but of the cases reported in the literature , only a few ( three ) were preceded by vomiting [ 3 , 4 , 12 ] . so , there has to be another cause placing patients with an at risk for spontaneous pneumomediastinum . we report one case with spontaneous pneumomediastinum as the presenting symptom of an . in the other case , a review of the literature is given and we discuss the possible pathophysiology of spontaneous pneumomediastinum in patients with an . a 13-year - old girl presented with increasing complaints of an unusual crackling sensation and sound in her neck during three days . at that time further medical history mentioned a cooper test , a test of physical fitness , at school two weeks earlier . physical examination showed a respiratory rate of 16 per minute , cardiac rate of 51 per minute , blood pressure of 87/55  mmhg and temperature of 36.5c . her height was 150  cm ( sd 2 ) , weight 34  kg ( sd 1.5 ) and body mass index ( bmi ) 15  kg / m ( sd 2.5 ) . there was a slight bilateral bulging of the skin of her neck from the mandible to both clavicles , with , on palpation , a crackling sensation as a diagnostic sign of subcutaneous emphysema . apart from being extremely slim , the skin was normal , with no signs of injury . chest x - ray and computed tomography ( ct ) scan revealed mediastinal emphysema with extension to the neck region ( fig .  1 ) . after admission to the hospital , she showed loss of appetite and further history revealed an anorectic episode , for which , she had been referred by her general practitioner to a psychologist . at the age of 13  years , she weighed 46  kg , diminishing to 37  kg 4  months later . at the time of admission to the hospital , her weight was 34  kg at the age of 13  years and 6  months . 1coronal computed tomography ( ct ) reconstruction with mediastinal emphysema and subcutaneous emphysema in both axillas and lower neck regions in patient 1 with anorexia nervosa ( an ) coronal computed tomography ( ct ) reconstruction with mediastinal emphysema and subcutaneous emphysema in both axillas and lower neck regions in patient 1 with anorexia nervosa ( an ) within a week , the subcutaneous emphysema disappeared . she never showed any signs of purging during treatment and recovered from her an . a 17-year - old girl with known an and vomiting presented with extreme malnutrition requiring refeeding . she complained of unusual crackling sensation in her neck during eight days , starting after a choking incident while drinking , followed by coughing . the same day , she felt pressure on her chest . during the following days , her neck became swollen and her voice became hoarse . physical examination showed an extreme cachectic girl of 17  years with a respiratory rate of 16 per minute , cardiac rate of 64 per minute , blood pressure of 85/55  mmhg and temperature of 36.0c . her height was 170  cm ( sd=0 ) , weight 34.4  kg ( sd<<2 ) and bmi 12  kg / m ( sd<<2.5 ) . chest x - ray and ct scan revealed subcutaneous emphysema in the neck and mediastinal emphysema with extension to the intra - abdominal , retroperitoneal and epidural regions ( fig .  2 ) . 2chest ct showing epidural pneumatosis ( arrow ) in patient 2 with pneumomediastinum and an chest ct showing epidural pneumatosis ( arrow ) in patient 2 with pneumomediastinum and an laryngopharyngoscopy did not reveal mucosal lesions . after refeeding , she was referred to an eating disorders clinic to manage her eating disorder . within two weeks a 13-year - old girl presented with increasing complaints of an unusual crackling sensation and sound in her neck during three days . at that time further medical history mentioned a cooper test , a test of physical fitness , at school two weeks earlier . physical examination showed a respiratory rate of 16 per minute , cardiac rate of 51 per minute , blood pressure of 87/55  mmhg and temperature of 36.5c . her height was 150  cm ( sd 2 ) , weight 34  kg ( sd 1.5 ) and body mass index ( bmi ) 15  kg / m ( sd 2.5 ) . there was a slight bilateral bulging of the skin of her neck from the mandible to both clavicles , with , on palpation , a crackling sensation as a diagnostic sign of subcutaneous emphysema . apart from being extremely slim , the skin was normal , with no signs of injury . chest x - ray and computed tomography ( ct ) scan revealed mediastinal emphysema with extension to the neck region ( fig .  1 ) . after admission to the hospital , she showed loss of appetite and further history revealed an anorectic episode , for which , she had been referred by her general practitioner to a psychologist . at the age of 13  years , she weighed 46  kg , diminishing to 37  kg 4  months later . at the time of admission to the hospital , her weight was 34  kg at the age of 13  years and 6  months . 1coronal computed tomography ( ct ) reconstruction with mediastinal emphysema and subcutaneous emphysema in both axillas and lower neck regions in patient 1 with anorexia nervosa ( an ) coronal computed tomography ( ct ) reconstruction with mediastinal emphysema and subcutaneous emphysema in both axillas and lower neck regions in patient 1 with anorexia nervosa ( an ) within a week , the subcutaneous emphysema disappeared . a 17-year - old girl with known an and vomiting presented with extreme malnutrition requiring refeeding . she complained of unusual crackling sensation in her neck during eight days , starting after a choking incident while drinking , followed by coughing . the same day , she felt pressure on her chest . during the following days , her neck became swollen and her voice became hoarse . physical examination showed an extreme cachectic girl of 17  years with a respiratory rate of 16 per minute , cardiac rate of 64 per minute , blood pressure of 85/55  mmhg and temperature of 36.0c . her height was 170  cm ( sd=0 ) , weight 34.4  kg ( sd<<2 ) and bmi 12  kg / m ( sd<<2.5 ) . chest x - ray and ct scan revealed subcutaneous emphysema in the neck and mediastinal emphysema with extension to the intra - abdominal , retroperitoneal and epidural regions ( fig .  2 ) . 2chest ct showing epidural pneumatosis ( arrow ) in patient 2 with pneumomediastinum and an chest ct showing epidural pneumatosis ( arrow ) in patient 2 with pneumomediastinum and an laryngopharyngoscopy did not reveal mucosal lesions . after refeeding , she was referred to an eating disorders clinic to manage her eating disorder . within two weeks pneumomediastinum , the presence of free air contained within the mediastinum , usually results from spontaneous alveolar wall rupture and , far less commonly , from disruption of the upper airways or gastrointestinal tract . spontaneous pneumomediastinum can be distinguished from pneumomediastinum secondary to traumatic events , such as chest trauma or thoracic surgery , endobronchial or oesophageal procedures , mechanical ventilation or other invasive procedures . a large and diverse group of factors has been implicated in the development of spontaneous pneumomediastinum . various respiratory manoeuvres that have in common the development of high intrathoracic pressures may lead to pneumomediastinum . the mechanism of development of spontaneous pneumomediastinum was originally described by macklin and macklin as increased intra - alveolar pressure causing the rupture of alveoli with the escape of air into the mediastinum . the mediastinum is subsequently decompressed by further passage of the air into the retroperitoneal and subcutaneous spaces ( the macklin effect ) [ 1 , 9 ] . whereas primary pneumomediastinum is a relatively benign and self - limited disorder , secondary pneumomediastinum due to oesophageal perforation or boerhaave s syndrome is a potentially life - threatening disorder because of the inevitable development of mediastinitis . primary pneumomediastinum rarely requires treatment as the alveolair rupture heals and the leaked air resolves spontaneously . pneumomediastinum typically manifests as sudden chest pain or dyspnoea and , less commonly , with dysphagia and hoarseness . our first patient , however , presented with a sore throat , painful swallowing , complaints of pain in the neck and headache . the second patient presented with initial chest pain and hoarseness . the detection of subcutaneous air in the neck and anterior chest wall and hamman s sign , a crunching sound synchronous with the heartbeat , are important physical findings . radiographically , pneumomediastinum manifests on the posteroanterior projection as a thin radiolucent line parallel to the outline of the heart , as the mediastinal pleura is displaced laterally , and on the lateral projection as the accumulation of air retrosternally . panic disorders are often seen in patients with an . as a consequence , we believe that pneumomediastinum should be ruled out in anorexia patients presenting with signs of a first panic attack . purging behaviour , such as self - induced vomiting , is common among an patients . vomiting is a known cause of pneumomediastinum , placing anorexia patients , who frequently vomit , at risk for pneumomediastinum . however , in only a few of the cases described in the literature was vomiting was the preceding event of the pneumomediastinum . in most reports , like in our patients , pneumomediastinum in anorectic patients is not preceded by vomiting [ 1 , 2 , 4 , 5 , 7 , 8 ] . in our patients , the pathophysiologic mechanism of air entrance into the mediastinum can be explained by the rupture of an alveolar wall , which is mostly the cause of an air leak into the mediastinum . based on the literature and our observations , patients with an are at risk for spontaneous pneumomediastinum , even if they are not vomiting . animal studies reveal that calorie restriction causes a loss of alveoli and a fall in gas - exchange tissue [ 10 , 11 ] and thinner alveolar walls . to survive periods of not eating , organisms sacrifice comparatively non - essential structures for gluconeogenesis to provide glucose for the brain and amino acids to maintain muscle . because the total organismal and lung oxygen consumption fall during calorie restriction , some lung tissue is expendable . also in human studies , atrophic changes , such as large alveoli and thin alveolar walls , due to starvation were found in jewish people in the warsaw ghetto . with thinner alveolar walls and the loss of alveoli , since known factors of increased intra - alveolar pressure were absent in our first case and since clinical examination and radiographic study did not reveal an esophageal or upper airway perforation , we must assume that subclinical alveolar leaks with subsequent air dissection , pneumomediastinum and diffuse soft tissue emphysema occurred because of weakness of the alveolar wall and thinning of the connective tissue caused by severe malnutrition . therefore , even with a minimal increase of intra - alveolar pressure , such as that which may occur during usual daily activities , such as a choking incident , can become the cause of air leaks , as in our second case .
spontaneous pneumomediastinum is uncommon in paediatric practice . 
 we describe two cases of spontaneous pneumomediastinum in a child and an adolescent with anorexia nervosa . 
 thorough investigation failed to reveal any underlying cause for secondary pneumomediastinum . 
 pneumomediastinum in anorexia nervosa can be caused by not only elevated intrathoracic pressures , but also by the poor quality of the alveolar walls due to malnutrition . 
 the incidence of spontaneous pneumomediastinum in anorexia nervosa is probably higher than that recorded , since it resolves spontaneously and , therefore , it can remain undetected . 
 we conclude that it is our considered opinion that malnutrition associated with anorexia nervosa predisposes for spontaneous pneumomediastinum due to weakness of the alveolar wall and the loss of connective tissue .