Cutaneous asthenia (Ehlers-Danlos-like syndrome) of Burmese cats

Identification of an ADAMTS2 frameshift variant in a cat family with Ehlers-Danlos syndrome

We investigated 4 European domestic shorthair kittens with skin lesions consistent with the dermatosparaxis type of the Ehlers-Danlos syndrome, a connective tissue disorder. The kittens were sired by the same tomcat but were born by 3 different mothers. The kittens had easily torn skin resulting in nonhealing skin wounds. Both clinically and histologically, the skin showed thin epidermis in addition to inflammatory changes. Changes in collagen fibers were visible in electron micrographs. The complete genome of an affected kitten was sequenced. A one base pair duplication leading to a frameshift in the candidate gene ADAMTS2 was identified, p.(Ser235fs*3). All 4 affected cats carried the frameshift duplication in a homozygous state. Genotypes at this variant showed perfect cosegregation with the autosomal recessive Ehlers-Danlos syndrome phenotype in the available family. The mutant allele did not occur in 48 unrelated control cats. ADAMTS2 loss-of-function variants cause autosomal recessive forms of Ehlers-Danlos syndrome in humans, mice, dogs, cattle, and sheep. The available evidence from our investigation together with the functional knowledge on ADAMTS2 in other species allows to classify the identified ADAMTS2 variant as pathogenic and most likely causative variant for the observed Ehlers-Danlos syndrome.

Independent COL5A1 Variants in Cats with Ehlers-Danlos Syndrome

We investigated four cats with similar clinical skin-related signs strongly suggestive of Ehlers-Danlos syndrome (EDS). Cases no. 1 and 4 were unrelated and the remaining two cases, no. 2 and 3, were reportedly siblings. Histopathological changes were characterized by severely altered dermal collagen fibers. Transmission electron microscopy in one case demonstrated abnormalities in the collagen fibril organization and structure. The genomes of the two unrelated affected cats and one of the affected siblings were sequenced and individually compared to 54 feline control genomes. We searched for private protein changing variants in known human EDS candidate genes and identified three independent heterozygous COL5A1 variants. COL5A1 is a well-characterized candidate gene for classical EDS. It encodes the proα1 chain of type V collagen, which is needed for correct collagen fibril formation and the integrity of the skin. The identified variants in COL5A1 are c.112_118+15del or r.spl?, c.3514A>T or p.(Lys1172*), and c.3066del or p.(Gly1023Valfs*50) for cases no. 1, 2&3, and 4, respectively. They presumably all lead to nonsense-mediated mRNA decay, which results in haploinsufficiency of COL5A1 and causes the alterations of the connective tissue. The whole genome sequencing approach used in this study enables a refinement of the diagnosis for the affected cats as classical EDS. It further illustrates the potential of such experiments as a precision medicine approach in animals with inherited diseases.

Animal Models of Ehlers-Danlos Syndromes: Phenotype, Pathogenesis, and Translational Potential

The Ehlers-Danlos syndromes (EDS) are a group of heritable connective tissues disorders mainly characterized by skin hyperextensibility, joint hypermobility and generalized tissue fragility. Currently, 14 EDS subtypes each with particular phenotypic features are recognized and are caused by genetic defects in 20 different genes. All of these genes are involved in the biosynthesis and/or fibrillogenesis of collagens at some level. Although great progress has been made in elucidating the molecular basis of different EDS subtypes, the pathogenic mechanisms underlying the observed phenotypes remain poorly understood, and consequentially, adequate treatment and management options for these conditions remain scarce. To date, several animal models, mainly mice and zebrafish, have been described with defects in 14 of the 20 hitherto known EDS-associated genes. These models have been instrumental in discerning the functions and roles of the corresponding proteins during development, maturation and repair and in portraying their roles during collagen biosynthesis and/or fibrillogenesis, for some even before their contribution to an EDS phenotype was elucidated. Additionally, extensive phenotypical characterization of these models has shown that they largely phenocopy their human counterparts, with recapitulation of several clinical hallmarks of the corresponding EDS subtype, including dermatological, cardiovascular, musculoskeletal and ocular features, as well as biomechanical and ultrastructural similarities in tissues. In this narrative review, we provide a comprehensive overview of animal models manifesting phenotypes that mimic EDS with a focus on engineered mouse and zebrafish models, and their relevance in past and future EDS research. Additionally, we briefly discuss domestic animals with naturally occurring EDS phenotypes. Collectively, these animal models have only started to reveal glimpses into the pathophysiological aspects associated with EDS and will undoubtably continue to play critical roles in EDS research due to their tremendous potential for pinpointing (common) signaling pathways, unveiling possible therapeutic targets and providing opportunities for preclinical therapeutic interventions.

Supernumerary maxillary fourth premolar teeth in five related Burmese cats

Case series summary

This article reports a case series of five Burmese cats with supernumerary teeth. All included cases displayed either unilateral or bilateral supernumerary maxillary fourth premolar teeth. Two cases also displayed supernumerary mandibular fourth premolar teeth, and in one case bilateral supernumerary maxillary third incisor teeth were found. Examination of the pedigrees of the affected cats revealed that all five cats were related with one common ancestor. All patients in this case series were successfully treated.

Relevance and novel information

Supernumerary maxillary fourth premolar teeth in cats have not been reported previously in the literature. As all five cats in this case series were shown to be related, supernumerary maxillary fourth premolar teeth may be yet another heritable health condition affecting the Burmese breed. Therefore, Burmese breeders should endeavour to reduce the incidence of supernumerary teeth within the breed by having animals examined by a veterinary dentist prior to breeding, and neutering affected, as well as related, individuals. Burmese cat owners must be made aware of the condition in order to institute early evaluation, diagnosis and treatment.

A frameshift variant in the COL5A1 gene in a cat with Ehlers-Danlos syndrome

Ehlers-Danlos syndrome (EDS) is a group of heritable connective tissue disorders caused by defective collagen synthesis or incorrect assembly of the collagen triple helical structure. EDS is characterised by joint hypermobility, skin hyperextensibility, abnormal scarring, poor wound healing and tissue friability. Human EDS may be caused by variants in several different genes including COL5A1, which encodes the collagen type V alpha 1 chain. For the present study we investigated a 1.5-year-old, spayed female, domestic shorthair cat with EDS. The affected cat showed multiple recurrent skin tears, hyperextensibility of the skin and joint abnormalities. We obtained whole genome sequencing data from the affected cat and searched for variants in candidate genes known to cause EDS. We detected a heterozygous single base-pair deletion in exon 43 of the COL5A1 gene, namely c.3420delG. The deletion was predicted to result in a frameshift and premature stop codon: p.(Leu1141SerfsTer134). Sanger sequencing confirmed that the variant was present in the affected cat and absent from 103 unaffected cats from different breeds. The variant was also absent from a Burmese cat with EDS. Based on knowledge about the functional impact of COL5A1 variants in other species, COL5A1:c.3420delG represents a compelling candidate causative variant for the observed EDS in the affected cat.

Recanalisation of a congenital extrahepatic portosystemic shunt previously attenuated with cellophane banding in a cat

Case summary

A congenital extrahepatic portosystemic shunt was attenuated with commercial roll cellophane banding in a cat and postoperative liver changes were monitored using CT angiography (CTA). The patient clinically improved after cellophane banding, characterised by resolution of hepatic encephalopathy, weight gain, reference interval (RI) bile acid stimulation tests, as well as CTA-documented increased liver size, increased hepatic vasculature and shunt attenuation. Six months later the cat re-presented with recurrence of clinical signs and increased bile acids. CTA confirmed recanalisation of the shunt. Shunt attenuation was repeated using pure cellophane banding and nearly complete closure of the shunt was later documented by CTA. Seven months later, recanalisation was again documented via CTA and associated with clinical signs and increased bile acids. Complete ligation of the shunt was achieved using a polypropylene ligature and a titanium ligating clip. At long-term follow-up, the cat was clinically well, and bile acids and biochemistry were within the RIs.

Relevance and novel information

This is the first report of CTA-documented recanalisation of an extrahepatic portosystemic shunt previously attenuated with cellophane banding. Recanalisation should be considered as a differential for recurrence of hepatic encephalopathy following cellophane banding.

Skin as a marker of general feline health: Cutaneous manifestations of systemic disease

Practical relevance: Although most skin lesions occur due to diseases primarily affecting the skin, some reflect important systemic diseases. Such lesions may relate directly to the systemic disease, or may occur due to secondary skin diseases that develop because of immunosuppression. Early recognition of skin changes as a marker of systemic disease will maximise patient outcomes. Clinical challenges: In older or clearly debilitated cats presenting with skin disease, the potential for underlying systemic disease is often readily apparent. Similarly, cats presenting with severe ulcerative or multifocal nodular skin lesions, or with concurrent signs of systemic illness, will more instinctively prompt systemic evaluation. More challenging is the cat presenting with alopecic, scaling, erythemic and/or mildly crusted skin disease, with or without pruritus; hypersensitivities and infectious dermatoses are the most common considerations, but occasionally systemic disease underlies the skin changes. Knowing when screening laboratory testing, body imaging or other systemic diagnostics are indicated is not always straightforward. Evidence base: This article reviews cutaneous presentations of systemic diseases reported in the veterinary literature, and discusses important differential diagnoses. The author draws on clinical experience, published data on disease prevalence and case evaluations, and expert opinions on approach to common systemic problems to provide guidance on when investigation for underlying systemic disease is most appropriate.

Surgical and medical treatment of ocular disease in a dog with Ehlers-Danlos syndrome

Correctional surgery was performed on a 3‐year‐old intact male shih tzu presenting with Ehlers–Danlos syndrome, ocular disease, and skin fold dermatitis. A one‐year follow‐up showed that no further clinical corrections were needed. Therefore, surgery could be considered in some canine patients with Ehlers–Danlos syndrome.