Canine noninflammatory alopecia: An approach to its classification and a diagnostic aid.

Noninflammatory alopecia is common in dogs and is a frequent cause to consult a veterinarian. It is also a common reason to take biopsies. Noninflammatory alopecia can be attributed to a decreased formation or cytodifferentiation of the hair follicle or the hair shaft in utero, resulting in congenital alopecia. Congenital alopecia often has a hereditary cause, and examples of such disorders are ectodermal dysplasias associated with gene variants of the ectodysplasin A gene. Noninflammatory alopecia may also be caused by impaired postnatal regeneration of hair follicles or shafts. Such disorders may have a clear breed predilection, and alopecia starts early in life. A hereditary background is suspected in those cases but has not been proven. They are referred to as follicular dysplasia although some of these disorders present histologically like a hair cycle disturbance. Late-onset alopecia is usually acquired and may be associated with endocrinopathies. Other possible causes are impaired vascular perfusion or stress. As the hair follicle has limited possible responses to altered regulation, and histopathology may change during the course of a disease, a detailed clinical history, thorough clinical examination including blood work, appropriate biopsy site selection, and detailed histological findings need to be combined to achieve a final diagnosis. This review aims to provide an overview about the known noninflammatory alopecic disorders in dogs. As the pathogenesis of most disorders is unknown, some statements are based on comparative aspects or reflect the authors' opinion.

SOAT1 missense variant in two cats with sebaceous gland dysplasia.

Spontaneously arisen hereditary diseases in domestic animals provide an excellent opportunity to study the physiological functions of the altered genes. We investigated two 4-month-old sibling domestic short haired kittens with dry dark debris around the eyes, nose, and ears, dark crusting on the legs and a thin poor hair coat. Skin biopsies revealed abnormal sebaceous gland morphology with lack of normal sebocyte arrangement and differentiation. Hair follicles had a distorted silhouette, interpreted as a change secondary to the observed sebaceous gland dysplasia. Whole genome sequencing on both affected kittens and 65 genetically diverse feline genomes was performed. Filtering for variants that were present in both kittens but absent from the control genomes revealed a homozygous missense variant in SOAT1, encoding sterol O-acyltransferase 1. The protein is localized in the endoplasmic reticulum and catalyzes the formation of cholesteryl esters, an essential component of sebum and meibum. The identified SOAT1:c.1531G > A variant is predicted to change a highly conserved glycine residue within the last transmembrane domain of SOAT1, p.Gly511Arg. In mice, variants in Soat1 or complete knockout of the gene lead to the "hair interior defect" (hid) or abnormal Meibomian glands, respectively. SOAT1:c.1531G > A represents a plausible candidate variant for the observed sebaceous gland dysplasia in both kittens of this study. The variant was not present in 10 additional cats with a similar clinical and histopathological phenotype suggesting genetic heterogeneity. SOAT1 variants should be considered as potential cause in hereditary sebaceous gland dysplasias of humans and domestic animals.

SDR9C7 missense variant in a Chihuahua with non-epidermolytic ichthyosis.

Ichthyoses represent a heterogeneous group of cornification disorders that are associated with skin barrier defects. We investigated a 9-month-old Chihuahua showing excessive scale formation. Clinical and histopathological examinations revealed non-epidermolytic ichthyosis and a genetic defect was suspected. We therefore sequenced the genome of the affected dog and compared the data with 564 genetically diverse control genomes. Filtering for private variants identified a homozygous missense variant in SDR9C7, c.454C>T or p.(Arg152Trp). SDR9C7 is a known candidate gene for ichthyosis in humans and encodes the short-chain dehydrogenase/reductase family 9C member 7. The enzyme is involved in the production of a functional corneocyte lipid envelope (CLE), a crucial component of the epidermal barrier. Pathogenic variants in SDR9C7 have been described in human patients with autosomal recessive ichthyosis. We assume that the identified missense variant in the affected Chihuahua of this study impairs the normal enzymatic activity of SDR9C7 and thus prevents the formation of a functioning CLE, resulting in a defective skin barrier. To the best of our knowledge, this is the first report of a spontaneous SDR9C7 variant in domestic animals.

Independent DSG4 frameshift variants in cats with hair shaft dystrophy.

Investigations of hereditary phenotypes in spontaneous mutants may help to better understand the physiological functions of the altered genes. We investigated two unrelated domestic shorthair cats with bulbous swellings of the hair shafts. The clinical, histopathological, and ultrastructural features were similar to those in mice with lanceolate hair phenotype caused by loss-of-function variants in Dsg4 encoding desmoglein 4. We sequenced the genomes from both affected cats and compared the data of each affected cat to 61 control genomes. A search for private homozygous variants in the DSG4 candidate gene revealed independent frameshift variants in each case, c.76del or p.Ile26fsLeu*4 in case no. 1 and c.1777del or p.His593Thrfs*23 in case no. 2. DSG4 is a transmembrane glycoprotein located primarily in the extracellular part of desmosomes, a complex of adhesion molecules responsible for connecting the keratin intermediate filaments of neighbouring epithelial cells. Desmosomes are essential for normal hair shaft formation. Both identified DSG4 variants in the affected cats lead to premature stop codons and truncate major parts of the open-reading frame. We assume that this leads to a complete loss of DSG4 function, resulting in an incorrect formation of the desmosomes and causing the development of defective hair shafts. Together with the knowledge on the effects of DSG4 variants in other species, our data suggest that the identified DSG4 variants cause the hair shaft dystrophy. To the best of our knowledge, this study represents the first report of pathogenic DSG4 variants in domestic animals.

A Missense Variant in SLC39A4 in a Litter of Turkish Van Cats with Acrodermatitis Enteropathica.

In a litter of Turkish Van cats, three out of six kittens developed severe signs of skin disease, diarrhea, and systemic signs of stunted growth at 6 weeks of age. Massive secondary infections of the skin lesions evolved. Histopathological examinations showed a mild to moderate hyperplastic epidermis, covered by a thick layer of laminar to compact, mostly parakeratotic keratin. The dermis was infiltrated with moderate amounts of lymphocytes and plasma cells. Due to the severity of the clinical signs, one affected kitten died and the other two had to be euthanized. We sequenced the genome of one affected kitten and compared the data to 54 control genomes. A search for private variants in the two candidate genes for the observed phenotype, MKLN1 and SLC39A4, revealed a single protein-changing variant, SLC39A4:c.1057G>C or p.Gly353Arg. The solute carrier family 39 member 4 gene (SLC39A4) encodes an intestinal zinc transporter required for the uptake of dietary zinc. The variant is predicted to change a highly conserved glycine residue within the first transmembrane domain, which most likely leads to a loss of function. The genotypes of the index family showed the expected co-segregation with the phenotype and the mutant allele was absent from 173 unrelated control cats. Together with the knowledge on the effects of SLC39A4 variants in other species, these data suggest SLC39A4:c.1057G>C as candidate causative genetic variant for the phenotype in the investigated kittens. In line with the human phenotype, we propose to designate this disease acrodermatitis enteropathica (AE).

A KRT71 Loss-of-Function Variant Results in Inner Root Sheath Dysplasia and Recessive Congenital Hypotrichosis of Hereford Cattle.

Genodermatoses, such as heritable skin disorders, mostly represent Mendelian conditions. Congenital hypotrichosis (HY) characterize a condition of being born with less hair than normal. The purpose of this study was to characterize the clinicopathological phenotype of a breed-specific non-syndromic form of HY in Hereford cattle and to identify the causative genetic variant for this recessive disorder. Affected calves showed a very short, fine, wooly, kinky and curly coat over all parts of the body, with a major expression in the ears, the inner part of the limbs, and in the thoracic-abdominal region. Histopathology showed a severely altered morphology of the inner root sheath (IRS) of the hair follicle with abnormal Huxley and Henle's layers and severely dysplastic hair shafts. A genome-wide association study revealed an association signal on chromosome 5. Homozygosity mapping in a subset of cases refined the HY locus to a 690 kb critical interval encompassing a cluster of type II keratin encoding genes. Protein-coding exons of six positional candidate genes with known hair or hair follicle function were re-sequenced. This revealed a protein-changing variant in the KRT71 gene that encodes a type II keratin specifically expressed in the IRS of the hair follicle (c.281delTGTGCCCA; p.Met94AsnfsX14). Besides obvious phenocopies, a perfect concordance between the presence of this most likely pathogenic loss-of-function variant located in the head domain of KRT71 and the HY phenotype was found. This recessive KRT71-related form of hypotrichosis provides a novel large animal model for similar human conditions. The results have been incorporated in the Online Mendelian Inheritance in Animals (OMIA) database (OMIA 002114-9913).

Transcriptional Differences between Canine Cutaneous Epitheliotropic Lymphoma and Immune-Mediated Dermatoses.

Canine cutaneous epitheliotropic T-cell lymphoma (CETL) and immune-mediated T-cell predominant dermatoses (IMD) share several clinical and histopathological features, but differ substantially in prognosis. The discrimination of ambiguous cases may be challenging, as diagnostic tests are limited and may prove equivocal. This study aimed to investigate transcriptional differences between CETL and IMD, as a basis for further research on discriminating diagnostic biomarkers. We performed 100bp single-end sequencing on RNA extracted from formalin-fixed and paraffin-embedded skin biopsies from dogs with CETL and IMD, respectively. DESeq2 was used for principal component analysis (PCA) and differential gene expression analysis. Genes with significantly different expression were analyzed for enriched pathways using two different tools. The expression of selected genes and their proteins was validated by RT-qPCR and immunohistochemistry. PCA demonstrated the distinct gene expression profiles of CETL and IMD. In total, 503 genes were upregulated, while 4986 were downregulated in CETL compared to IMD. RT-qPCR confirmed the sequencing results for 5/6 selected genes tested, while the protein expression detected by immunohistochemistry was not entirely consistent. Our study revealed transcriptional differences between canine CETL and IMD, with similarities to human cutaneous lymphoma. Differentially expressed genes are potential discriminatory markers, but require further validation on larger sample collections.

A complex histopathological challenge: suspicion of an osteoblastoma-like osteosarcoma arising from the second thoracic vertebra in a cat.

BACKGROUND: Reports of osteoblastic tumours are limited to a few case reports in veterinary medicine. Osteoblastoma-like osteosarcoma has been accepted by the World Health Organization as an intermediate form between an osteosarcoma and osteoblastoma. This type of tumour indicates an osteosarcoma, that may resemble osteoblastoma clinically, histologically, and radiologically and have the capability for metastasis. Osteoblastoma-like osteosarcoma has not been described in veterinary medicine so far. CASE PRESENTATION: An eight-year old cat was presented due to progressive ataxia and paraparesis of the pelvic limbs. Imaging confirmed a well-defined, extradural mass originating from the spinous process of the second thoracic vertebra (T2) leading to severe compression of the spinal cord. Decompressive cytoreduction was achieved by removal of the mass after dorsal laminectomy of T1. After recovering from an acute worsening 3.5 weeks after surgery, the cat had an improved neurological status and the dorsal compression was resolved at follow-up 8 months later. A focal contrast enhancing lesion was still evident at the base of T2 spinous process and lung metastasis was additionally suspected. Based on histopathological, radiographic, and clinical features, an "osteoblastoma-like osteosarcoma" was suspected. CONCLUSIONS: To the best of our knowledge, this is the first description of this tumour in veterinary medicine. In addition, this case report highlights the difficulty in the diagnosis and definition of osseous neoplasia in cats and provides a literature review.

Canine Epithelial Skin Tumours: Expression of the Stem Cell Markers Lgr5, Lgr6 and Sox9 in Light of New Cancer Stem Cell Theories.

Evidence is accumulating that tumour development is driven by cancer stem cells (CSCs). In order to understand the presence and potential contribution of stem cells (SCs) as tumour-initiating cells in canine cutaneous tumours, we selected three putative SC markers (Lgr5, Lgr6 and Sox9) and investigated their expression pattern, level of protein and mRNA expression, in 43 canine hair follicle (HF) and 18 canine cutaneous epidermal tumours by immunohistochemistry and qRT-PCR, using normal skin samples as controls. Lgr5 protein expression was not detected in epidermal and HF tumours; however, Lgr5 mRNA overexpression was evident in some HF tumours. Sox9 was expressed in several tumour cases, both at the protein and mRNA level. The Lgr6 antibody tested was not suitable for formalin-fixed paraffin-embedded tissue samples, but Lgr6 gene showed higher expression in several samples of both HF and epidermal tumours compared with normal skin. Significantly higher mRNA expression levels of the three SC markers were found in trichoblastomas (TB) compared with basal cell carcinomas (BCC). The present results indicated that canine HF and epidermal tumours might have common tumour-initiating cells. The mRNA expression of the three selected SC markers, especially Lgr5, could be potentially useful in the distinction between canine TB and BCC.

ATP2A2 SINE Insertion in an Irish Terrier with Darier Disease and Associated Infundibular Cyst Formation.

A 4-month-old female Irish Terrier presented with a well demarcated ulcerative and crusting lesion in the right ear canal. Histological analysis revealed epidermal hyperplasia with severe acantholysis affecting all suprabasal layers of the epidermis, which prompted a presumptive diagnosis of canine Darier disease. The lesion was successfully treated by repeated laser ablation of the affected epidermis. Over the course of three years, the dog additionally developed three dermal nodules of up to 4 cm in diameter that were excised and healed without complications. Histology of the excised tissue revealed multiple infundibular cysts extending from the upper dermis to the subcutis. The cysts were lined by squamous epithelium, which presented with abundant acantholysis of suprabasal keratinocytes. Infundibular cysts represent a novel finding not previously reported in Darier patients. Whole genome sequencing of the affected dog was performed, and the functional candidate genes for Darier disease (ATP2A2) and Hailey-Hailey disease (ATP2C1) were investigated. The analysis revealed a heterozygous SINE insertion into the ATP2A2 gene, at the end of intron 14, close to the boundary of exon 15. Analysis of the ATP2A2 mRNA from skin of the affected dog demonstrated a splicing defect and marked allelic imbalance, suggesting nonsense-mediated decay of the resulting aberrant transcripts. As Darier disease in humans is caused by haploinsufficiency of ATP2A2, our genetic findings are in agreement with the clinical and histopathological data and support the diagnosis of canine Darier disease.

Abnormal keratinocyte differentiation in the nasal planum of Labrador Retrievers with hereditary nasal parakeratosis (HNPK).

Hereditary nasal parakeratosis (HNPK) is an inherited disorder described in Labrador Retrievers and Greyhounds. It has been associated with breed-specific variants in the SUV39H2 gene encoding a histone 3 methyltransferase involved in epigenetic silencing. Formalin-fixed biopsies of the nasal planum of Labrador Retrievers were screened by immunofluorescence microscopy for the presence and distribution of epidermal proliferation and differentiation markers. Gene expression of these markers was further analysed using RNA sequencing (RNA-seq) and ultrastructural epidermal differences were investigated by electron microscopy. Differentiation of the nasal planum in the basal and suprabasal epidermal layers of HNPK-affected dogs (n = 6) was similar compared to control dogs (n = 6). In the upper epidermal layers, clear modifications were noticed. Loricrin protein was absent in HNPK-affected nasal planum sections in contrast to sections of the same location of control dogs. However, loricrin was present in the epidermis of paw pads and abdominal skin from HNPK dogs and healthy control dogs. The patterns of keratins K1, K10 and K14, were not markedly altered in the nasal planum of HNPK-affected dogs while the expression of the terminal differentiation marker involucrin appeared less regular. Based on RNA-seq, LOR and IVL expression levels were significantly decreased, while KRT1, KRT10 and KRT14 levels were up-regulated (log2fold-changes of 2.67, 3.19 and 1.71, respectively) in HNPK-affected nasal planum (n = 3) compared to control dogs (n = 3). Electron microscopical analysis revealed structural alterations in keratinocytes and stratum corneum, and disrupted keratinocyte adhesions and distended intercellular spaces in lesional samples (n = 3) compared to a sample of a healthy control dog (n = 1). Our findings demonstrate aberrant keratinocyte terminal differentiation of the nasal planum of HNPK-affected Labrador Retrievers and provide insights into biological consequences of this inactive SUV39H2 gene variant.

Is a de novo nonsense variant in the ASPDH gene the cause of ulcerative skin lesions in a Holstein calf?

BACKGROUND: Genetic skin diseases in cattle are rare. CLINICAL SUMMARY: A 7-week-old female Holstein calf was presented with epidermal lesions and alopecia in the caudal region of the ears and on the neck, as well as deep bilateral ulcerative lesions on the palmar aspect of the metacarpi and dorsal aspect of the right metacarpus. Clinical, pathological and histopathological examination of the calf was suggestive of a subepidermal vesicular dermatosis. Genetic analysis identified a de novo non-sense variant affecting the aspartate dehydrogenase domain containing (ASPDH) gene, which might be associated with the formation of subepidermal vesicles in this case. CONCLUSION AND CLINICAL IMPORTANCE: The observed phenotype in the calf may represent a novel form of a vesicular skin disorder. Haploinsufficiency of the ASPDH gene might be considered as a possible cause.

Clonality testing as complementary tool in the assessment of different patient groups with canine chronic enteropathy.

Differentiation between canine chronic enteropathy (CCE) and intestinal lymphoma is a diagnostic challenge as histopathology might fail to yield unequivocal results. Detection of clonal rearrangements of the T-cell-receptor gamma (TCRG) chain and IG heavy chain (IGH) V-J genes offer a useful solution. In this retrospective study, histopathology samples of 35 CCE patients and 7 healthy Beagle dogs underwent clonality testing. Patients suffered either from inflammatory bowel disease (IBD), food responsive diarrhea (FRD) or protein loosing enteropathy secondary to IBD (PLE/IBD). Healthy Beagles served as controls (CO). Canine IBD activity index (CIBDAI) and histopathological WSAVA-grading differed significantly (p<0.001) between groups. CIBDAI improved significantly after appropriate therapy (p < 0.0001). Intestinal biopsies of all CO showed polyclonal patterns for B- and T-cell primers. All samples from CCE patients showed polyclonal patterns for the B-cell primers. Targeting TCRG, 4 patients showed a monoclonal or oligoclonal pattern of the lymphocytic infiltrates in the duodenum and/or colon. Clinical improvement was observed in all dogs. Although a small cell lymphoma cannot be excluded in view of the short follow up duration, a false positive result, in the sense of a canonical rearrangement or unspecific amplification due to a antigenic stimulation in a non-neoplastic inflammatory process is possible.

Mycobacterium nebraskense infection in a dog in Switzerland with disseminated skin lesions.

BACKGROUND: Cutaneous disseminated mycobacteriosis is rare in dogs. To the best of the authors' knowledge, the slowly growing mycobacterial species Mycobacterium nebraskense has not been described before in this species. OBJECTIVE: Description of clinical features, laboratory analyses and treatment regimen of this unusual case. ANIMAL: A 9-year-old female-spayed West Highland white terrier dog presented with progressive nodules and ulcerations on both sides of the thorax and the rostral aspect of the chest. METHODS AND MATERIALS: Investigations involved histopathological examination of skin biopsies (including special stains for fungi, bacteria and mycobacteria), standard and mycobacterial culture (including susceptibility testing), 16S/23S rRNA sequencing and BLAST similarity searching. RESULTS: Ziehl-Neelsen staining of decontaminated biopsy material revealed acid-fast bacteria morphologically consistent with mycobacteria. Treatment with clarithromycin and marbofloxacin achieved partial resolution. A change in the treatment regimen to pradofloxacin and azithromycin resulted in rapid deterioration of skin lesions. Final healing occurred with the addition of prednisolone at an anti-inflammatory dose. The results of mycobacterial culture and susceptibility testing were received 10 and 12 months, respectively, after the first presentation of the dog. Therapy was stopped after 16 months without recurrence of skin lesions. CONCLUSIONS AND CLINICAL IMPORTANCE: This case is noteworthy for the description of a new mycobacterial species contributing to disseminated panniculitis in a dog and for the difficulties experienced in the lengthy empirical treatment of slowly growing nontuberculous mycobacterial infections. The addition of prednisolone to induce complete healing raises the question of whether the mycobacterial infection was primary or whether it occurred secondarily to an ongoing sterile panniculitis.

Genetic variant in the NSDHL gene in a cat with multiple congenital lesions resembling inflammatory linear verrucous epidermal nevi.

BACKGROUND: The feline counterpart of human inflammatory linear verrucous epidermal nevus (ILVEN) has been described; however, the possible underlying developmental defect has not been investigated. OBJECTIVE: To report a case of multiple ILVEN-like lesions in a cat with a genetic variant in the NSDHL gene. ANIMALS: A 2-year-old, female, domestic short hair cat with a history of multiple alopecic, verrucous, hyperpigmented and erythematous skin lesions, following Blaschko's lines on the head, the limbs, the trunk and paw pads. METHODS AND RESULTS: According to the clinical and histopathological findings, a diagnosis of multiple ILVEN-like lesions was made. Genetic investigation revealed a heterozygous missense variant in the X-chromosomal NSDHL gene predicted to lead to a loss-of-function of the NSDHL protein. CONCLUSIONS AND CLINICAL IMPORTANCE: To the best of the authors' knowledge, this is the first case of feline ILVEN-like lesions in which a genetic cause has been proposed. Future studies to establish a causal relationship between NSDHL variants and skin lesions might lead to pathogenesis-directed treatments.

Detection and Characterization of Okapi (Okapia johnstoni)-specific Papillomavirus type 1 (OjPV1).

Papillomavirus-specific DNA was detected in skin lesions collected from an okapi (Okapia johnstoni) in the Zoo Basel. According to the nucleotide sequence analysis, the virus belongs to the genus Deltapapillomavirus. Based on bioinformatics analysis, we propose to designate the newly identified virus as Okapia johnstoni Papillomavirus type 1 (OjPV1). OjPV1 is genetically most closely related to a recently described giraffe (Giraffa camelopardalis) -specific papillomavirus (GcPV1). Of note, the putative oncogenic E5 proteins from OjPV1 and GcPV1 are more conserved than the L1 proteins. This indicates, that the selection pressure on E5 may be more pronounced than that on the otherwise most conserved major capsid protein L1.

Cutaneous Tumors in Swiss Dogs: Retrospective Data From the Swiss Canine Cancer Registry, 2008-2013.

Data collected in animal cancer registries comprise extensive and valuable information, even more so when evaluated in context with precise population data. The authors evaluated 11 740 canine skin tumors collected in the Swiss Canine Cancer Registry from 2008-2013, considering data on breed, sex, age, and anatomic locations. Their incidence rate (IR) per 100 000 dogs/year in the Swiss dog population was calculated based on data from the official and mandatory Swiss dog registration database ANIS. The most common tumor types were mast cell tumors (16.35%; IR, 60.3), lipomas (12.47%; IR, 46.0), hair follicle tumors (12.34%; IR, 45.5), histiocytomas (12.10%; IR, 44.6), soft tissue sarcomas (10.86%; IR, 40.1), and melanocytic tumors (8.63%; IR, 31.8) with >1000 tumors per type. The average IR of all tumor types across the 227 registered breeds was 372.2. The highest tumor incidence was found in the Giant Schnauzer (IR, 1616.3), the Standard Schnauzer (IR, 1545.4), the Magyar Vizsla (IR, 1534.6), the Rhodesian Ridgeback (IR, 1445.0), the Nova Scotia Duck Tolling Retriever (IR, 1351.7), and the Boxer (IR, 1350.0). Mixed-breed dogs (IR, 979.4) had an increased IR compared to the average of all breeds. Previously reported breed predispositions for most tumor types were confirmed. Nevertheless, the data also showed an increased IR for mast cell tumors and melanocytic tumors in the Nova Scotia Duck Tolling Retriever and for histiocytomas in the Flat Coated Retriever. The results from this study can be taken into consideration when selecting purebred dogs for breeding to improve a breed's health.

Magnetic Resonance Imaging Signal Alterations in Paraspinal Muscles in Dogs with Acute Thoracolumbar Intervertebral Disk Extrusion.

Muscle signal alteration detected on MRI is seen in diverse pathologic conditions. We observed signal alterations within the paraspinal muscles in dogs with acute thoracolumbar intervertebral disk extrusion. The aim of this retrospective study was to describe MRI features of paraspinal muscle signal alteration in dogs with acute thoracolumbar intervertebral disk extrusion and to investigate an association of the signal alterations with neurological grade, type and location of intervertebral disk extrusion, degree of spinal cord compression, and presence of epidural hemorrhage. Medical records of dogs undergoing MRI because of thoracolumbar intervertebral disk extrusion between August 2014 and June 2016 were reviewed. MRI was evaluated for SI changes within the paravertebral musculature, their location, extension, affected muscles, contrast enhancement, and signal void in T2* sequences. Intervertebral disk herniation was categorized as acute non-compressive nucleus pulposus extrusion (ANNPE) or compressive intervertebral disk disease. In five patients, muscle biopsies of areas with signal intensity changes were taken during surgery. In total, 103 dogs were enrolled in the study. Paraspinal muscle signal alterations were visible in 37 dogs (36%) affecting the epaxial musculature (n = 17), hypaxial musculature (n = 12), or both (n = 8). All signal alterations were hyperintense on T2-weighted images and iso- or hypointense in T1-weighted images. Signal void in T2* was not observed in any dog. Postcontrast sequences were available in 30 of the 37 dogs and showed enhancement in 45%. There was neither an association with degree of compression nor epidural hemorrhage. Intervertebral disk extrusion caudal to L1 and a higher neurological grade was associated with the presence of muscle changes. Histopathology revealed mild to moderate acute muscle fiber degeneration with edema and necrosis in three of five samples. The MRI, as well as the muscle samples, show rather unspecific changes. The underlying pathomechanism might be related to ischemia or muscle spasm, but also denervation edema may explain the signal alteration.

A de novo germline mutation of DLX3 in a Brown Swiss calf with tricho-dento-osseus-like syndrome.

OBJECTIVE: A novel congenital disorder affecting a calf was observed, and its phenotype and genetic mutation identified. ANIMAL: A six-month-old female Brown Swiss calf. METHODS: Diagnostic investigation and whole genome sequencing of a case parent trio was performed. RESULTS: The calf had a dull kinky coat with mild hypotrichosis, and teeth with brown staining and enamel defects. Histological examination of skin biopsies was compatible with a follicular dysplasia. Radiography and computed tomography revealed thickening of the skull bones and large pulp cavities with a marked thinning of enamel affecting all teeth. A de novo germline mutation affecting the distal-less homeobox gene (DLX3) was identified. The 10 bp frameshift mutation in exon 3 of the bovine DLX3 gene is predicted to replace the second C-terminal transactivation domain of the wild-type protein by a recoded peptide of 99 amino acids without any sequence similarity. CONCLUSION AND CLINICAL IMPORTANCE: A causative mutation for a sporadic phenotype resembling human tricho-dento-osseous syndrome was identified after detection of a de novo germline mutation in the DLX3 gene.

A Large Deletion in the NSDHL Gene in Labrador Retrievers with a Congenital Cornification Disorder.

In heterozygous females affected by an X-linked skin disorder, lesions often appear in a characteristic pattern, the so-called Blaschko's lines. We investigated a female Labrador Retriever and her crossbred daughter, which both showed similar clinical lesions that followed Blaschko's lines. The two male littermates of the affected daughter had died at birth, suggesting a monogenic X-chromosomal semidominant mode of inheritance. Whole genome sequencing of the affected daughter, and subsequent automated variant filtering with respect to 188 nonaffected control dogs of different breeds, revealed 332 hetero-zygous variants on the X-chromosome private to the affected dog. None of these variants was protein-changing. By visual inspection of candidate genes located on the X-chromosome, we identified a large deletion in the NSDHL gene, encoding NAD(P) dependent steroid dehydrogenase-like, a 3ß-hydroxysteroid dehydrogenase involved in cholesterol biosynthesis. The deletion spanned >14 kb, and included the last three exons of the NSDHL gene. By PCR and fragment length analysis, we confirmed the presence of the variant in both affected dogs, and its absence in 50 control Labrador Retrievers. Variants in the NSDHL gene cause CHILD syndrome in humans, and the bare patches (Bpa) and striated (Str) phenotypes in mice. Taken together, our genetic data and the known role of NSDHL in X-linked skin disorders strongly suggest that the identified structural variant in the NSDHL gene is causative for the phenotype in the two affected dogs.