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January - March 2008: 
Volume 21, Issue 1

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Primary spontaneous pneumothorax in childhood
Abstract
SUMMARY. Primary spontaneous pneumothorax (PSP) is defined as pneumothorax occuring in the absence of trauma or underlying lung disease. PSP is rare in childhood and occurs mainly in two age groups, neonates and adolescents. Purpose: Three cases of PSP treated in 2006 are presented, with a literature review. Method: Analysis of patients’ medical records and a short review of the relevant literature. Results: The patients were a 2 day-old female neonate and two adolescent boys aged 12 and 16 years respectively. The adolescent boys both had tall, thin stature with low body mass indices for their age. All the patients were treated with tube thoracostomy, which was removed after a mean of 3.6 days. In one of the adolescents high-resolution CT was normal, although examination of two male relatives revealed subpleural apical blebs and bullae (familial PSP). No recurrences were observed in any of the patients during hospital stay or follow-up for a mean of 1.1 year. Conclusions: PSP is almost always associated with subclinical emphysema-like lesions (blebs and bullae) in the apical regions of the lung. In children, PSP usually occurs in adolescence, affecting mainly tall, thin boys, but it is also seen in neonates, especially premature infants. The disease is usually sporadic, but familial cases account for up to 10%. PSP is usually treated with tube thoracostomy. More invasive methods such as thoracotomy or thoracoscopy with excision of the involved lung parenchyma and pleurodesis aim at preventing or treating PSP recurrences, which are encountered frequently (16-52%). Pneumon 2008; 21(1):52–59
Full text
Introduction

Pneumothorax (PTX) is the collection of air in the pleural cavity, resulting in secondary ipsilateral lung collapse. It is classified as spontaneous, traumatic and iatrogenic PTX. Spontaneous PTX is subdivided into primary and secondary spontaneous PTX. Primary spontaneous PTX (PSP) results from rupture of subpleural emphysematic blebs, bullae or larger cysts in the absence of underlying lung pathology, and is most frequently encounteredin tall, thin adolescent boys or young adults. Secondary spontaneous PTX is caused by underlying lung disease, such as cystic fibrosis, Pneumocysti Carinii pneumonia and, more rarely, asthma, bronchiolitis, autoimmune diseases, congenital cystic adenomatoid malformations and chest trauma1-3.

PSP may occur either sporadically or following a familial pattern, or as a part of a syndrome. Three cases are presented of PSP treated during the year 2006, each with unique clinical characteristics.

Method


The medical files of three patients with PSP treated in the 1st Paediatric Surgical Department of the Aristotle University of Thessaloniki during the year 2006 were studied. Special emphasis was given to the family history, and imaging studies were performed in other family members of the affected children, when a familial pattern of inheritance was suspected.

Case Presentation


The patients were a 2 day-old female neonate and two adolescent boys aged 12 and 16 years (mean age 9.34 years, median age 12 years).

The first case concerned a 2 day-old female neonate with a history of prematurity (36 weeks gestation), transferred from a neonatal unit because of respiratory distress, with low arterial oxygen saturation (92-95%), abnormal blood gas values (paΟ2=80mmHg, pCO2=51mmHg, with FiO2 100%) and pneumothorax detected on a plain chest X-ray. The fetal, obstetric and perinatal history was normal apart from prematurity, and there were no indications of underlying lung pathology. The family history was negative for similar incidents. The posteroanterior chest X-ray showed a large right pneumothorax (Figure 1). A thoracostomy tube was inserted in the 4th intercostal space and connected to a closed drainage system. Arterial oxygen saturation improved instantly, and postoperative X-ray showed that the pleural air had been removed and the lung had reinflated. The chest CT-scan was normal. The thoracostomy tube was removed on the 2nd day after drainage and the patient was discharged after 4 days. During follow-up for 1 year no recurrences were observed and the child is growing normally.

Figure 1. Chest X-ray showing right-sided pneumothorax in
a female neonate (Case 1).


The second case concerned a 12 year-old adolescent boy who was admitted to the emergency department,because of pain of sudden onset in the right hemithorax and dyspnoea. The patient was tall and thin, with a height of 178 cm, weight of 55kg and body mass index (BMI) of 17.4, at the 45th percentile for his age. According to his parents, he had no relevant past medical history. On physical examination, he had tachycardia (130ppm) and tachypnoea (20-24 breaths/min), diminished lung sounds and a tympanic sound on percussion of the right hemithorax. The heart sounds were normal with no murmurs and he had normal appearance of the chest, spine, pelvis, extremities and fingers, with none of the musculoskeletal malformations observed in Marfan’s syndrome. His visual acuity was normal. Plain chest X-rays were diagnostic for a right pneumothorax (Figure 2). A thoracostomy tube was inserted in the 6th intercostal space and connected with a closed drainage system. Chest high-resolution CT with 3-mm axial images failed to reveal blebs or bullae. Cardiac ultrasonogram was negative for valve disease or aortic malformations. The postoperative course was uneventful, the thoracostomy tube was removed in the 5th postoperative day and the patient was discharged after 6 days. Following discharge, ophthalmologic evaluation was normal and negative for lens ectopia, a clinical characteristic of Marfan’s syndrome. The family history included PSP episodes in the boy’s father and uncle (father’s brother), aged 49 and 52 years respectively. Both men had a tall, thin body pattern similar to that of the boy, with no musculoskeletal malformations. Plain X-rays and high-resolution CT of the chest were performed inboth men. The X-rays were normal, but both men had apical and lower segmental subpleural blebs demonstrated by CT (Figures 3 & 4). In order to exclude Marfan’s syndrome, both men underwent cardiac ultrasonogram and ophthalmologic evaluation, which were negative. No recurrence of PTX was observed in the adolescent during follow-up for 1.5 years.

Figure 2. Chest X-ray showing right-sided pneumothorax.


The third patient was a 16 year-old adolescent with a height of 185cm, weight of 65kg and BMI of 19, at the 25th percentile for his age. He had been a smoker of 8-12 cigarettes per day for the past 1.5 years. He presented in the emergency department complaining of right-sided chest pain and dyspnoea. His past medical history was negative for respiratory or other systemic disease, apart from myopia requiring the use of glasses from the age of 9 years. On physical examination the patient was severely dyspnoeic, with tachypnoea (18-20 breaths/min) with accessory respiratory muscle use, and tachycardia (145 ppm). The thorax had a normal appearance, the breath sounds were diminished in the right hemithorax and ipsilateral percussion produced a tympanic sound. The heart sounds were normal, with no murmurs. The spine was not scoliotic and the boy exhibited none of the musculoskeletal malformations observed in Marfan’s syndrome. The diagnosis of PTX was established with a plain chest X-ray. A thoracostomy tube was inserted in the 4th intercostal space and connected with a closed drainage system. Following drainage, the postoperative course was good, the thoracostomy tube was removed on the 5th day and the patient was discharged. Following discharge cardiac ultrasound and ophthalmologic evaluation were performed with normal findings except for the long-standing myopia. The family history was positive for PSP; the boy’s brother, aged 26 years had one similar incident 9 years earlier and his 41 year-old father reported two incidents at the ages of 19 and 24 years. All their PTX incidents had been treated with closed chest drainage. Both relatives shared the same tall, thin body stature, but with no musculoskeletal, cardiac or ophthalmologic history. The parents refused consent for chest CT in theboy, and both the brother and father declined chest CT for themselves and cardiac and ophthalmologic evaluations for the detection of possible diagnostic criteria of Marfan’s syndrome. During 9 months of follow-up, no recurrence of PTX was observed.

Figure 3. High-resolution CT showing apical blebs in the
father of an adolescent patient with PSP.
Figure 4. High-resolution CT showing lower lobe blebs in the
father of an adolescent patient with PSP.


Discussion


PSP is almost always associated with rupture of a subpleural microcystic lesion in the lung apex of patients with no underlying lung disease or history of trauma1-3. High-resolution CT imaging and thoracoscopy in patients with PSP usually reveals occult underlying lung anomalies in the form of blebs, bullae or larger cysts1,4,5. Blebs are defined as cystic lesions of <2cm with a well-defined wall, while bullae have a diameter of >2cm4. Such lesions are revealed in 100% of patients with PSP undergoing thoracotomy and 76% of those subjected to thoracoscopy6. Consequently, PSP is considered to be the clinical phenotype of an underlying disease equivalent to a form of peripheral acinar emphysema6-7.

The mechanism responsible for PSP includes rupture of subpleural blebs or bullae of the apical segment of the upper lobes or the superior segments of the lower lobes of the lung. The apical areas of the lung are subject to intense mechanical forces due to the presence of large alveoli and the relatively more intense negative intrapleural pressure. The formation of small lung cysts is caused by the rupture of alveoli and the diffusion of air into the interstitial lung tissue. The air then collects in the subpleural spaces, forming blebs and bullae. A proportion of these microcystic lesions is considered to be of congenital origin (familial spontaneous PTX), possibly due to collagen or connective tissue disorders, which are encountered either as part of specific syndomes, or as PTX episodes in the members of a family8-10.

The incidence of PSP in children is estimated to be 0.1%6. In adult series the frequency is estimated to be 7.4-18/10000 in males and 1.2-6/10000 in females, with a predisposition for tall, thin adolescents and young adults11-12.

PSP can affect neonates, accounting for 0.3-1.3% of all cases of neonatal respiratory disorders, causing respiratory distress, as in the first case described here13,14. Secondary SP is much more common in this age group and is usually secondary to respiratory distress syndrome, aspiration of meconium or blood, intense resuscitation efforts, positive airway pressures, lung hypoplasia, pneumonia or congenital cystic malformations. PSP in neonates is more common in premature babies and is very rarely familial13,14. Neonatal SP is believed to occur after alveolar rupture due to the high pressures required to inflate the lung or due to the asymmetrical distribution of inflation pressures amongst alveolar groups16. Conservative treatment with 100% oxygen and observation is usually adequate for the absorption of air leaks. However, in cases with large leaks and disturbances of the arterial blood oxygenation parameters (oxygen saturation, arterial blood gases), or in cases of tension pneumothorax, invasive treatment (needle thoracentesis or tube thoracostomy) is indicated. It has been estimated that in symptomatic neonates with PSP, surgical treatment was necessary in 7.5% of cases15.

After the neonatal stage, PSP is encountered almost exclusively in adolescence and young adult life. In a large adult series, the mean age at presentation was between 20 and 30 years, with a median age of 27 years16. PSP is almost always associated with subpleural emphysemalike lesions whose accurate incidence in the population is not known, and the correlation of these lesions with the appearance of PSP is still unclear. The risk of recurrence of PSP has been correlated with the number and size of these lesions, while their presence in the contralateral lung has been reported to be associated with a higher risk for PSP contralaterally17-19.

A number of theories have been proposed to explain the impressive correlation of sporadic and familial PSP with a specific somatic distribution, termed ectomorphy, consisting of tall stature, low weight and a flat chest, as seen in the adolescents and their affected relatives in this study, which are characteristics encountered in Marfan’s syndrome. According to one of the proposed theories, the rapid growth of the lung in relation to its vasculature, and the rapid growth of the vertical compared to the transverse dimension, affect the intrathoracic pressures and lead to apical segmental ischaemia and possibly to bleb and bullae formation9,20. Other authors have suggested alveolar inflammatory and fibrotic changes as the potential cause, while the observation that PSP is frequently accompanied by mitral valve proptosis (in up to 50% in some studies) along with other mesenchymal differentiation disorders, has led to the proposal of theories that include anomalies in collagen type I and III21.

Approximately 11.5% of patients with PSP have a positive family history for similar episodes22. The entity of familial spontaneous PTX (FSP) was first described in 1921 by Feber, and the association of PSP with a number of hereditary monogenic disorders has been well known for years10,17. These syndromes do not feature PSP as their main characteristic, but they should be included in the evaluation and differential diagnosis of patients presenting with PSP. Such disorders include Marfan’s syndrome, homocystinuria, Ehlers-Danlos syndrome, α1-antitrypsin deficiency, and Birt-Hogg-Dubι syndrome (table 1). Most families with PSP do not share common characteristics with these monogenic disorders, and currently the leading theory is that PSP is a separate entity in both clinical and molecular terms. The families of the adolescent patients described here belong in this category, as syndromic features were not observed in any members.

Two patterns of FSP inheritance have been proposed: a dominant autosomatic pattern with variable penetrance, and a sex-linked pattern22. Recently genetic research has revealed mutations in the Birt-Hogg-Dubι syndrome gene that encodes folliculin, in a large number of cases with familial PSP10,23,24. These cases can apparently be considered a part of the phenotypic spectrum (forme-fruste) of the Birt-Hogg-Dubι syndrome, which is a dominant autosomal disease characterized by skin lesions (fibrofolliculomas, trichodiscomas, and acrochordons), spontaneous pneumothorax and renal cancer of varying histological subtypes10. The majority of FSP cases cannot yet be attributed to Birt-Hogg-Dubι syndrome gene mutations, and the molecular basis of the disease, which can be considered a rare form of emphysema, is still to be defined. None of the patients and their relatives had skin lesions suspicious for Birt-Hogg-Dubι syndrome.

The treatment of PSP aims initially at lung re-inflation and secondly at prevention of recurrence.

Reinflation can be accomplished either by conservative means (i.e., observation with or without 100% O2 supplementation), or surgically, with thoracentesis, either needle aspiration, or closed chest drainage, when the pneumothorax is large (>50%) or under tension.



PSP in children has the tendency to recur more frequently than in adults2,25. The risk of recurrence following simple interventions is estimated to be between 16-52%, 60% after one recurrence and 80% after a second recurrence17,26. The risk for PSP in the contralateral lung is estimated to be 6-50% in most series17,27,28. In the three cases presented, no persistent air leaks were observed following thoracostomy tube drainage, and no recurrences occurred, but the duration of follow-up was no longer than 1.5 years. The methods used for the prevention of recurrence include: 1) Simple pleurodesis (induction of adhesions between the pleural surfaces in order to prevent re-accumulation of air) with chemical substances (tetracycline, silver nitrate, fibrin glue, talc) introduced via the thoracostomy tube; 2) Resection of the apical lung tissue which has microcystic lesions and pleurodesis either by chemical means or mechanically (i.e., pleurectomy, the removal of pleural surfaces or thermocoagulation ablation). This procedure can be accomplished either through an open thoracotomy (limited axillary thoracotomy in the 4th intercostal space – LAT), or thoracoscopically with or without video assistance (Video-assisted thoracoscopy – VATS).

Open thoracotomy is considered to be the most effective method, but is associated with significant morbidity. Improvement in thoracoscopic methods has established them as an alternative in the treatment of several thoracic diseases, including PSP. Current data suggest that VATS is associated with fewer early and late postoperative complications, scar formation and shorter hospital stay1,2,28. The disadvantages of VATS include prolonged operation duration, higher cost and possibly a slight increase in recurrence risk compared with LAT29-32. Pleurodesis has also been related with an increased risk of provoking a mild restrictive pneumonopathy33,34, but these disorders tend to improve with time and the overall prognosis is very good. Frequent PSP recurrence has led to the suggestion that all patients with PSP after the neonatal and infantile stages of life should be treated with thoracoscopy1,2,28. However, currently the usual strategy includes initial observation with supplemental 100% oxygen and drainage by thoracentesis or closed drainage if deemed necessary (respiratory distress, pneumothorax larger than 50% or pneumothorax under tension). Indications for thoracotomy or thoracoscopy include: persistent (>4 days) air leaks, PSP recurrences and possibly contralateral microcystic lung lesions1,35-38. Table 2 shows an algorithm for the treatment of spontaneous pneumothorax in children1,37.

The use of chest CT as a first-line imaging modality for evaluating PSP is also controversial. Plain chest X-rays are certainly adequate for imaging pneumothorax, but they fail to depict the underlying microcystic emphysematic anomalies that lead to PSP, for which their sensitivity is estimated to be 15%9. High resolution CT, with axial images of at least 3 mm, produces very detailed images of emphysematic lesions, identifying up to 88% of blebs and bullae observed during operation9,17. It is not yet clear whether the presence of emphysematic lesions is an indication for surgery, and if there is a possible correlation between emphysematic lesion size and recurrence risk. In addition, the capability of chest CT to determine which patients with contralateral microcystic disease would benefit from surgery is still unclear4,9,36.



As in simple cases of lung emphysema, PSP episodes are related to the quantity and duration of smoking. The second adolescent in this study had already been a smoker of approximately 10 cigarettes per day for 1.5 years, which possibly led to the earlier appearance of PSP, and relatives who had suffered PTX incidents were both smokers. The relative risk for PSP rises 7-fold for smokers of 1-12 cigarettes per day, 21-fold for 12-22 cigarettes per day and 80-fold for more than 22 cigarettes per day10, 38.

Conclusions


PSP is almost always associated with underlying subclinical emphysematic lesions, blebs, bullae or larger cysts, in the apical segments of the lung. In childhood, the disease mainly affects tall, thin, ectomorphic adolescent boys, but it is also observed in neonates, especially premature infants. The disease is usually sporadic, but familial cases account for up to 10%. Efforts to decipher the genetic identity of the disease have intensified recently, and specific pathologic gene alleles have been identified, such as that for the Birt-Hogg-Dubι syndrome. Treatment of PSP usually consists of drainage with thoracostomy tube placement, while more invasive procedures such as thoracotomy or thoracoscopy with resection of pathologic lung parenchyma and pleurodesis, aim at treatment and at the prevention of PSP recurrences, which are frequent (16-52%).

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