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Case of the Month: Cutaneous and renal glomerular vasculopathy (CRGV)

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Erika Abbondati

Board Certified Anatomic Pathologist

Luna, a 6-year-old cross breed female entire dog

Clinical history

A typical clinical history for a CRGV case includes development of one or multiple areas of skin ulceration, often on the abdomen and limbs, followed by lethargy, anorexia, renal injury and loss of function. Samples from the skin and kidney are often submitted post-mortem.

Histology

Histologically the epidermis presents with areas of ulceration and necrosis. Fibrinoid degeneration and vasculitis of the dermal and subcutaneous vessel are often observed. Thrombi formation is also a frequent finding.

Figure 1: Epidermal ulceration and necrosis (green arrow) with overlying serocellular crust (black arrow) with fibrinoid vasculitis of dermal vessels (black circles).

Within the sections of the kidney there is usually extensive glomerular damage. Glomeruli often are hypereosinophilic with loss of cellular details and thickening and distortion of capillary loops and basement membrane with peripheral adhesion to the Bowman’s capsule. Glomerular sclerosis can be observed. Tubules are multifocally lined by degenerate epithelial cells and protein casts are multifocally observed within the lumen. Fibrinoid degeneration of blood vessels is also observed.

Figure 2: Hypereosinophilic glomeruli with diffusely thickened basement membranes and adhesions to the Bowman’s capsule (black circle) and sclerotic glomeruli (more advanced granular degeneration) (green circle).

Figure 3: Sclerotic glomeruli (green circle), tubule lined by degenerate epithelium (green arrow) and tubules containing protein material within the lumen (black arrow).

Cutaneous and renal glomerular vasculopathy (CRGV) is a rare condition that affects dogs only, causing skin lesions and severe kidney damage. This disease is also known as “Alabama Rot,” and it was first identified in Greyhounds in the United States in the 1980s but has since been reported in various breeds, but Hounds, gundogs and pastoral dogs are often overrepresented. CRGV is recognised mainly in the UK, however, a few isolated cases have been reported in Germany and the Republic of Ireland. This disease is characterised by seasonal outbreaks with most cases reported between the months of November and May. Woodland habitat, increased winter temperatures, as well as high rain falls, have been recognised as important factors in the distribution of this disease. Some dogs with CRGV are reported to have been in touch with another dog with it and often multiple dogs in the same household can be affected.

Despite extensive research, the exact cause of CRGV remains elusive and the condition often presents a diagnostic and therapeutic challenge for veterinarians in the UK.

CRGV typically begins with skin lesions, particularly on the limbs, abdomen, and muzzle and these patients are often lame. Skin lesions usually consist of ulcers or erosions, accompanied by oedema, and pain. Affected dogs may also exhibit signs of systemic illness, such as lethargy, anorexia, vomiting, and fever. As the disease progresses, renal injury and eventually renal failure occur.

The pathogenesis of CRGV is not fully understood, but it involves damage to small blood vessels, particularly the glomerular capillaries in the kidneys, leading to endothelial damage, fibrin deposition, thrombi formation, ischemia and organ damage with subsequent loss of function. Currently there is no single reliable test for an ante-mortem diagnosis of CRGV in dogs and histopathology examination of the kidney remains the gold standard for identification of the thrombotic microangiopathy, which is considered the histopathological hallmark of this disease. For this reason, samples are often submitted post-mortem for confirmation of a clinical suspicion.

Ingestion of bacteria-associated Shiga toxins has been proposed as a possible underlying cause, however, studies have failed to consistently identify the presence of toxins, bacteria, viruses or other microorganisms in the affected tissues.

Diagnosis of CRGV relies on a combination of typical clinical signs, biochemical tests, and histopathological evaluation. Skin biopsies can be helpful and reveal changes consistent with vasculopathy, which may help the clinician identify this disease.

References:

Walker JJA, Holm LP, Sarmiento ÓG, Caianiello R, Cortellini S, Walker DJ. Clinicopathological features of cutaneous and renal glomerular vasculopathy in 178 dogs. Vet Rec. 2021 Aug;189(4):e72. doi: 10.1002/vetr.72. Epub 2021 Jan 24. PMID: 33829498.

Holm LP, Stevens KB, Walker DJ. Pathology and Epidemiology of Cutaneous and Renal Glomerular Vasculopathy in Dogs. J Comp Pathol. 2020 Apr;176:156-161. doi: 10.1016/j.jcpa.2020.03.003. Epub 2020 Apr 8. PMID: 32359630.

Hope A, Martinez C, Cassidy JP, Gallagher B, Mooney CT. Canine cutaneous and renal glomerular vasculopathy in the Republic of Ireland: a description of three cases. Ir Vet J. 2019 Nov 16;72:13. doi: 10.1186/s13620-019-0151-7. PMID: 31762988; PMCID: PMC6858974.