Case 171020 -3

10-year-old, female spayed, English bulldog

The patient presented to the UC Davis Community Practice for a one month history of lethargy and hyporexia after initially presenting to the rDVM. Bloodwork performed at the rDVM showed a mixed hepatopathy and mild thrombocytopenia. Bloodwork performed at UCD demonstrated a prolonged PT/PTT, elevated D-dimer, low fibrinogen, hypoalbuminemia, hyperbilirubinemia, azotemia, stress leukogram, and a moderate normochromic, normocytic, nonregenerative anemia. Additionally, the patient was hypothermic and was noted to have pleural effusion and lymphadenomegaly. Due to concern for poor prognosis and financial constraints, the owners elected euthanasia.

Diffusely, the patient’s mucosal membranes, ventral abdomen, and internal fat stores (subcutaneous, perirenal, omental) are light yellow. The omental fat is adhered to the right lateral body wall. Approximately 10 mL of light red, translucent fluid is noted in the abdomen. The liver is diffusely mottled light to dark brown with multifocal to coalescing regions of soft, light tan hepatic parenchyma with dark brown, cavitated centers present affecting approximately 50% of all liver lobes.

N/A

Liver: Three sections of liver are examined in which approximately 85% of the hepatic parenchyma is necrotic and infiltrated by large numbers of histiocytes with fewer lymphocytes, plasma cells, and neutrophils, along with fibroblasts. Necrosis is characterized by loss of cellular detail and individualization of hepatocytes with pyknotic to karyorrhectic nuclei. Multifocal aggregates of extravastated erythrocytes (hemorrhage) are scattered throughout the necrotic regions. In less affected regions, the inflammatory population appears to surround vessels. Centrilobular Kuppfer cells contain dark brown granular pigment. There is lobular collapse in the less affected regions, with a minimally undulating hepatic capsule, and hepatocytes are occasionally binucleate.

CD18: Histiocytes demonstrate strong immunoreactivity, highlighting the angiocentric nature of the lesion.

Systemic reactive hepatic histiocytosis with acute, submassive hepatic necrosis

Immunohistochemistry was used to confirm the identify of cells within the liver as being of histiocytic origin. Reactive histiocytes were noted within the liver, lymph node, and spleen. Submassive necrosis within the liver, splenic necrosis, bicavitary effusion, and icterus are considered secondary to reactive histiocytosis. Systemic reactive histiocytosis is a proliferative disease thought to arise through dysfunction of the immune system and be antigen driven. Lesions are pleocellular but dominated by histiocytes and lymphocytes. Histiocytes are relatively normal in appearance, which helps to differentiate reactive histiocytosis from histiocytic sarcoma. Lesions tend to be centered n the vasculature. Histiocytes of reactive histiocytosis (and cutaneous histiocytes) are of dendritic cell origin and generally express CD1a, CD11c/CD18, MHC class II, CD4, and CD90/thy-1. They should be E-cadherin negative.

Moore, Peter.Systemic Reactive Histiocytosis. Canine and Feline Histiocytosis, UC Davis, www.histiocytosis.ucdavis.edu/k9_histio.html#SH.