A challenging case: An unusual cause of blindness in a Siberian husky - Veterinary Medicine
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A challenging case: An unusual cause of blindness in a Siberian husky
Despite a lack of other obvious physical abnormalities or signs, systemic disease was suspected of causing this dog's eye problems.


VETERINARY MEDICINE


ADDITIONAL DIAGNOSTIC TESTS

Blood was drawn for a cbc, a serum chemistry profile, fungal titers (to rule out aspergillosis, blastomycosis, coccidioidomycosis, cryptococcosis, and histoplasmosis), and Leptospira species titers. A fecal sample and urine sample (collected by cystocentesis) were submitted for analysis. The history of neoplastic mass removal along with the previous thoracic radiographic findings suggested a metastatic neoplasm could be contributing to the dog's panuveitis, so abdominal ultrasonographic and thoracic radiographic examinations were performed. In addition, ocular ultrasonography was performed to allow better visualization of the posterior segment of the right eye.

The results of the CBC were normal. The serum chemistry profile revealed mild azotemia (blood urea nitrogen = 35 mg/dl, normal = 7 to 32 mg/dl; creatinine = 2.3 mg/dl, normal = 0.4 to 1.5 mg/dl). The dog was seronegative for all fungal and Leptospira species, and the results of the fecal examination were negative. Urinalysis revealed a low urine specific gravity (1.006), a few red blood cells, and moderate numbers of bacteria (later identified on culture as Serratia marcescens, a relatively common opportunistic pathogen). No other organisms were seen in the urine sediment.


Figure 3
No evidence of metastatic neoplasia nor other abnormalities were identified on the thoracic radiographs, and the abdominal ultrasonographic examination revealed hypoechoic nodules in the spleen and liver and a small heterogeneous mass in the area of the previously removed left adrenal gland. An ultrasound-guided fine-needle aspirate of this mass was obtained after the patient was sedated. Interpretation of the abdominal ultrasonographic examination was that the liver and splenic nodules likely represented metastases from the previously diagnosed hepatic adenocarcinoma and that the mass in the adrenal region was a hematoma or granuloma.


Figure 4
Ocular ultrasonographic examinations showed bilateral retinal detachments (Figures 3 & 4). A pocket of fluid was seen in the nasal and ventral retrobulbar areas of both eyes, and the right globe appeared distorted. A sample of fluid from beneath the detached retina of the right eye was obtained with the aid of ultrasonography and submitted for cytologic evaluation.

DIAGNOSIS AND TREATMENT


Figure 5
Cytologic examination of the subretinal aspirate revealed a high cellularity and a finely granular eosinophilic background. The cellular content consisted of 10-to-20-m, ovoid-to-reniform, pale basophilic organisms (Figure 5). Each had 1-to-2-m, round-to-globular basophilic structures within its cell wall. Rare degenerate neutrophils were phagocytizing the organisms, which were tentatively identified as Prototheca species. Protothecosis was confirmed by culture (on Sabouraud's dextrose agar), and the organism was further identified as Prototheca wickerhamii.

The results of cytologic examination of the fine-needle aspirate from the left adrenal area showed that there were cells that appeared to be adrenal in origin but did not possess criteria of malignancy. In addition, a few oddly appearing cells were identified that were probably Prototheca organisms.

The dog was discharged from the hospital, and the owner was informed that the disease carried a grave prognosis. The owner was given the option of administering antifungal therapy with amphotericin B, with or without itraconazole, but because of the prognosis, specific antiprotozoal therapy was declined. However, the urinary tract infection was treated with enrofloxacin (4 mg/kg orally once daily for 14 days), and palliative therapy for the uveitis (prednisolone acetate 1% solution, one drop four times daily in both eyes) was instituted.


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Source: VETERINARY MEDICINE,
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