Surfactant Protein B Deficency

Abstract

Surfactant Protein B is critically responsible for the functioning of healthy lungs. In the absence of Surfactant Protein B adverse lung condition such as acute respiratory distress syndrome arise in infants victims. Due to this, SP-B's condition has drawn the attention of medical researches. Physiological ailments such as lung failure, molecular defects and cellular deficiencies in infants are associated with opportunistic to Surfactant Protein B syndrome. This relation and linkage stirs up the development of various treatment strategies of neonatal respiratory diseases. Surfactant Protein B syndrome was first identified as the main cause of congenital alveolar proteinosis, a condition where two infants from the same mother exhibit distinct histopathologic physical appearance, since their alveoli contain lipid rich acid Schiff-positive and granular proteinaceous material. Infants suffering from Surfactant Protein B syndrome exhibit foamy alveolar macrophages and desquamated alveolar epithelial cells. Acquired Sporadic and congenital alveolar proteinosis are the main clinical forms of alveolar proteinosis associated with infants. Since SP- B syndrome has become rampant and established in infants with respiratory distress, this paper evaluates the causative agents and implications of SP-B giving various recommendations for the use of Surfactant therapy in diverse clinical situations. This includes subjecting newborns to prophylactic natural surfactant therapy immediately after incubation. By so doing, paper primarily relates Surfactant Protein B syndrome to the clinical setting while exploring the implications for the neonatal nurse practitioner.

Definition of the Disease, Incidence

SP- B Deficiency is an inherited illness by newborn babies leading to severe respiratory failure in the early stages of life and is resistant to surfactant therapy, mechanical ventilation and extracorporeal membrane oxygenation. Genetic examination of infants suffering from Surfactant Protein B Deficiency shows identical mutation in surfactant protein gene gotten in many unrelated kindred. This interrupts the functioning and composition of pulmonary surfactant. Reported incidence of approximately 0.8 infants out of 1000 obtained from Missouri Department of Health Newborn Screening Program indicates that Surfactant Protein B syndrome is a major factor in causing pathophysiology of respiratory distress syndrome (Refere and Wilmott, 2012). The inability of young infants to produce surfactant and the structural immaturity of their lungs increases with the increase in gestation period. This indicates that out of 1000 babies, about 25% of them are caught with SP-B syndrome at 34th week adding up to 80% babies affected in a period of less than 54th week (Kendig and Wilmott, 2012). The 121ins2 mutation never showed in South African or Korean cohorts instead, there was similar correlation and frequency in Norwegian and Missouri cohorts. This indicated 173 incidences of infants suffering from Surfactant Protein B syndrome out of every 4000 samples of infants from Missouri cohort that were screened (Refere and Wilmott, 2012).

In the incidence describing two siblings with the condition of histopathologic due to congenital alveolar proteinases, examined lung tissues reveals the absence in one of the making blocks of surfactant protein called SP-B protein . This suggests that the incident of Surfactant Protein B syndrome causes respiratory failure in children possessing congenital alveolar proteinosis, which is an inherited deficiency version of SP-B through pretranslational process.

The two siblings had a condition called congenital pulmonary alveolar proteinosis and in particular, deficiency of Surfactant Protein B. These SP-B disease incidences support the hypothesis attributing inherited SB-P syndrome as being the cause of respiratory diseases in babies bellow the age of one year. Some evidence portrays a combination of synthetic SP-B peptide and surfactant phospholipids displaying physical characteristic similar to the ones exhibited by native surfactant (Refere and Wilmott, 2012).

Disease Etiology and Pathogenesis

Surfactant Protein B syndrome is caused by inherited mutation in the form of surfactant protein B gene on chromosome 2.This leads to complete or in some cases partial absence of Surfactant Protein B, a condition referred to as autosomal recessive condition. Children exhibiting respiratory distress immediately after birth despite assisted ventilation need to be screened for Surfactant Protein B syndrome. Also diagnosis of both the child and parent for genetic mutation possibilities is necessary. SP-B deficiency is associated to poor prognosis and therefore infants with this disorder barely survive beyond the first few months after birth unless they are subjected to processes of lung transplantation (Popper, 2017).

The occurrence of surfactant dysfunction due to inherited mutation causes deaths to over 1 million infants'world over (Gleason, Devaskar and Avery, 2012). Surfactant Protein B syndrome have different inheritance patterns that depend on diverse genetic cause. SP-B is caused by mutation process in SFTPG gene, which is an instruction responsible for making Surfactant Protein B from a distinct gene. This causes abnormality in the composition of phospholipids and proteins responsible for normal breathing. Without normal surfactant B protein, the various tissues and cells surrounding the air sacs of the lungs bond together during the periods of exhalation due to surface tension. This eventually causes the alveoli to collapse and eventually causes Surfactant Protein B syndrome. The presence of surfactant in the system of infants, aids in lowering surface tension responsible for easy breathing and avoiding lung collapse. Corrupted composition of Surfactant Protein B causes the surface tension that lowers properties of surfactant around the lung tissue. In addition, Surfactant Protein B syndrome is caused in circumstances where SP-B fails to form lamella bodies, which are responsible for packing the phospholipids and proteins making up surfactant around the lungs cells of the infants. This prevents the vital processes that surfactant protein must undergo to mature up and become functional.

In addition, Surfactant Protein B syndrome is caused through malfunctioning of ABCA3 genes, which are responsible for the production of proteins, involved in the synthesis of surfactant. Without production od surfactant in the infants, the tissues that surrounds the air sacs of the lung will clump together after exhalation due to surface tension force, resulting in difficulty during breathing and collapse of alveoli as a result of Surfactant Protein B syndrome (Cremona et al, 2010). This causes infants to develop difficulties in filling the lungs with air and eventually impairs the delivery of oxygen to the body. The ABCA3 is also responsible for packing and transporting phospholipids and proteins around alveoli where through molecular interaction Surfactant Protein B is formed. An impaired ABCA3 protein retards the formation of lamellar bodies which are responsible for the processing of surfactant B protein hence causing the condition of Surfactant Protein B syndrome. This will cause infants to have respiratory difficulties since there is premature formation of Surfactant Protein responsible for effective functioning of the lungs.

Pulmonary surfactant is composed of lipids and protein compounds which in the long run reduce the surface tension between the regions holding air and liquids in the lungs of infants. Deficiency of pulmonary surfactant is the fundamental cause of respiratory disorder in babies bellow one year old. Various specific proteins identified to be associated with surfactant function include glycoprotein responsible for surfactant metabolism and host defense (SP-C) and hydrophobic proteins which contain low molecular mass to facilitate the adsorption rate of surfactant phospholipids into air-liquid interphase (Broaddus et al 2015). Surfactant Protein B is responsible for positive metabolism and functioning of body systems .However, inherited Surfactant Protein B syndrome in infants causes respiratory diseases.

Phenotype and Natural History

The phenotypic unpredictability of Surfactant Protein B syndrome is attributed to inherited surfactant protein deficiency which is an often cause of respiratory failure in children bellow the age of one year. This is due to phenotypic mutation of frameshift phenotype in families with either two or three of total siblings exhibiting Surfactant Protein B syndrome. Infants with abundant SP-B suggest phenotypic heterogeneity in CAP (Cottin, Cordier and Richeldi, 2015). Lung ultrastructural defects including reduced number of lamellar bodies, low secretion of surfactant lipids and absent tubular myelin indicates phenotypic derangement of surfactant metabolism. The natural history of Surfactant Protein B syndrome is dated back form the year 1993 in a full-term infant of bellow one year old. With rare exceptions, SP-B deficiency is considered as the fatal diseases having only one therapeutic option of lung transplantation. Infants with ABCA3 gene syndrome exhibits severe lung ailment due to SP-B deficiency. This condition may become progressively worsening with time and may results in neonatal lung disease. The overall slim survival chances of infants with Surfactant Protein B syndrome, results from ascertainment bias instead of reflecting all the natural history spectrum of the disease.

No formal research has yet evaluated the genotype-phenotype correlation of Surfactant Protein B syndrome but complete mutation on the overall alleles has been associated with remote onset and severity of the disease. Whereas interaction with older patients undergoing milder experience of Surfactant Protein B syndrome usually have one missense mutation that have the possibility of retaining some functional activities of surfactant protein. The natural history on lung ailment due to Surfactant Protein B syndrome is highly associated to genetic mutation as reported in the newborn. Adults with Surfactant deficiency may show asymptomatic condition for a long time before their lungs are altered due to such hereditary gene mutation. This makes the SP-B condition variable and difficulties in interpretation of potential drug therapy. There is lack of specific therapy related to Surfactant Protein B syndrome instead doctors have always insisted on pulse dose steroids as a glucocorticoids goes up. Also, there has been the use of Hydroxychloroquine and azithromycin, but their efficacy is limited to anecdotal findings. Lung transplant has been conducted on infants with end-stage lung diseases because of Surfactant Protein deficiency and mutations (Cottin, Cordier and Richeldi, 2015).

Management

In managing Surfactant Protein B syndrome in infants, several tests have been done to help in diagnosis process. This include conducting laboratory testing to rule out the possibility of occurrence of diseases with same symptoms with Surfactant Protein B syndrome, such test may include cystic fibrosis or immunodeficiency (Polin, Fox and Abman, 2011). To clearly determine the various mutations in the genes of then child, a high resolution computerized technology is required for scanning of the lungs such as bronchoscopy conducted to verify for infections, signs of aspirations into the respiratory surfaces and eventually inflammation. However, in older children, pulmonary functioning testing is in many occasions performed in outpatient environment and often indicate decreased lung functioning. In addition, lung biopsy may be conducted to ascertain useful information with the possibilities of ruling out other respiratory diseases with exact clinical presentation.

The management and prognosis of Surfactant Protein B syndrome is variable depending on the seriousness of the infant condition. Some situations call for lung transplantation while others do not. In all circumstances of Surfactant Protein B syndrome, optimizing nutrition for effective growth and prevention of respiratory infections are of importance to the overall health. In addition, managing Surfactant Protein B syndromes require assisted breathing through ventilator. Currently there is no specific clinical treatment of Surfactant Protein B syndrome hence for the victim infants, surfactant replacement therapy serves to improve the respiratory status transiently even though it is not the most appropriate in treating Surfactant Protein B syndrome. Consideration of lung transplantation in viable, however, with critically ill and unstable infant, the pre-transplant period is attributed to possess high chances of the child dying. A 5 years old infant has about 50 survival chances in cases of lung transplantation. In older children with slighter version of Surfactant Protein B syndrome, corticosteroids and hydroxychloroquine are considered as appropriate methods to manage SP-B deficiency (Shanley, Wheeler and Wong, 2007).

Recurrence Risk and Genetic Counseling

Surfactant Protein B syndrome recurrence risk is evident amidst people who trace their ancestry to a precise geographical location. Individuals in an ethnic cluster possess high probability of sharing certain versions of their genes. In genetic counseling, keeping family medical history is vital. These records can hint on medical conditions that may frequent the family. Mastering the arrays of Surfactant Protein B syndrome in the family history puts health care professionals in the right position to diagnose whether individual or related family members of the coming future generation may be at risk of developing Surfactant Protein B syndrome. Family medical history pertaining Surfactant Protein B syndrome discloses people or families with high prevalence of having SP-B syndrome such as respiratory diseases, lung failure and breathing difficulties. These complex disorders are results of influence of combination of specific genetic factors, environmental condition and the choice of lifestyle.

Surfactant Protein B syndrome history among families can also avail information about the probable risk of rare versions of the diseases caused by mutation in single gene. Knowing one's family medical history regarding Surfactant Protein B syndrome, will enable an individual to take steps in reducing the risks of contracting such conditions. This can be achieved through frequent screening of new born children, adopting healthier lifestyle and subjecting newborns to ventilated surrounding. Victim parents as well can learn to get into regular exercise, quit smoking and check on diet to help in reducing the possibilities of mutations leading to infants inheriting Surfactant Protein B syndrome associate with respiratory and lung complications. Clinical genetic counseling recommends talking to families about their medical conditions as the sure way of obtaining medical information relating to family history. Additionally, retrieving medical records from obituaries and death certificates documents can as well help in complete assessment of family medical history. This information is vital and should be kept up-to-date and to be shared by health care providers in case of need (Polin,Fox and Abman ,2011).

It is fundaments to note that chances of passing on Surfactant Protein B syndrome applies during pregnancy. If a couple has a child with SP-B deficiency, the probability of having successive children suffering from the same syndrome is 25% since having one victim infant does not prevent inheritance of such condition by future children (Pacholok and Stuart ,2011). Clinical counselling admits that even though the chances of genetically inheriting Surfactant Protein B syndrome appears to be straightforward, other factors such as children family history and outcomes of genetic testing at times aggravate those likelihoods. Additionally, some infants suffering from lack of Surfactant Protein B due to genetic mutation hardly develop any health problem otherwise in extreme cases may experience a mild symptom of the illness. I any case a disease that prevails in a family lack a precise inheritance pattern, foreseeing the probability that a child will adopt the condition seems very difficult and only Recurrence risk and genetic counseling can help individuals understand these chances and translate into individuals making informed maternity decisions about the health of their children and their health as well. This has the effect of simplifying estimations on the chances of developing Surfactant Protein B syndrome by infants and passing it on to the next generation through mutation (Popper, 2017).

Implications for Advanced Practice Nursing

Maternal status has implication on the fetus and neonatal as indicated by advanced practice nursing. This is because both the body system of the fetus and the mother coexist together for the whole nine months period (Popper, 2017). The body size of the woman and health status has the capability of causing disorders in the infant. The status of the woman prior to pregnancy also has implications on the future pregnancies such that when previous births are characterized by Surfactant Protein B syndrome therefore the future pregnancies and births is susceptible to surfactant deficiency. Disorders due to lack of surfactant protein in the system of an infant or other similar conditions can possess neonatal or fetal effects. In addition mothers can transfer SP-B disorder as result of abruption and bacterial exposure during pregnancy. This makes it fundamental to understand maternal complications and their effects on infants as imperative part to practicing nurses and other caregivers.

Exogenous surfactant therapy has proved well established in the new born children experiencing respiratory distress. Many aspects of SB-P Implications for advanced practice nursing have been evaluated in systematic reviews and high-quality trials giving variety of clinical situation in handling surfactant deficiency in infants. Advanced care nursing has evaluated substances such as albumin and meconium as among factors inhibiting surfactant functioning. Caregivers have proposed more than 50% oxygen availability for those incubated infants with meconium aspiration syndrome due in insufficient surfactant Protein in their system (Kendig and Wilmott, 2012). Surfactant lavage for both albumin and meconium aspiration syndrome are effective but growing resistance implication requires for further study since there has only been a small controlled trial. This controlled trial showed possible short term physiological benefits and it lacked clinically significant benefits as compared to various groups with restricted rescue surfactant therapy. Also, the application of surfactant replacement therapy in neonatal SP-B syndrome been inadequately studied. A recent analysis of infants of closely related ages, having respiratory failure showed that those infants exhibiting the presence of sepsis and were treated with surfactant had a 40% decrease in the need for extracorporeal membrane oxygenation, showing surfactant therapy to be beneficial. Advanced practice nursing recommends sick newborn infants suffering from SP-B syndrome and other related respiratory distress to be subjected to exogenous therapy (Shanley, Wheeler and Wong, 2007).

Persistent respiratory insufficiency in infants due to Surfactant Protein B syndrome is common in children of less than 30 week gestation. However, the status of S P- B has not been studied and clearly evaluated in this condition. Advanced care rates 75% chronically ventilated premature infants to possess a specifically analyzed surfactant aspect with abnormal role. This observation was attributed to clinically evident respiratory deterioration. This speculates that incidents of infection are among the causes of reduced content of SP-B in surfactant, resulting in surfactant dysfunction and retardation of respiratory condition in infants. This if the most fundamental description by Advanced practices nursing of surfactant dysfunction and the functions of hydrophobic surfactant protein in chronically ventilated premature infants (Cremona et al, 2010).

Conclusion

In conclusion, it is not known whether all children showing conditions of congenital alveolar proteinosis are all deficient of SP-B. However, SP-B is responsible for the development of myelin. The absence of myelin is associated with other genetic deficiencies other than Surfactant Protein B syndrome. This indicates that histopathological appearance of the alveoli proteinosis emanates from diverse conditions other than SP-B deficiency or deficiency of surfactant proteins which are yet to be determined. Besides SP-B deficiency, there are diverse surfactant dysfunctions that are genetically caused. Surfactant administration through endotracheal intubation is the only means proven to be safe in delivering surfactant to the lungs of SP-B deficiency victims. All attempts to administer surfactant through intrapartum hypo-pharyngeal instillation have always proved futile therefore relating Surfactant Protein B syndrome to the clinical setting and exploring the implications for the neonatal nurse practitioner.

Reference

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