A 2-year-old mixed-breed dog presented with a several-week history of diarrhea.
History & Examiniation
The dog had shown no signs of improvement after empiric deworming. In addition to diarrhea, the dog had started vomiting the week before presentation. Examination revealed a body condition score of 3/9, elevated body temperature of 103.9°F (normal, 100.5°F–102.5°F), and generalized lymphadenopathy.
Diagnostics
Abdominal ultrasonography revealed hepatomegaly and splenomegaly with peritoneal effusion. CBC and serum biochemistry findings indicated mild normocytic, normochromic anemia with moderate leukocytosis (mature neutrophilia) and hypoproteinemia, along with decreased albumin and globulin levels (Table).In addition, fine-needle aspiration and cytology of the right prescapular lymph node were performed.
Ask Yourself
Based on the stained cytology sample shown above:
- Is a mixed lymphoid population present, predominated by small lymphocytes?
- Are any inflammatory cells identified?
- Are other nonlymphoid cells observed?
Diagnosis: Pyogranulomatous lymphadenitis with Histoplasma capsulatum
H. capsulatum, a dimorphic fungal organism, can be readily diagnosed by cytology.1,2 In dogs, weight loss, fever, and inappetence are common clinical findings. Laboratory findings are often nonspecific and can vary, depending on the extent of organism dissemination. H. capsulatum has been identified in the peripheral blood and bone marrow.3 In this case, the patient had disseminated disease and organisms were identified in the spleen, liver, peritoneal fluid, and all peripheral lymph nodes.
Differential Diagnosis
The lymphoid population was mixed and was predominated by small lymphocytes with fewer large and intermediate-size lymphocytes (Figure 1). Many plasma cells were also identified, along with many inflammatory cells, primarily neutrophils and macrophages (Figures 2 and 3). This combination is consistent with pyogranulomatous inflammation.