JPC SYSTEMIC PATHOLOGY

RESPIRATORY SYSTEM

September 2017

P-F07

 

Signalment (JPC #2018004):  Unknown age, female Sprague‑Dawley rat

HISTORY:  This Sprague‑Dawley rat was sacrificed at the termination of a steroid dose‑range‑finding study.  This animal was in the high‑dose group fed a diet providing approximately 20 mg steroid/kg BW/day for 13 weeks.

HISTOPATHOLOGIC DESCRIPTION:  Lung:  Affecting 80% of the section, alveolar lumina are expanded by eosinophilic foamy to granular material admixed with low numbers of degenerative neutrophils, macrophages, sloughed epithelial cells and fewer lymphocytes and plasma cells. These inflammatory cells also mildly expand the alveolar septa. Within the eosinophilic exudate and rarely within macrophages are numerous vague, ill-defined, 4-8 um, pale staining round to oval fungal cysts.  Multifocally alveoli are lined by plump cuboidal epithelium (type II pneumocyte hyperplasia).  Multifocally there are perivascular and peribronchiolar aggregates of moderate numbers of plasma cells, fewer lymphocytes and macrophages with mildly ectatic lymphatics. Multifocally, the pleura is lined by enlarged mesothelium (hypertrophy).     

Slide B:  Lung (GMS):  There are numerous 3-4 um round to oval fungal cysts within alveoli and macrophages that stain black with central pallor.

MORPHOLOGIC DIAGNOSIS:  Lung:  Interstitial pneumonia, neutrophilic and histiocytic, diffuse, mild, with type II pneumocyte hyperplasia and foamy alveolar exudate with numerous intraalveolar and intrahistiocytic fungal cysts, etiology consistent with Pneumocystis carinii, Sprague‑Dawley rat, rodent

ETIOLOGIC DIAGNOSIS:  Pulmonary pneumocystosis

CAUSE:  Pneumocystis carinii

GENERAL DISCUSSION:

PATHOGENESIS:

TYPICAL CLINICAL FINDINGS:

TYPICAL GROSS FINDINGS:

TYPICAL LIGHT MICROSCOPIC FINDINGS:

ULTRASTRUCTURE FINDINGS:

ADDITIONAL DIAGNOSTIC TESTS:

DIFFERENTIAL DIAGNOSIS:

COMPARATIVE PATHOLOGY:

REFERENCES:

  1. Barthold SW, Griffey SM, Percy DH, eds. Pathology of Laboratory Rodents & Rabbits, 4th ed. Ames, IA: Blackwell Publishing Ltd; 2016:146-147.
  2. Cailliez JC, Seguy N, Denis CM, Aliouat EM, Mazars E, Polonelli L. Pneumocystis carinii: An atypical fungal micro-organism. J Med Vet Mycol 1996:34:227-239.
  3. Caswell JL, Williams KJ. Respiratory system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. Philadelphia, PA: Elsevier; 2015:535-536.
  4. Henderson KS, Dole V, Parker NJ, Momtsios P, Banu L, Brouillette R, Simon MA, Albers TM, Pritchett-Corning KR, Clifford CB, Shek WR. Pneumocystis carinii causes a distinctive interstitial pneumonia in immunocompetent laboratory rats that had been attributed to "rat respiratory virus".  Vet Pathol. 2012;49(3):440-52.
  5. Jensen TK, Boye M, Bille-Hansen V. Application of fluorescent in situ hybridization for specific diagnosis of Pneumocystis carinii pneumonia in foals and pigs. Vet Pathol 2001;38:269-274.
  6. Jones TC, Hunt RD, King NW. In: Veterinary Pathology. 6th ed. Baltimore, MD: Williams & Wilkins;1997:581-582.
  7. Livingston RS, Besch-Williford CL, Myles MH, Franklin CL, Crim MJ, Riley LK. Pneumocystis carinii infection causes lung lesions historically attributed to rat respiratory virus. Comp Med. 2011;61(1):45-53.
  8. Lopez A, Martinson SA. Respiratory system, mediastinum, and pleurae, In: Zachary JF, ed. Pathologic Basis of Veterinary Disease. 6th ed. St. Louis, MO: Elsevier; 2016:485, 528, 541, 548.


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