although s. pneumoniae is the most common cause of community - acquired pneumonia ( cap ) in many countries , there are considerable geographic differences in the incidence of other pathogens .
tuberculosis ( tb ) is often overlooked as a cause of cap , particularly when it presents as an acute illness ( 2 ) .
although the presentation of pulmonary tb as acute pneumonia is not unusual , its manifestation as acute respiratory distress syndrome ( ards ) is rare .
ards is a severe form of diffuse alveolar injury . the american - european consensus conference ( aecc ) ( 1994 )
defined ards as an acute condition characterized by bilateral pulmonary infiltrates and severe hypoxemia in the absence of evidence for cardiogenic pulmonary edema .
the severity of hypoxemia necessary to make the diagnosis of ards was defined by the ratio of the partial pressure of oxygen in the patient s arterial blood ( pao2 ) to the fraction of oxygen in the inspired air ( fio2 ) .
ards was defined by a pao2/fio2 ratio of less than 200 , and , in acute lung injury ( ali ) , by a ratio less than 300 ( 3 ) .
recently , a panel of experts redefined the definition ( berlin definition ) ( 2011 ) and categorized ards into three levels : mild ( pao2/fio2 200300 ) , moderate ( pao2/fio2 100200 ) , and severe ( pao2/fio2 100 ) ( 4 ) .
even though ali and ards are well recognized complications in patients with severe tb , such as miliary tb or tb bronchopneumonia , sparse epidemiological data are available on this entity .
most patients who develop ali / ards have underlying chronic medical conditions or hiv infections , and their diagnoses were delayed ( 5 )
. herein , we present a rare case of a previously healthy young patient with acute pulmonary tuberculosis in the form of tb pneumonia that was complicated by ards .
a 21-year - old woman , a radiology technician student , presented with acute respiratory failure due to progressive respiratory symptoms , including productive cough and dyspnea that started seven days before presentation . at the time of her admission to the hospital
her initial vital signs were as follows : bp = 110/70 mmhg , hr = 122/min , rr = 40/min , and temperature = 40 c .
lung examination revealed bilateral coarse crackles . because she presented during the influenza season and because the symptoms were compatible with severe pneumonia , a broad spectrum of antibiotics and oseltamivir were started , and she was intubated and received mechanical ventilation .
there was no history of previous illness or recent travel and no family history of note .
arterial blood gas revealed hypoxemia ( pao2 = 24.3 mmhg ) , hypercapnia ( paco2 = 55.1 mmhg ) , and respiratory acidosis ( ph = 7.25 , hco3 : 26 ) .
the hiv test was negative . based on an initial pao2/fio2 ratio of less than 100 on ventilator setting that included peep and characteristic diffuse bilateral infiltrates on chest x - ray ( figure 1 ) , acute respiratory distress syndrome ( ards )
bacterial and fungal cultures of respiratory secretions showed no growth after seven days . a real - time pcr test on respiratory specimens for influenza a and b was negative .
accordingly , diagnosis of ards secondary to pulmonary tuberculosis was made , and the patient received anti - tuberculous drugs and intravenous hydrocortisone 100 mg three times per day .
the patient continued to improve gradually during the first week , and she was successfully weaned and extubated on her seventh day in the hospital .
her chest infiltrates gradually resolved during the first week , but left lower- and mid - zone consolidation remained ( figure 3 ) .
she remained hospitalized in the infectious ward and received o2 therapy plus anti - tuberculous drugs for another 15 days .
corticosteroids were stopped . during this period she remained mildly tachypnic and hypoxic . on the 24 day after presentation , she was discharged with stable vital signs and no hypoxia in the room air .
a 21-year - old woman , a radiology technician student , presented with acute respiratory failure due to progressive respiratory symptoms , including productive cough and dyspnea that started seven days before presentation . at the time of her admission to the hospital
her initial vital signs were as follows : bp = 110/70 mmhg , hr = 122/min , rr = 40/min , and temperature = 40 c .
lung examination revealed bilateral coarse crackles . because she presented during the influenza season and because the symptoms were compatible with severe pneumonia , a broad spectrum of antibiotics and oseltamivir were started , and she was intubated and received mechanical ventilation .
there was no history of previous illness or recent travel and no family history of note .
arterial blood gas revealed hypoxemia ( pao2 = 24.3 mmhg ) , hypercapnia ( paco2 = 55.1 mmhg ) , and respiratory acidosis ( ph = 7.25 , hco3 : 26 ) .
the hiv test was negative . based on an initial pao2/fio2 ratio of less than 100 on ventilator setting that included peep and characteristic diffuse bilateral infiltrates on chest x - ray ( figure 1 ) , acute respiratory distress syndrome ( ards )
bacterial and fungal cultures of respiratory secretions showed no growth after seven days . a real - time pcr test on respiratory specimens for influenza a and b was negative .
accordingly , diagnosis of ards secondary to pulmonary tuberculosis was made , and the patient received anti - tuberculous drugs and intravenous hydrocortisone 100 mg three times per day .
the patient continued to improve gradually during the first week , and she was successfully weaned and extubated on her seventh day in the hospital .
her chest infiltrates gradually resolved during the first week , but left lower- and mid - zone consolidation remained ( figure 3 ) .
she remained hospitalized in the infectious ward and received o2 therapy plus anti - tuberculous drugs for another 15 days .
corticosteroids were stopped . during this period she remained mildly tachypnic and hypoxic . on the 24 day after presentation , she was discharged with stable vital signs and no hypoxia in the room air .
this case features a rare manifestation of pulmonary tuberculosis in a previously healthy young woman with acute presentation of tuberculous pneumonia complicated by ards .
tuberculous pneumonia is defined as nodular lesions resulting from air - space consolidation due to endobronchial spread to lobar or multilobar locations ( 5 ) .
m. tuberculosis is an important cause of community - acquired pneumonia ( cap ) in developing countries .
tb can present as an acute process and should be included in the differential diagnosis of cap .
it may mimic classic bacterial pneumonia or masquerade as an atypical pneumonia , with non - productive cough and systemic symptoms .
missed diagnosis is common , as illustrated in report from baltimore in which 16 of 33 patients ( 48% ) with culture - confirmed pulmonary tb were treated initially for presumed cap ( 1 ) .
the incidence of tb being diagnosed among patients presenting with clinical and radiological signs of a cap has varied in different series .
previously , studies from china , japan , kenya , and sub saharan africa also demonstrated high prevalence of pulmonary tb ( 920.5% ) in patients who presented with cap ( 611 ) .
m. tuberculosis was the second most common pathogen ( 12% ) identified in the study performed by levy et al .
, only patients who presented with features of acute pneumonia were included ; those with chronic illness or typical radiologic changes suggestive of tb were excluded .
a similar high incidence of tb ( 10% ) among subjects presenting with acute pneumonia was reported in france ( 7 ) .
although presentation of pulmonary tb as acute pneumonia is not unusual , its manifestation as ards is rare .
this complication is associated with a very high mortality ( 4080% ) despite treatment ( 5 ) . even in a large study from india that was conducted by agarwal et al
, tb accounted for only 4.9% of patients ( 9 of 187 ) who were admitted with a diagnosis of ards over a 7-year period , of whom two patients died .
the lower mortality rate in this study could be attributed to the fact that all subjects were started empirically on anti - tb therapy with the median time to initiation of therapy being three days .
tracheal aspirate sent for ziehl - neelsen staining did not indicate that there were acid - fast bacilli in any of the patients of this study ( 13 ) . in another study by sharma et al . in india , of 2,733 tb patients treated during 19802003 , 29 ( 1.06% , i.e. , 1.21 patients / year ) developed ards ( 14 ) .
another large retrospective study conducted by deng et al . in china over a five - year period ( 20062010 ) showed that , among 16,238 patients who were admitted to the respiratory departments with a diagnosis of pulmonary tb , 471 patients were diagnosed as having miliary tb , of whom 85 developed ards and were admitted to the icu during the study period .
the mortality rate in this study was 47.1% , and the mean duration of mechanical ventilation was 8.5  3.0 days in all patients ( 15 ) .
another study from south korea described 67 patients with ards caused by miliary tb admitted to the icu during 19992008 .
all - cause mortalities in the icu and the hospital were 58.2 and 61.2% , respectively . in their study ,
28.4% of the patients were older than 71 , but clinical outcomes in these patients did not differ significantly from outcomes in younger patients ( 16 ) .
( 17 ) found that higher psi scores were independently associated with the presence of concomitant pulmonary tb in both health care associated pneumonia ( hcap ) and cap patients . in the study performed by levy et al .
( 18 ) , the incidence rate of 1.5% was reported for acute respiratory failure among hospitalized patients who presented with tuberculous cap .
although ards invariably occurs in patients with severe tb , such as miliary tb or tb bronchopneumonia ( 5 ) , its occurrence in tuberculous pneumonia and cavitary pulmonary tb also was described ( 5 ) . in the study of agarwal et al .
, radiography of eight of nine patients with tb and ards revealed miliary nodules , and consolidation was observed in only one patient ( 13 ) .
seven out of 29 patients with tb and ards in the study of sharma et al . had pulmonary tb , and 22 had miliary tb ( 14 ) .
several predisposing factors for development of ards in tb patients and several prognostic factors in these patients have been described . according to the study of deng et al . , the duration of time to diagnosis , time from diagnosis to mechanical ventilation , and time to anti - tuberculosis therapy were significantly shorter in survivors than for non - survivors .
diabetes mellitus , increased ast , alt , and d - dimer , decreased hemoglobin , and albumin were found to be independent predictors of the development of ards in the setting of miliary tb ( 15 ) . in the study reported by sharma et al . , the presence of miliary tb , duration of illness beyond 30 days at presentation , absolute lymphocyte count less than 1625/mm and serum alt greater than 100 iu / l were independent predictors of the development of ards .
patients with apache ii scores > 18 , those with apache ii scores < 18 in the presence of hyponatraemia , and those with pao2/fio2 ratios < 108.5 were likely to die ( 14 ) .
showed that the sequential organ failure assessment ( sofa ) score on the day that ards is diagnosed is a valuable prognostic indicator ( 16 ) .
the case presented is special in its manifestation from several clinical perspectives , including lack of underlying medical condition or immune defect and development of ards in non - miliary and non - disseminated tuberculosis . in conclusion ,
the diagnosis of tb should be considered in all patients who present with cap in our region .
it has been suggested that , in a patient with unexplained ards , a history of fever of more than 15 days duration and elevation of serum alkaline phosphatase should arouse the suspicion of disseminated tb as the underlying cause ( 5 ) .
it also has been suggested that , in patients with ards of obscure etiology where the clinical features suggest tb as the inciting cause , anti - tb therapy should be started empirically , and the diagnosis actively pursued later ( 13 ) .
both primary and reactivation tb may present as an acute illness and mimic cap . as a result of the impressive mimicry of tb , the diagnosis must be considered , at least initially , in all cases of acute pneumonitis , especially in regions where tuberculosis is endemic .
 the presented case features a rare manifestation of pulmonary tuberculosis in a previously healthy young woman who had acute presentation of tuberculous pneumonia complicated by acute respiratory distress syndrome . in developing countries 
 , mycobacterium tuberculosis is an important cause of community - acquired pneumonia ( cap ) . 
 tb can present as an acute process and should be included in the differential diagnosis of cap . 
 this case is special in its manifestation from several clinical perspectives , including the lack of an underlying medical condition or immune defect and the development of acute respiratory distress syndrome ( ards ) in non - miliary and non - disseminated tuberculosis . in conclusion 
 , the diagnosis of tb should be considered in all patients who present with cap in endemic regions . 