a 15-year - old 
 boy was admitted to the emergency room with anterior chest pain , nonproductive 
 cough , progressive dyspnea , and subcutaneous emphysema of the neck .
all 
 symptoms had occurred suddenly , although the night before and the morning of the acute respiratory distress he had experienced heavy breathing , for which he 
 had arbitrarily taken oral corticosteroids .
he denied accidental trauma of the 
 chest , surgical maneuvers , or acute infections prior to the respiratory event . 

, 
 he was eupnoic at rest , respiratory rate was 18/min , oxygen saturation was 98% 
 on room air , pulse rate was regular , blood pressure was 110/60  mm  hg , and body 
 temperature was 36.5c .
physical examination revealed extensive subcutaneous 
 crepitations along the neck region and the superior part of the rib cage . 

laboratory studies revealed hb 15.7  gr / dl , and wbc counts11.2  10/l ( neutrophils 92.7% , lymphocytes 6.7% , and eosinophils 
 0.1% ) .
the patient 
 was referred for posteroanterior and lateral chest x - ray ( figures 1(a ) and 1(b ) ) , which 
 demonstrated linear streaks of air in the mediastinum extending into the upper 
 parts of the lung , more evident in the lateral projection .
the radiological signs of 
 pneumomediastinum are multiple and include radiolucent linear streaks of air in 
 the mediastinum , often extending into the neck , air surrounding the mediastinal 
 structures ; the presence of subcutaneous emphysema of soft tissues is often 
 described .
the lateral view increases the sensitivity in detecting signs of 
 pneumomediastinum , in that , it may reveal radiolucent bands in the retrosternal 
 areas , such as in our patient . for further evaluation ,
he underwent thoracic 
 high - resolution computed tomography ( hrct ) , where air was demonstrated 
 around the esophagus , trachea , ascending aorta , peribronchial , and perivascular 
 connective tissue ; partial pneumothorax on both sides was detected ; this was 
 more prominent at the level of the left apex of the lung . finally , diffuse 
 subcutaneous emphysema was present .
no other 
 abnormalities of the bronchial tree , such as fistulae , were detected .
the patient was treated with systemic and inhaled corticosteroids plus inhaled long - acting bronchodilators ; analgesic treatment was administered when necessary . a follow - up ct scan performed one week after the admission 
 showed almost complete resolution of the radiological alterations .
the patient 
 was discharged with no medication and was strongly advised to maintain a 
 resting lifestyle .
he was invited to return to the outpatient clinic for 
 follow - up investigations . at the 
 follow - up visits , he was asymptomatic , and physical and radiological 
 examinations were normal .
however , his mother reported an episode of acute dyspnea 
 when he was 4 years 
 old . in the year before the event
, he had suffered from frequent episodes of 
 rhinorrea , sneezing , nasal blockage , and sometimes chest tightness , especially 
 during exposure to pets and/or windy weather .
skin prick testing was performed , 
 revealing sensitivities to dermatophagoides pteronyssinus and farinae , grass 
 pollen , and dog dander .
total ige were 146  iu / ml ; specific ige for dermatophagoides 
 pteronyssinus and farinae was 0.470 
ku / l and 13.9  ku / l , respectively ; ige 
 values for dog dander were 11.3  ku / l , and for grass pollen 4.9  ku / l ( normal 
 range for specific ige < 0.10  ku / l ) .
spirometry documented significant 
 improvement in lung function after short - acting bronchodilator ( 15% from 
 baseline fev1 ) , which allowed for the diagnosis of asthma to be 
 made .
the diagnosis 
 of asthma is rarely a challenge for physicians ; usually , a suspicion arising 
 from the clinical manifestations of the disease is supported by the results of 
 the functional pulmonary tests showing signs of reversible bronchial 
 obstruction , which render the diagnosis an uncomplicated task . in some 
 circumstances , however , the diagnostic process may be delayed or influenced by 
 unusual presentation of asthma .
this occurs especially in elderly patients , in 
 whom multiple respiratory symptoms may be confusing or in subjects with 
 noncharacteristic symptoms , in whom the single respiratory symptom may be 
 misleading . in our case , 
 pneumomediastinum and pneumotorax represented the first presentation of 
 allergic asthma .
atypical presentations of asthma have been associated with 
 cough as the only respiratory symptom ( cough - variant asthma ) ; 
 urticaria   or anaphylactic shock   is known as first 
 appearance of an underlying asthma .
pneumomediastinum has been reported as an 
 unusual , rare complication of bronchial asthma [ 4 , 5 ] .
reports on this 
 topic are scarce and all refer to spontaneous pneumomediastinum and 
 subcutaneous emphysema following an acute attack of asthma . to our knowledge , 

this is the first clinical report of pneumomediastinum as initial sign of 
 undiagnosed asthma .
on the basis of the documented sensitization to grass 
 pollen in our patient , and given that the episode occurred in september when 
 the pollen concentration is still elevated in southern italy , the role of the 
 allergic component as the precipitating factor can not be excluded .
the air leakage is 
 usually the result of alveolar wall rupture secondary to high intra - alveolar 
 pressures .
histological studies   have shown that air dissects into 
 the connective tissue , resulting in interstitial emphysema . because of a 
 pressure gradient between the periphery of the lung and the hilus , air tracks 
 along the vascular sheath into the hilum , thus reaching the mediastinum and 
 moving to the neck and the subcutaneous space . sometimes , air may also 
 decompress into the pericardium or retroperitoneal tissues .
causes of increased 
 alveolar pressure include barotrauma in patients receiving mechanical 
 ventilation , deep inspiratory maneuvers such as during strenuous exercise or 
 diabetic ketoacidosis , extreme respiratory efforts such as violent cough or 
 prolonged valsalva manoeuver , and obstructed expiratory flow with 
 overinflation .
the clinical description of our patient leaves no doubt on the 
 obstructive origin of the pneumomediastinum .
asthma has been described in 
 different studies as a predisposing factor for the development of spontaneous 
 pneumomediastinum in up to 50% of cases [ 710 ] .   in the retrospective study of macia
9 
 out of 41 patients ( 22% ) had a recent of remote history of asthma , and a severe 
 attack precipitating the pneumomediastinum was demonstrated in only one out of 
 four asthmatics .
nonrespiratory causes of pneumomediastinum are represented by 
 disruption of the esophagus , penetrating thoracic injuries , or mediastinal 
 infection with gas - forming bacteria . the clinical history and the absence of 
 symptoms suggestive of the above - described conditions in our patient allowed ruling out nonrespiratory 
 causes of the pneumomediastinum .
the incidence 
 of spontaneous pneumomediastinum is difficult to establish due to the paucity 
 of studies [ 11 , 12 ] .
the clinical diagnosis is based on the symptom 
 triad of dyspnea , nonspecific chest pain , and subcutaneous emphysema , which was 
 evident in our case .
however , symptoms are nonspecific , and sometimes the 
 patient may be asymptomatic . the only patognomonic sign ( hamman 's sign ) ,   characterized by a crunching or bubbling sound that is synchronous with the 
 heart beat , is rarely noticed by the patient or the physician . in a revision of 
 41 cases with pneumomediastinum , hamman 's sign was detected in only 12% of 
 patients .
our patient only referred progressive dyspnea and chest 
 pain ; no other respiratory and nonrespiratory symptoms were present ; hamman 's 
 sign was not detected at the time of presentation .
the computed 
 tomography ( ct ) scanning is considered the gold standard of imaging tests 
 because it is able to detect even small amounts of mediastinal air .
the ct scan 
 has the advantage over the chest radiographs of offering superior contrast 
 resolution and lack of superimposition ; therefore , the sensitivity of the 
 methodology is greater , enabling the false negative cases to be reduced . in our 
 case , the ct scans allowed to detect the initial condition and to follow the 
 clinical and radiological evolutions .
in addition to 
 the evaluation and treatment of the underlying condition , the typical 
 management of pneumomediastinum consists of rest , oxygen therapy , and 
 analgesia . our patient was treated with bed rest and analgesics ; oxygen and 
 cough sedatives were not required .
after the discharge , he was strongly invited 
 to follow a rigid resting lifestyle , and asthma was treated according to the most 
 recent guidelines . in conclusion , 

pneumomediastinum with pneumothorax and subcutaneous emphysema may represent a 
 very unusual presentation of underlying allergic asthma .
pneumomediastinum is a 
 benign condition , which occurs spontaneously or as a complication of an 
 underlying respiratory disease , such as during an asthma attack .
this is , to 
 our knowledge , the first report of pneumomediastinum as asthma symptom , rather 
 than asthma complication . in the diagnostic evaluation of the causes of 
 pneumomediastinum in young subjects , the presence of underlying asthma
 we describe the case of an adolescent who was admitted to the hospital because of sudden occurrence of chest pain , dyspnea and subcutaneous emphysema . on admission , 
 physical examination revealed subcutaneous crepitations in the superior part of the rib cage , and auscultation of the chest showed widespread wheezing . 
 the radiological assessment confirmed the diagnosis of pneumomediastinum and pneumothorax . a follow - up ct scan performed one week after the admission showed almost complete resolution of the radiological alterations . at the following visits , 
 the patient was asymptomatic , but reported to have suffered from frequent episodes of rhinorrea , sneezing , nasal blockage , and sometimes , chest tightness , especially during exposure to pets and/or windy weather .   
 skin prick testing showed sensitivities to dermatophagoides pteronyssinus and farinae , grass pollen and dog dander . 
 spirometry documented significant improvement in lung function after short - acting bronchodilator , allowing for the diagnosis of asthma to be made . 
 although pneumomediastinum may be a complication of various respiratory diseases , including asthma , it has never been reported as the first presentation of underlying bronchial asthma . 
 herein , the physiopathological mechanisms , the diagnostic procedures and treatment of pneumomediastinum in asthma are discussed . 
 we suggest that the diagnosis of asthma should be considered in the differential diagnosis of pneumomediastinum in adolescence . 
1. Case Report
2. Discussion