acute fibrinous and organizing pneumonia ( afop ) was first described by beasley et al . in 2002 as a condition characterized by alveolar damage , eosinophilic pneumonia , and organizing pneumonia . the features that distinguish it histologically are the presence of intra - alveolar fibrin balls , absence of usual hyaline membranes and eosinophils and many foci of fibroblastic activity . it has been described in almost all age groups with associations including autoimmune disease and connective tissue , drugs , occupational , and environmental exposures and other infectious agents . they are usually two forms of this illness , a severe form which leads to rapid respiratory failure and a subacute form which has a much better prognosis . there is no specific treatment though immunosuppressant and steroids produce good results in patients with sub - acute afop . the chest radiograph findings of afop are almost identical to those seen in cryptogenic organizing pneumonia , consistent with migratory , patchy , diffuse , alveolar opacities with bilateral , and peripheral distributions . a 42-year - old female was admitted with complaints of dry cough of 5 days , high - grade fever since 15 days , generalized malaise and progressive worsening shortness of breath since 5 days . no known chemicals , fumes or occupational or allergen exposure . upon examination , she was dyspneic , blood pressure of 110/70 mmhg and had fever of 103 f. she had a respiratory rate of 32/min , heart rate of 120 beats / min . she had no icterus , edema , clubbing , rash , skin lesions , cervical lymphadenopathy , or joint swelling . her arterial blood gas ( abg ) analysis revealed ph of 7.47 , pco2 of 41 mmhg , and po2 of 39 mmhg . chest radiographic findings showed inhomogeneous bilateral opacification in lower lung zones . the rest of the laboratory tests , including liver function test , kidney function test , coagulation profile , urine examination , etc . work up of anti - nuclear antibodies , angiotensin converting enzyme , dsdna antibodies , antinuclear and cytoplasmic antibodies , rheumatoid arthritis factor , extractable nuclear antigen profile , and anti - phospholipid anti bodies were negative . she was initially treated with noninvasive ventilation , oxygen therapy , antibiotics such as combination antibiotic regimen with pipercillin - tazobactam with and clarithromycin . high - resolution computed tomography ( hrct ) thorax revealed bilateral diffuse confluent consolidation in lower lung zones [ figure 1a  c ] . bronchoscopy followed by bronchoalveolar lavage ( bal ) was performed ( gene xpert real - time pcr ) . transbronchial lung biopsy was performed from the right lower lobe , biopsy report of which came out to be afop [ figure 1d and e ] . she was treated with 40 mg prednisolone twice daily along with bronchodilators and oxygen therapy . her abg also improved significantly with po2 at 92 mmhg and her saturation at 95% . she was initially on high flow oxygen mask which came down to minimum level and eventually she did not require any oxygen therapy after 5 days of steroid therapy initiation . ( a ) axial and ( b ) cornal computed tomography through lungs : geographical distribution of widespread consolidation with ground glass opacities and septal thickening in both lungs . ( c ) axial computed tomography taken after 15 days after treatment : resolution of large component of organizing consolidation with residual ground glass opacities and mild septal thickening . ( d and e ) intra - alveolar fibrin in the form of  fibrin balls  without formation of hyaline membranes ( h and e , 100 ) afop has been reported in all age groups with average age being 62 years originally described by beasley et al . it has been reported that afop may occur as an idiopathic variety or in association with clinical conditions , including collagen vascular diseases , drug reactions , occupational or environmental exposures , as well as various infections . retrospective follow - up of these patients shows two varieties of progression . a subacute variety and a severe variety which usually leads to respiratory failure and the prognosis of the severe variety is not promising . on average , severe form of afop this variety seems to resemble cryptogenic organizing pneumonia ( cop ) in terms of prognosis and recovery following corticosteroid treatment . afop has been described with many other conditions in the past while twelve reported cases were idiopathic . therefore , there could be an association between autoimmune disease and afop . in our case , there was no evidence of malignancy or any other factors known to be related with pneumonia . however , lung biopsy revealed that the patient has unusual histological pattern that was identified as afop . nevertheless , it is important to note that sub - acute forms of this disease seem to be mistaken for cop . therefore , histological diagnosis is essential for distinguishing the two through ct - guided or bronchoscopic biopsy . the most commonly used methods to obtain a tissue sample include video - assisted thoracoscopic biopsy and a ct - guided biopsy . diagnosis of afop in indian case reports has been achieved through ct guided biopsy followed by treatment of the disease by prednisolone . she required intensive care support for 5 days eventually being discharged home after 10 days of hospitalization . by this study , we suggest that afop should be taken into consideration and differential diagnosis of severe acute pneumonias with no significant co - morbidities . diagnosis is mostly biopsy proven , and treatment through corticosteroids is quite promising .