Signalment:  

9 year-old intact male beagle dog (Canis familiaris) This dog was submitted by a Humane Society that had received several complaints from residents that the dog was neglected and left outdoors during the winter. The dog was found dead and frozen in an outdoor enclosure.

Gross Description:  

The dog was thin (body condition score = 2/5) with easily palpable ribs and only a small amount of subcutaneous fat. There were small amounts of visceral fat and no evidence of serous fat atrophy in the bone marrow. The lungs had dark red mottling with lobes on the right side appearing darker than those on the left.  Additionally, there were multifocal to coalescing tan-white areas (~10% of overall lung volume) that were more firm than the surrounding lung tissue and were slightly collapsed. These areas were mainly distributed along the margins of the lung with the largest area (2 cm X 2 cm) having a dark red center. The stomach was filled with food and had a roughly 2 X 3 cm area of congestion on the serosal and mucosal surfaces. The liver was dark reddish- brown and the gall bladder was mildly distended with bile. Two, roughly 0.5 cm diameter, raised, dark red nodules were noticed on opposite poles of the spleen (consistent with nodular hyperplasia). The kidneys appeared bilaterally dark red. 

Histopathologic Description:

Lung: The firm areas in the lungs correspond histologically to regions with diffuse alveolar fibrosis and infiltration of small to moderate numbers of predominately lymphocytes and plasma cells.  Additionally, almost all of the alveolar spaces and many of the airways in this region are filled with aggregates of amorphous, relatively homogeneous (hyalinized) amphophilic material forming laminated bodies. These bodies are often surrounded by macrophages and occasional multinucleated giant cells. The material is uniformly PAS- positive (Fig 1) and portions of the material, particularly at the margins, are birefringent under polarized light (Fig 2). The surrounding lung parenchyma is often mildly atelectatic and often markedly congested. In regions further away from the affected areas there is mild patchy congestion of the alveolar interstitium and infiltrates of small to moderate numbers of predominately macrophages within alveolar spaces. 

Morphologic Diagnosis:  

Lung: Pneumonia, interstitial, lymphoplasmacytic, histiocytic and fibrosing, multifocal, chronic, severe with intra-alveolar hyaline material (pulmonary hyalinosis). 

Lab Results:  

Scant growth of mixed flora including Bacillus sp. was found on lung tissue culture. 

Condition:  

Pulmonary hyalinosis

Contributor Comment:  

The lung lesions are characteristic of a condition known as pulmonary hyalinosis of dogs (1, 2, 3). Pulmonary hyalinosis is a type of alveolar filling disorder, which is characterized by accumulations of abnormal material in airways. Other disorders in this group include endogenous lipid pneumonia, alveolar proteinosis and alveolar phospholipidosis and alveolar microlithiasis (1). 

The cause of pulmonary hyalinosis is unknown. Some pathologists consider it an incidental finding in older dogs (3), while others postulate that it is a response to inhalation of dust or pneumotoxicants such as silica in uranium ore dust (1) or to non-specific aspirated material (2). This dog did not have any evidence of aspiration and it is unknown whether the unusual material in the lung was also present in the enclosure or environmental surroundings. 

Unfortunately, the definitive cause of death in this dog remained inconclusive. The most significant findings were changes found in the lungs and kidneys and the overall poor body condition. The pulmonary lesions involved only a relatively small portion of the overall volume of lung (about 10%), however where the lesions were present, the normal architecture was completely obliterated. Additionally a moderate, chronic, multifocal-segmental, membranoproliferative glomerulonephritis was detected microscopically. Although no biochemical testing of renal function and urinalysis were done in this dog, there was no evidence of uremic lesions at necropsy, which could have indicated uremia or renal failure. However, as glomerular disease can cause protein loss, this lesion could have potentially contributed to the poor body condition of this dog. 

Although the dog was thin at the time of death, it was not emaciated, as visceral and marrow fat stores were still present, and there was no histologic evidence of hepatocyte or pancreatic atrophy. Abundant food stuffs were present in the stomach, however the long-term food consumption and therefore energy intake of this dog was unknown. Increased food energy is required in animals living in a cold environment to maintain adequate body temperature, so inadequate food intake would also have to be considered as a possible contributing factor to this dog being very thin. 

JPC Diagnosis:  

Lung: Pneumonia, interstitial, granulomatous, chronic, focally extensive, severe, with abundant intra-alveolar hyaline material. 

Conference Comment:  

This unusual canine condition was originally considered a result of aspiration pneumonia and analogous to a condition in humans know as pulmonary nodular granulomatosis, which was often found in nursing home patients with impaired swallowing abilities who were fed soft, legume-based diets. Hyaline rings were experimentally produced in animal lungs by injecting broth of lentils. (4) Lentils consist of grains of starch within honeycomb-like cotyledons; the cotyledons, which are composed of cellulose, incited the hyaline rings. The resulting lesion was termed -�-�-�-�lentil pulse pneumonia. 

In 1972, Dr. Leonard Billups of the Armed Forces Institute of Pathology reported that the canine condition now known as pulmonary hyalinosis was not composed of plant material as in pulse pneumonias; the hyaline bodies in dogs ( known colloquially as Billups bodies) did not stain with silver impregnation stains as leguminous cotyledons do (2). 

Pulmonary hyalinosis may be differentiated from other conditions based upon histologic and staining features. The hyaline bodies are intracellular in macrophages and multinucleated giant cells, occasionally calcify, are birefringent, positive for periodic acid-Schiff (PAS), crystal violet and oil red 0, and ultrastructurally consist of a whorled arrangement of lamellar membranes suggestive of degenerate cells (1,5). Corpora amylacea are rounded, basophilic hyaline masses that are often concentrically laminated. Corpora amylacea are not birefringent, do not calcify, and are weakly PAS positive. Pulmonary microliths are often distributed throughout the lung, and the calcospherites that compose this lesion are concentrically laminated, have radial striations, are calcified, and are intensely positive with PAS and colloidal iron stains, and unlike pulmonary hyalinosis, the material is extracellular (6). 

References:

1. Dagle GE, Filipy RE, Adee RR, Stuart BO. Pulmonary Hyalinosis in Dogs. Vet Pathol 1976; 13: 138-42. 
2. Billups LH, Liu SK, Kelley DF, Garner FM. Pulmonary Granulomas Associated with PAS-Positive Bodies in Brachycephalic Dogs. Vet Pathol 1972; 9: 294-300. 
3. Caswell JL, Williams KJ. Respiratory system. In: Maxie MG, ed. Jubb, Kennedy and Palmers Pathology of Domestic Animals. Vol. 2, 5th ed. Philadelphia, PA: Elsevier-Saunders; 2007: 572-573. 
4. Knoblich R. Pulmonary granulomatosis caused by vegetable particles: socalled lentil pulse pneumonia. Am Rev Respir Dis. 1969;99:380389. 
5. Harrison JD, Martin IC. Oral vegetable granuloma: ultrastructural and histological study. J Oral Pathol. 1986;15:322326. 
6. Rhee DD, Wu ML. Pulse Granulomas Detected in Gallbladder, Fallopian Tube, and Skin. Arch Pathol Lab Med. 2006;130:18391842. 

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