Case 84. Pneumocystosis (3 y-o M)
         
    Fatal interstitial pneumonia after chemotherapy for disseminated adrenal neuroblastoma    
         
   
Key words : Pneumocystis carinii, interstitial pneumonia
   
         
   
opportunistic infection
   
     
 
     
Diffuse consolidation of the lung parenchyma is characteristic of acute interstitial pneumonitis (gross findings after formalin fixation).   Frothy exudates into the alveolar pace are pathognomonic of pneumocystosis (HE). Septal thickening and swelling alveolar pneumocytes are associated.
     
 
     
The cyst wall of P. carinii in the frothy exudates is stained black by Grocott's silver. The cysts themselves are not recognizable in H&E preparations.   Grocott-stained cysts in a paraffin section were observed at the ultrastructural level. In addition to the cyst wall, so-called parenthesis-like structure inside the cyst shows argyrophilia. The cyst is often crescent in shape.
     
 
     
Reference case 84A
Pneumocystis carinii in bronchial lavage from an AIDS patient (Papanicolaou). In Papanicolaou-stained preparation, the cysts of P. carinii resemble lysed red blood cells.
  Reference case 84A
Pneumocystis carinii in bronchial lavage from an AIDS patient (Grocott). The cyst wall of the microbes is stained by Grocott's silver. The presence of dot-like (parenthesis-like) structure in round or cup-shaped cysts is confirmative and useful for cytological diagnosis.
     
   
     
Reference case 84A
Pneumocystis carinii in bronchial lavage from an AIDS patient (immunostaining using a monoclonal antibody). The clustered cysts are immunoreactive for P. carinii antigen. This microbe is now categorized into the fungal genus.