Solid intraocular xanthogranuloma in three Miniature Schnauzer dogs

Clustering analysis of lipoprotein profiles to identify subtypes of hypertriglyceridemia in Miniature Schnauzers

BACKGROUND

Hypertriglyceridemia (HTG) is prevalent in Miniature Schnauzers, predisposing them to life-threatening diseases. Varied responses to management strategies suggest the possibility of multiple subtypes.

HYPOTHESIS/OBJECTIVE

To identify and characterize HTG subtypes in Miniature Schnauzers through cluster analysis of lipoprotein profiles. We hypothesize that multiple phenotypes of primary HTG exist in this breed.

ANIMALS

Twenty Miniature Schnauzers with normal serum triglyceride concentration (NTG), 25 with primary HTG, and 5 with secondary HTG.

METHODS

Cross-sectional study using archived samples. Lipoprotein profiles, generated using continuous lipoprotein density profiling, were clustered with hierarchical cluster analysis. Clinical data (age, sex, body condition score, and dietary fat content) was compared between clusters.

RESULTS

Six clusters were identified. Dogs with primary HTG were dispersed among 4 clusters. One cluster showed the highest intensities for triglyceride-rich lipoprotein (TRL) and low-density lipoprotein (LDL) fractions and also included 4 dogs with secondary HTG. Two clusters had moderately high TRL fraction intensities and low-to-intermediate LDL intensities. The fourth cluster had high LDL but variable TRL fraction intensities with equal numbers of NTG and mild HTG dogs. The final 2 clusters comprised only NTG dogs with low TRL intensities and low-to-intermediate LDL intensities. The clusters did not appear to be driven by differences in the clinical data.

CONCLUSIONS AND CLINICAL IMPORTANCE

The results of this study support a spectrum of lipoprotein phenotypes within Miniature Schnauzers that cannot be predicted by triglyceride concentration alone. Lipoprotein profiling might be useful to determine if subtypes have different origins, clinical consequences, and response to treatment.

Effect of a low-fat diet on serum triglyceride and cholesterol concentrations and lipoprotein profiles in Miniature Schnauzers with hypertriglyceridemia

Background

Hypertriglyceridemia is common in Miniature Schnauzer (MS). Dietary management of hypertriglyceridemia is important, but no studies are available.

Hypothesis/Objectives

To evaluate the effect of a commercially available low‐fat diet on serum triglyceride and cholesterol concentrations and lipoprotein profiles in MS with hypertriglyceridemia.

Animals

Sixteen MS with hypertriglyceridemia and 28 MS without hypertriglyceridemia.

Methods

Prospective clinical trial. Four blood samples (1‐2 months before and 1 day before diet change and 2 and 3 months after the dogs were fed the low‐fat diet) were collected from the MS with hypertriglyceridemia.

Results

Serum triglyceride concentrations for the 2 samples after the diet change (median of sample 3 = 177 mg/dL; range, 48‐498; median of sample 4 = 168 mg/dL; range, 77‐745) were significantly lower than the 2 samples before the diet change (median of sample 1 = 480 mg/dL; range, 181‐1320; median of sample 2 = 493 mg/dL; range, 114‐1395; P < .001). Serum cholesterol concentrations for the 2 samples after the diet change (mean for sample 3 = 257 mg/dL, SD = 82.2; mean for sample 4 = 178 mg/dL, SD = 87.4) were also significantly lower than the 2 samples before the diet change (mean for sample 1 = 381 mg/dL, SD = 146.1; mean for sample 2 = 380 mg/dL, SD = 134.7; P < .001). Before the diet change, 15/16 (94%) of hyperlipidemic MS were classified as hyperlipidemic based on their lipoprotein profiles alone. After the diet change, significantly fewer MS (7/16; 44%; odds ratio = 19.3; 95% CI = 2.0‐184.0; P = .006) were classified as hyperlipidemic based on lipoprotein profile analysis.

Conclusions and Clinical Importance

The study diet was effective in reducing serum triglyceride and cholesterol concentrations and correcting lipoprotein profiles in MS with hypertriglyceridemia.

Improvement Effect of 5-Aminolevulinic Acid on Hyperlipidemia in Miniature Schnauzer Dogs: An Open Study in 5 Cases of One Pedigree

This is the first study to examine the long-term effect of 5-aminolevulinic acid mainly on serum lipoproteins in dogs with hyperlipidemia. We studied 5 Miniature Schnauzer cases whose fasting serum total triglyceride and very-low-density lipoprotein of triglyceride levels were extremely high (635 ± 116 and 520 ± 92 mg/dL, respectively). Although the total cholesterol values were normal, the very-low-density lipoprotein of cholesterol level was high (49 ± 7 mg/dL). Each dog received a 5-aminolevulinic acid supplement (5 mg/day) orally for 6 months. The mean values of total triglyceride, very-low-density lipoprotein of both triglyceride and cholesterol decreased significantly after the treatment period (319 ± 29, 245 ± 18, and 27 ± 2 mg/dL, respectively, P < 0.05). Our present results may present evidence that 5-ALA administration contributes to improvement of hyperlipidemia in Miniature Schnauzer.

Retrospective review of cataract surgery outcomes in Miniature Schnauzers

OBJECTIVE

Miniature Schnauzers commonly develop both inherited and diabetic cataracts. Miniature Schnauzers also often present with concurrent metabolic disease at the time of cataract surgery. The purpose of this study was to evaluate cataract surgery outcomes in Miniature Schnauzers.

MATERIALS AND METHODS

The Eye Care for Animals electronic medical record database (2012-2018) was searched for "phacoemulsification" and "Miniature Schnauzer." A minimum follow-up time of 1 year was required for inclusion in the study. Clinical history, pre- and postoperative bloodwork, postoperative treatments, and visual outcomes were reviewed in all cases.

RESULTS

Cataract surgery was performed on 67 patients and 124 eyes. 93.5% (116/124) of operated eyes were visual 1 year following cataract surgery. At the time of surgery, 79.1% were diabetic, 64.2% had hypercholesterolemia, 55.2% had hypertriglyceridemia, 16.4% had hyperadrenocorticism, and 9% had a history of pancreatitis. Dorzolamide was used postoperatively in 61.2% of patients, and its use was significantly associated with postoperative cholesterol levels above reference range. Lipemic aqueous occurred in 13.4% of patients.

CONCLUSIONS

Miniature Schnauzers presenting for cataract surgery are frequently affected by metabolic diseases and dyslipidemia; however, cataract surgery outcomes were not significantly affected during the study period. Dietary management, omega-3 fatty acid supplementation, and oral fibrates may reduce the incidence of lipemic aqueous in Miniature Schnauzers.

A retrospective analysis of lipid-laden aqueous humor in dogs: Thirty cases

OBJECTIVE

To describe the clinical presentation and outcome of canine patients that present with lipid-laden aqueous humor (LLA) and to evaluate its association with other ocular and systemic disorders.

METHODS

Medical records were identified and reviewed of 30 dogs presenting with clinical signs of LLA between 2013 and 2017 and compared to the canine referral population during the same time period. The percentage of dogs affected by LLA and potential risk factors were compared between groups.

RESULTS

There were 40 eyes in 30 dogs with LLA out of 8011 (0.4%) referrals. The mean age of dogs with LLA was significantly younger than dogs without LLA (P = .0334). Sex was not associated with LLA. Miniature Schnauzers were more likely to have LLA than mixed breeds (P < .0001). Incidence of LLA was significantly higher in eyes also affected by corneal ulceration (P = .0018) or phacoemulsification (P = .0001). Sixty-two percent and 51% of dogs with LLA had concurrent diabetes mellitus and hypertriglyceridemia, respectively. Average triglyceride level of dogs with LLA was 1087 mg/dL (±544) (reference 50-150 mg/dL) and average cholesterol level was 575 mg/dL (±232) (reference 125-300 mg/dL). Complete resolution of LLA was achieved in all dogs re-examined with an average of 20.2 days (range 4-175 days) after diagnosis. There were 6/30 dogs lost to follow-up. Recurrence of LLA occurred at least once in 4/24 dogs (16.7%) after resolution.

CONCLUSIONS

Lipid-laden aqueous humor occurs more frequently in Miniature Schnauzers. Corneal ulceration and phacoemulsification are risk factors. Complete resolution was seen in all cases with a low incidence of recurrence.

A clinicopathological study of 17 cases of ocular surface xanthogranuloma in dogs

OBJECTIVE

To evaluate the clinical, histopathological, and immunohistochemical features of 17 cases of ocular surface xanthogranuloma (OSX) in dogs.

METHODS

Archived records from the Comparative Ocular Pathology Laboratory of Wisconsin (COPLOW) were searched for cases of canine OSX. Cases were evaluated for lipid-laden macrophages and Touton giant cells. Seventeen cases matching those criteria were identified (1993-2018). Clinical and epidemiological data were collected from the submission forms and additional follow-up survey.

RESULTS

Ocular surface xanthogranuloma in dogs presented as small bland nodules. OSX commonly occurred at the limbus (8/17) or cornea (4/17). Three of 17 affected animals were less than 1-year-old and the average age was 6.9 years (range 0.7-14 years). Fourteen of 17 cases did not report any lipid or metabolic abnormalities. Histologically, lesions were composed mainly of dense sheets of vacuolated lipid-laden macrophages and Touton giant cells with scant additional inflammatory cells and an intact overlying epithelium. No recurrence was noted in cases where complete surgical resection was achieved, and medical treatment either pre or post-resection led to only partial resolution.

CONCLUSIONS

Xanthogranulomas are histiocytic lesions characterized by abundant lipid-laden macrophages. The authors use the term, ocular surface xanthogranuloma, to describe nodules with rigidly defined cellular characteristics. Although these lesions share characteristics with human limbal xanthogranulomas, further investigation is needed to suggest the different subsets that have been reported in the medical literature. Complete surgical excision is the most effective treatment for OSX in dogs, and intralesional triamcinolone and topical steroids can be useful adjunctive therapies to surgery.

Limbal xanthogranuloma in a dog

A 10-year-old female spayed American Pitt Bull Terrier was presented with a slow growing mass on the temporal limbus area of the right eye. Canine nodular granulomatous episclerokeratitis was suspected, and the affected eye was treated with 1% prednisolone acetate ophthalmic suspension and 0.03% Tacrolimus ophthalmic solution. As the lesion did not respond to the medical treatments and continued to grow, the mass was excised by lamellar sclerokeratectomy. Microscopically, the mass was composed of granulomatous inflammation with intrahistiocytic lipids and lakes of acicular cholesterol clefts, histopathology findings consistent with xanthogranuloma. To the authors’ knowledge, this is the first canine report of limbal xanthogranuloma.

Proteinuria and lipoprotein lipase activity in Miniature Schnauzer dogs with and without hypertriglyceridemia

Spontaneous hyperlipidemia in rats causes glomerular disease. Idiopathic hypertriglyceridemia (HTG) is prevalent in Miniature Schnauzers, but its relationship with proteinuria is unknown. Decreased activity of major lipid metabolism enzymes, lipoprotein lipase (LPL) and hepatic lipase (HL), may play a role in the cyclic relationship between hyperlipidemia and proteinuria. These enzymes have also not been previously investigated in Miniature Schnauzers. The aims of this study were to determine the relationship between HTG and proteinuria in Miniature Schnauzers and to measure LPL and HL activities in a subset of dogs. Fifty-seven Miniature Schnauzers were recruited (34 with and 23 without HTG). Fasting serum triglyceride concentrations and urine protein-to-creatinine ratios (UPC) were measured in all dogs, and LPL and HL activities were determined in 17 dogs (8 with and 9 without HTG). There was a strong positive correlation between triglyceride concentration and UPC (r = 0.77-0.83, P < 0.001). Proteinuria (UPC ≥ 0.5) was present in 60% of dogs with HTG and absent from all dogs without HTG (P < 0.001). Proteinuric dogs were not azotemic or hypoalbuminemic. Dogs with HTG had a 65% reduction in LPL activity relative to dogs without HTG (P < 0.001); HL activity did not differ. Proteinuria occurs with HTG in Miniature Schnauzers and could be due to lipid-induced glomerular injury. Reduced LPL activity may contribute to the severity of HTG, but further assay validation is required.

Clinical, morphologic, and immunohistochemical features of canine orbital hibernomas

Hibernomas are uncommon benign tumors of brown fat that occur in humans and various animal species. They have not been observed in the orbit of dogs, humans, or other animals. Here we report clinical, light and electron microscopic, and immunohistochemical features of a series of 7 hibernomas arising in the orbital region of dogs. These neoplasms occurred in adult dogs with no breed predilection. The mean age of the affected dogs was 10.4 years (range, 8-13 years). All neoplasms presented as soft lobular masses composed of predominantly round or polygonal neoplastic cells with granular eosinophilic and vacuolated cytoplasm resembling adipocytes. The cytoplasm contained large numbers of pleomorphic mitochondria with dense matrices and indistinct cristae. Immunohistochemical evaluation confirmed positive labeling of neoplastic cells from all cases with uncoupling protein 1 (UCP-1) consistent with brown fat differentiation. Interestingly, rare neoplastic cells also expressed myogenin and myoD, possibly suggesting a common progenitor cell for neoplastic brown adipose and skeletal muscle cells.

Glaucoma in a New Zealand White Rabbit Fed High-cholesterol Diet

Goniodysgenesis, malformation of the filtration angle, was observed in a New Zealand white rabbit supplied with 100 g/day rabbit chow containing 0.2% cholesterol for 10 months. Histopathology revealed cupping of the optic disc, atrophy of the retina and hyalinization of the ciliary body in the bilateral eyeballs. These findings corresponded with histopathological features caused by glaucoma. On the basis of these findings, we diagnosed this lesion as glaucoma, and classified it as primary glaucoma because of the presence of developmental defects of the filtration angle. In this case, hypercholesterolemia-induced changes, such as aggregation of lipid-laden macrophages and cholesterin clefts in the sclera or choroid, might cause deterioration of the lesions in glaucoma.

Use of a meal challenge test to estimate peak postprandial triglyceride concentrations in dogs

OBJECTIVE

To develop a standardized meal challenge test by assessing associations between food-withheld preprandial (ie, fasting) and postprandial triglyceride concentrations, determining the most appropriate sampling time to detect the peak concentration (highest postprandial concentration), and estimating reference intervals for fasting and postprandial concentrations in healthy dogs.

ANIMALS

12 lean healthy mixed-breed dogs.

PROCEDURES

Dogs were fed a dry commercially available diet (fat, 31% metabolizable energy) for 3 weeks. After food was withheld for 23 to 24 hours, plasma triglyceride concentrations were measured 1 and 0.083 hours before and 1, 2, 3, 4, 5, 6, 9, and 12 hours after feeding of a standardized challenge meal (median amount eaten, 63 kcal/kg [127 kcal/kg⁰.⁷⁵]). Correlation and agreement between concentrations at peak and other time points were assessed by use of correlation coefficients and Bland-Altman limits of agreement. Reference intervals were calculated by use of a robust method.

RESULTS

Fasting and peak triglyceride concentrations were not closely associated. The highest concentration among samples obtained 2, 5, and 6 hours after meal consumption had closest agreement with peak concentration. In 5 of 12 dogs, concentrations 12 hours after eating were still significantly above baseline concentration (mean of each dog's fasting concentrations).

CONCLUSIONS AND CLINICAL RELEVANCE

Fasting triglyceride concentration could not be used to accurately predict peak concentration. When estimating peak concentration, multiple samples should be collected 2, 5, and 6 hours after consumption of a standardized meal. Food may need to be withheld for > 12 hours when assessing fasting concentrations in healthy dogs.

Cerebral xanthomatosis in three green water dragons (Physignathus cocincinus)

Cerebral xanthomatosis was diagnosed in three female green water dragons (Physignathus cocincinus), all of which presented with progressive neurologic signs. No antemortem evidence for xanthomatosis was identified, but on postmortem examination cholesterol granulomas, composed of cholesterol clefts surrounded by macrophages and multinucleated giant cells, were found in the forebrain of each animal and were associated with significant displacement and pressure on the adjacent brain. Although the cause of xanthomatosis in these animals is unknown, nutrition and trauma may be involved in the pathogenesis of this condition. Cerebrum, cholesterol, green water dragon, Physignathus cocincinus, xanthoma.