lipoid pneumonia ( lp ) is a rare inflammatory disease of the lung parenchyma caused by accumulation of fatty oily material in the alveoli .
exogenous lipoid results from aspiration or inhalation of mineral , vegetable , or animal oil into the peripheral lung .
children can aspirate large amounts of different oily materials , mineral oil being the most frequently encountered substance , and this happens especially when certain risk factors are present .
the aspiration of fatty material elicits a pulmonary inflammatory reaction that produces non - specific clinical and radiologic findings , often similar to those of bacterial pneumonia and tuberculosis , complicating or delaying the diagnosis .
thus , it is imperative to identify correctly this entity when there is a high degree of suspicion , through a thorough and focused noting of patient 's medical history and an accurate recognition of its radiologic manifestations .
we present a case of acute lp in a 5-month - old infant due to accidental mineral oil aspiration , confirmed by analysis of bronchoalveolar lavage ( bal ) and focus on the radiologic findings showing evolution of parenchymal lesions over a follow - up period of 7 years .
this was a case report of a 5-month - old male infant who was admitted as an emergency case to a secondary care hospital with acute onset of high - grade fever and respiratory distress .
the chest x - ray showed bilateral extensive consolidation involving mainly the lower lobes of the lungs .
he was placed on broad spectrum antibiotics and bronchodilatory inhalers , in response to which he showed no clinical improvement over a period of 2 days . therefore , and in view of his deteriorating clinical status , he was urgently transferred to our hospital for further management . upon arrival ,
the infant was in respiratory distress requiring 4 l / min of oxygen to keep his oxygen saturation above 90% .
further examination of the infant revealed dysmorphic features such as low set ears , generalized muscular hypotony , and delayed psychomotor development .
additional questions on patient history identified that at the age of 5-months the child had accidentally ingested paraffin oil administered by his 3-year - old brother .
computed tomography ( ct ) scan [ figure 1a ] revealed extensive bilateral consolidations in the lower lobes .
the bal aspirate was opalescent with a supernatant halo of fat and showed an increased number of macrophages .
bal was sent for microbiological studies including gram staining , ziehl - neelsen staining , and bacterial and fungal cultures .
the cytologic study showed numerous foamy macrophages with intracytoplasmic and extracellular droplets of fat with a positive histochemical confirmation of acute lp with oil red o stain .
( oil red o is a fat - soluble dye used for staining of lipids and triglycerides . )
total lavage was not performed as it was considered too risky in view of the critical status of the patient and the signs of hypoxia he demonstrated during the procedure .
5-month - old male infant aspirated large amounts of paraffin oil causing respiratory distress diagnosed later as due to lipoid pneumonia ( a ) chest computed tomography ( ct ) performed 1.5 month post - paraffin oil aspiration shows diffuse extensive airspace consolidations ( arrows ) in both lower lobes .
( b ) high - resolution chest ct taken 7 months after the incident shows persistent imaging findings ( arrows ) with minimal improvement .
a corticosteroid therapy regimen was introduced which led to an improvement of his general condition .
the infant remained in our hospital for a total of 5 months showing gradual clinical improvement . before discharge
an additional bronchoscopy and bal was performed that showed a clear aspirate with no supernatant fat and fewer lipid - laden macrophages .
further , an additional ct scan was performed which showed persistent findings with minimal improvement [ figure 1b ] .
he underwent spirometry , which revealed a forced vital capacity ( fvc ) equal to 85% of predicted value , a forced expiratory volume in 1 s ( fev1 ) of 79% of predicted value .
fev1/fvc ratio was 81% , which was within the normal range ( approximate range : 75 - 80% ) for healthy adults .
the patient could not undergo further pulmonary function testing ( lung volume , diffusing capacity of lung for carbon monoxide ) .
bal revealed far fewer lipid - laden macrophages , while the ct scan showed resolution of the consolidations , but evidence of residual interstitial findings [ figure 2 ] .
follow - up high - resolution chest computed tomography taken 7-years after the episode of aspiration , shows bilateral thickening of the interlobular septa ( open arrow ) , streaky peripheral infiltrates ( arrows ) and areas of hyperinflation .
lp is an uncommon pulmonary disorder that results from the accumulation of lipids in the alveoli . on the basis of the source of the lipid
the exogenous type is due to aspiration of animal fat , vegetable or mineral oil and can be acute or chronic in presentation .
acute exogenous lp is a type of pneumonitis associated with an incident of aspiration of a large amount of an oil - based product .
most cases of exogenous lp result from aspiration of mineral oil , which is usually used for the treatment of refractory constipation . in early childhood ,
the factors that increase the risk of aspiration , in both the acute and chronic form , are commonly associated with underlying conditions , such as disruption of the normal physiologic function of the airway and the upper gastrointestinal tract , congenital disorders of the structure and function of the foregut , and impairment of neurologic or neuromuscular control of the process of breathing and/or swallowing .
additional predisposing factors to lp in children are gastroesophageal reflux and forced ingestion of oily medication as practiced in a number of geographic areas .
our patient showed features of developmental delay along with generalized muscular hypotony , which was hypothesized to have contributed to the aspiration of a large amount of material .
acute exogenous lp in children , typically manifests clinically as an acute aspiration condition , which evolves into respiratory failure and , occasionally , death . in the report published by zanetti et al .
, 17 children with lp having non - specific clinical presentation , showed air space consolidation on chest radiographs , which suggested bacterial pneumonia .
the children showed no improvement with antibiotic therapy and were later investigated with high - resolution ct and bal . only at this stage
the time period between the initial radiographs and diagnosis varied from 30 days to 45 days .
such a delay was also observed in our case , partially attributed to the initial reluctance of the parents to mention the incident of accidental aspiration , afraid of being accused of lack of proper care of the baby .
acute exogenous lp manifests radiologically within 30 min of the episode of aspiration or inhalation .
pulmonary opacities can be seen in most patients within 24 h. chest x - ray shows parenchymal abnormalities that include areas of ground - glass opacity or consolidation , bilateral and segmental or lobar in distribution and predominantly involving the middle and lower lobes , similar to those seen in general aspiration pneumonia .
high - resolution computed tomography is the imaging technique of choice for investigating lp and , in children , it must be performed with the lowest possible radiation .
the principal ct imaging findings include alveolar consolidations , ground - glass opacities , nodular lesions , interlobular septal thickening , and intralobular interstitial thickening .
the crazy - paving pattern , consistent with well - defined areas of ground - glass attenuation with superimposed septal thickening , has also been described as a characteristic feature of lp .
in addition , exogenous lp may be diagnosed promptly when areas of fat attenuation are identified within a pulmonary air - space consolidation .
pure mineral oil has a ct attenuation value of -132 hu and negative density values ( between -30 and -150 hu ) within the consolidation area .
these findings , although non - specific , can suggest the diagnosis of lp . however , in some patients with lp , as in the present case , fat attenuation is not evident on ct images because the fat attenuation values are averaged with the surrounding inflammatory exudates so that the fat component becomes less conspicuous or obscure .
according to most studies on pediatric patients , the radiologic manifestations of acute exogenous lp typically improve or resolve over time .
sias et al . , evaluated 28 children with lp for 24 months and demonstrated normalization of ct scans in 18 of them right after treatment . in two patients scanned 12 months after treatment , a cystic lesion in the right lung and a discrete area of segmented atelectasia
treatment abandonment occurred in 6 cases and no further ct follow - up was reported for the remaining children .
sias et al . , also demonstrated the potential role of multiple bals in the treatment of lp , in a prospective study of 10 children with lp . in these cases ,
lp was secondary to mineral oil aspiration , and the delay between aspiration and treatment was 1 - 60 days . over a follow - up period of 6 months , complete radiologic resolution was demonstrated in 3 out of 6 patients who had a short interval between intake of mineral oil ( 1 - 4 days ) and treatment . in the remaining three cases ,
all four children with a longer time interval between aspiration of mineral oil and treatment had residual areas of consolidations on ct scans taken at 6-months , but no further follow - up was reported . in our case , the follow - up ct scan that was performed 7 years after the aspiration demonstrated architectural distortion associated with thickening of the interlobular septa .
mineral oil ( a mixture of inert , long - chain , saturated hydrocarbons obtained from petroleum ) is emulsified and phagocytosed by alveolar macrophages , which , filled with oil , reach the interlobular septum through the lymphatic channels .
subsequently , with the permanence of the oil , there is development of chronic interstitial inflammation , which can evolve into pulmonary fibrosis and decreased lung volume . in our case
, there was no evidence of end - stage lung lesions and functional respiratory tests were normal .
the imaging findings can be attributed to the large amount of aspirated oil , the delay in the correct diagnosis and the fact that the patient did not undergo any therapeutic bal , which has been shown to facilitate the removal of lipid - laden macrophages implicated in development of alveolar and interstitial fibrosis . to the best of our knowledge , this is the longest follow - up study of a pediatric patient with acute lp showing imaging features on ct and the only case reported where a single episode of fat aspiration that is associated with residual interstitial changes in the follow - up ct scan .
we have described a case of acute exogenous lp induced by accidental aspiration of mineral oil for which the early imaging findings were consistent with published reports .
long - term follow - up , however , revealed partial resolution with persistent interstitial lesions seen on ct scan .
a finding that has not been reported in the pediatric population and merits consideration when interpreting imaging examinations of patients with a history of acute lp .
 acute lipoid pneumonia ( lp ) in children is a rare disorder caused by the aspiration of oil - based substances and is difficult to diagnose due to non - specific clinical symptoms and radiological findings . 
 we report the case of a 5-month - old male infant with acute lp caused by accidental aspiration of a large amount of mineral oil . 
 we present the imaging findings in the computed tomography scans performed during his hospitalization and focus on the residual abnormalities seen on a scan performed 7-years after the incident . 
 this , to the best of our knowledge , is the longest follow - up report of an acute exogenous lp patient and the only case that demonstrates non - resolving abnormalities in a pediatric patient after a single acute episode of mineral oil aspiration . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION