same for males and females.
In the United States, the estimated incidence of surfactant B protein deficiency is 1 in 1 million live births.1
A diagnosis of SP-B Deficiency should be considered in infants with symptoms of respiratory distress or respiratory failure that do not improve after 5 days of life.3 Brief, temporary relief with respiratory interventions may also be an indicator.1,3 Many tests can aid in diagnosis such as:
Definitive diagnosis is obtained through genetic testing which can identify variants in the SFPTB gene. Genetic testing is also available for the parents of the infant. Prenatal testing during future pregnancies is possible from a sample of amniotic fluid or chorionic villi.1
Currently there are no specific treatments available for surfactant protein B deficiency. Surfactant replacement therapy may temporarily improve respiratory status, but this is not a long-term treatment plan. In children with milder forms of the disease, there is some data suggesting the efficacy of corticosteroids and hydroxychloroquine to stabilize the disease process until the patient can receive a lung transplant.
The multidisciplinary team for children with this diagnosis should include neonatologists, pediatric pulmonologists, geneticists, radiologists and pathologists.
Genetic counseling is recommended for families with an affected child.
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For information about clinical trials sponsored by private sources, contact: www.centerwatch.com
For information about clinical trials conducted in Europe, contact: https://www.clinicaltrialsregister.eu/
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