5 year old, ovariohyster-ectomized female Cavalier King Charles spaniel, Canis familiaris.An adult spayed female Cavalier King Charles Spaniel reported to be 5 years old from a the household with multiple dogs exhibiting increased respiratory rate and cough. During thoracic radiographs the patient became agonal and arrested despite attempted cardiopulmonary resuscitation. Radiographs revealed pneumonia. The patient was presented for necropsy 1.5 hours following death.

Gross Description:  

The trachea is diffusely mildly compressed dorsoventrally. Excluding a limited regional portion of the cranial aspect of the left cranial lung lobe, the lungs are diffusely dark red, heavy, and sink in formalin. The heart is mildly enlarged with mild nodular thickening of the mitral valve. A small portion of the cerebellar vermis protrudes through a mildly narrowed and irregular foramen magnum.

Histopathologic Description:

Lung: Alveoli and bronchioles frequently are filled with macrophages, neutrophils, cellular debris, erythrocytes, multinucleate giant cells and edema.  The macrophages are frequently vesciulate, occasionally containing cellular and karyorrhectic debris. Random, individual to multiple, golden-brown, 3-5Μm diameter fungal spores are present both within macrophages and free within the alveolar lumens. Alveolar septa are occasionally lined by finely fibrillar to glassy eosinophilic material (hyalin mem-branes). Alveolar epithelial cells are multifocally cuboidal (type II pneumocyte hyperplasia) with rare binucleate and multinucleate cells. There is multifocal loss of the bronchiolar epithelium, with in-frequent epithelial dysplasia.  A few peri-bronchiolar macrophages contain black granular pigment (anthracosis). Moderate numbers of plasma cells with fewer lymp-hocytes surround pulmonary vessels. Vascular endothelial cells are frequently hypertrophic. Pleural mesothelial cells are hypertrophic.

Morphologic Diagnosis:  

Marked, diffuse, histiocytic interstitial pneumonia with fungal spores.

Lab Results:  

Sample: Lung
Test: Aerobic Culture
Result: No growth seen in 3 days

PCR/DNA sequencing
99 % nucleotide identity with Lycoperdon pyriforme (AY854075.1, strain AFTOL-ID48) over 682 bp.


Lycoperdon spp. fungal pneumonia

Contributor Comment:  

The intrahistiocytic and free fungal spores within the lung were identified as spores of “puffball” mushrooms by PCR and DNA sequencing. Eleven species of puffball mushrooms (Lycoperdon sp.) are indigenous to the area from which this case originated (greater Smoky Mountains). Inhalation of spores has been reported infrequently in association with pneumonia (pulmonary lyco-perdonosis) in dogs1,8 and humans7,9.

JPC Diagnosis:  

 Lung: Pneumonia, interstitial, necrotizing, fibrinosuppurative, and histiocytic, diffuse, chronic, severe with hyaline membrane formation and rare intra-histiocytic fungal spores.

Conference Comment:  

Pulmonary lesions caused by the inhalation of Lycoperdon sp. spores are theorized to result from the host hypersensitivity response to fungal spores acting as foreign bodies rather than an infectious process.2,7 The failure to culture Lycoperdon from a reported case and inability of this saprophytic fungus to germinate under normal physiologic body temperatures supports this theory.7 Hyp-ersensitivity pneumonitis (HP), also known as extrinsic allergic alveolitis, is caused by intense and often prolonged exposure to inhaled organic antigens such as fungal spores, but can also include bacterial products and animal proteins. This disease is commonly diagnosed in dairy cows and horses housed indoors and usually affect multiple animals within a group. It results from chronic inhalation of spores of thermophilic actinomycetes (Saccharo-physpora rectivirgula) found in moldy hay.5,6 This is followed by an antibody response to inhaled antigen and local deposition of antigen-antibody complexes (Arthus reaction) as well as the formation of multifocal granulomas suggesting a T-cell-mediated response. This type of reaction suggests both type III and type IV hypersensitivity response 2,5,7 (See WSC 2012-2013, conference 22, case 4 for a review of hypersensitivity reactions).

Characteristic lesions in animal and human HP include proliferation of type II pneumocytes and fibrosis of alveolar septa and peribronchiolar tissue. In severe cases, hyaline membranes composed of fibrin, serum proteins, and cell debris line the alveolar septa.5 This hyaline membrane causes alveolar occlusion resulting in severe hypoxia and death.

Conference participants noted the severe necrotizing and inflammatory changes to the lung interstitium, but had difficult time finding the rare fungal spores present in the tissue. Interestingly, clinical disease of lycoperdonosis in humans and dogs only occurs following a massive inhalation dose of puffball conidia7; however in this section there is a paucity of spores present. As a result, there was discussion of differentials for hyaline membrane formation, which is the most striking histologic feature in this case. Acute respiratory distress syndrome (ARDS) in the dog was discussed as having a similar histopathologic appearance to this case. In addition to hyaline membranes, type II pneumocyte hyperplasia, and bronchiolar epithelial necrosis is a consistent feature of ARDS. Inciting causes include: trauma, shock, disseminated intravascular coag-ulation, septicemia, smoke inhalation, oxygen toxicity, viral infection, and strangulation among others.4

This case was additionally studied in consultation with the Department of Pulmonary and Mediastinal Pathology at the Joint Pathology Center, who disagreed with the purported mechanisms discussed above, based on the morphologic changes noted in this section. Their interpretation is that this section of lung is diagnostic for diffuse alveolar damage (DAD) due to a toxic reaction to Lycoperdon spores rather than HP, published in a case report from this animal.2 DAD is the most commonly identified form of interstitial lung disease and is the histologic correlate to the clinical condition of ARDS, discussed by conference participants.4 The pulmonary pathologists describe an intra-alveolar inflammatory infiltrate composed predominantly of neutrophils and macrophages. This is admixed with focal plasma cells and lymphocytes, hyaline membranes, and acute inflammation of bronchiolar epithelium, along with multifocal fungal spores. They see no histologic evidence to support the diagnosis of HP. They also note the importance of recognizing this entity as DAD, and not HP, due to the high mortality rate for DAD, even with intensive supportive treatment.


1. Aleghat T, Kellett-Gregory L, Van Winkle T: Lycoperdonosis in a dog, Vet Pathol. 2009;46:1046.

2. Alenghat T, Pillitteri C et al. Lycoperdonosis in two dogs. J Vet Diagn Invest. 2010;22:1002-1005.

3. Buckeridge D, Torrance A, Daly M.  Puffball mushroom toxicosis (lycoperd-onosis) in a two-year-old dachshund. Vet Rec.  2011;168:304.

4. Caswell J, Williams K. Respiratory system. In: Maxie MG, ed.  Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals. Vol 2. 6th ed. Philadelphia, PA: Elsevier Saunders; 2016: 514.

5. Husain AN. The Lung. In: Kumar V, Abbas AK, Aster JC, eds. Pathologic Basis of Disease. 9th ed. Philadelphia, PA: Elsevier Saunders; 2015:694-695.

6. Lopez A. Respiratory system, media-stinum, and pleurae. In: Zachary JF, McGavin MD, eds. Pathologic Basis of Veterinary Disease. 5th ed. St. Louis, MO: Elsevier; 2012:513.

7. Munson E, Panko D, Fink, J.  Lycoperdonosis: Report of Two Cases and Discussion of the Disease: Clin Microbiol Newsl. 1997;19(3):17-20.

8. Rubensohn M: Inhalation pneumonitis in a dog from spores of puffball mushrooms. Can Vet Journal. 2009;50(1):93.

9. Taft T, Cardillo R et al. Respiratory illness associated with inhalation of mushroom spores-Wisconsin, 1994. MMWR Morb Mortal Wkly Rep. 1994;43(29):525-526.

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4-1. Lung.

4-2. Lung, dog.

4-3. Lung, dog.

4-4. Lung.

4-5. Lung.

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