Clinical, histopathological and genetic data of ichthyosis in the golden retriever: a prospective study

O bjectives : We described epidemiological, clinical, histopathological and ultrastructural features of ichthyosis in the golden retriever breed in a prospective study. We also investigated the mode of transmission of this disease.
M aterials and M ethods : We examined 150 golden retrievers, 73 of which were affected by ichthyosis (35 males and 38 females). We carried out detailed clinical and histopathological examinations for 40 affected dogs. Transmission electron microscopy was performed for two of them. We used pedigree analysis with the Cyrillic software to determine the mode of transmission.
R esults : Dermatological signs included a mild to moderate or severe generalised scaling with initially small to large whitish scales and progressively blackish scales. The ventral glabrous skin was hyperpigmented and rough, similar to sandpaper. Histopathological features were characterised by moderate to severe laminated or compact orthokeratotic epidermal hyperkeratosis without significant involvement of the stratum granulosum. Ultrastructural findings revealed laminated or compact keratin layers and numerous persistent corneodesmosomes within the stratum corneum. Analysis of the pedigree suggested an autosomal recessive inheritance.
C onclusion : The histopathological and ultrastructural characteristics strongly suggest that golden retriever ichthyosis is a retention ichthyosis, caused by absence of corneodesmosomal degradation, transmitted through an autosomal recessive mode.     

Congenital ichthyosis in a llama

A 1-month-old male cria was examined because of diffuse hyperkeratosis and conjunctivitis that had existed since birth. The mucocutaneous junction of the nostrils as well as the neck, coronary bands, and axillary and inguinal regions were the most severely affected areas. Orthokeratosis involving the epidermis and follicular infundibula was observed on skin biopsy specimens. Electron microscopy revealed 4 to 6 granular layers and inter- and intracellular vacuolation in the stratum corneum; diagnosis of ichthyosis was established.     

Electron microscopic observations of stratum corneum intercellular lipids in normal and atopic dogs.

The barrier function of mammalian skin is maintained by intercellular stratum corneum lipids. In human patients with atopic dermatitis, an abnormal lipid barrier results in dry skin and increased transepidermal water loss. At this time, it is not known if a defective lipid barrier is present in atopic dogs. Normal and atopic canine skin were postfixed in ruthenium tetroxide and studied using transmission electron microscopy to determine structural differences within stratum corneum lipids. Intercellular lipid lamellae were graded on a semiquantitative scale. The deposition of stratum corneum lipid lamellae in atopic canine skin appeared markedly heterogeneous compared with that seen in normal canine skin. When present, the lamellae often exhibited an abnormal structure. The continuity and thickness of the intercellular lipid lamellae were significantly less in nonlesional atopic than in normal canine skin. These preliminary observations suggest that the epidermal lipid barrier is defective in atopic canine skin. Additional studies are needed to further characterize the biochemical defect and to possibly correct it with nutritional and/or pharmacologic intervention.     

Cutaneous inverted papillomas in dogs

Inverted papillomas of the skin occurred in five dogs. Lesions were 1-2 cm, circumscribed, flask-like structures below the level of the surrounding normal skin. Walls of the structures consisted of hyperplastic epidermis, forming thin papillary projections on thin fibrovascular stalks. Cells in the stratum granulosum had clear cytoplasm, numerous keratohyalin-like granules of various sizes, and poorly defined intranuclear inclusions. These cells stained positively for papillomavirus group-specific antigens by both the peroxidase-antiperoxidase and avidin-biotin methods. Virions with a mean diameter of 35.7 nm were present within nuclei in cells of the stratum granulosum when examined by electron microscopy. In situ DNA hybridization, using a canine oral papillomavirus probe, localized papillomavirus DNA in canine oral papillomas, but not in canine cutaneous squamous or inverted papillomas, suggesting that a different papillomavirus type was present in the latter lesions. Although these lesions resembled intracutaneous cornifying epitheliomas (keratoacanthomas), they appear to be a distinct lesion, probably with a different etiology.     

The stratum corneum: the rampart of the mammalian body

Background –  The stratum corneum (SC) is the outermost region of the epidermis and plays key roles in cutaneous barrier function in mammals. The SC is composed of ‘bricks’, represented by flattened, protein‐enriched corneocytes, and ‘mortar’, represented by intercellular lipid‐enriched layers. As a result of this ‘bricks and mortar’ structure, the SC can be considered as a ‘rampart’ that encloses water and solutes essential for physiological homeostasis and that protects mammals from physical, chemical and biological assaults. Structures and functions –  The corneocyte cytoskeleton contains tight bundles of keratin intermediate filaments aggregated with filaggrin monomers, which are subsequently degraded into natural moisturizing compounds by various proteases, including caspase 14. A cornified cell envelope is formed on the inner surface of the corneocyte plasma membrane by transglutaminase‐catalysed cross‐linking of involucrin and loricrin. Ceramides form a lipid envelope by covalently binding to the cornified cell envelope, and extracellular lamellar lipids play an important role in permeability barrier function. Corneodesmosomes are the main adhesive structures in the SC and are degraded by certain serine proteases, such as kallikreins, during desquamation. Clinical relevance –  The roles of the different SC components, including the structural proteins in corneocytes, extracellular lipids and some proteins associated with lipid metabolism, have been investigated in genetically engineered mice and in naturally occurring hereditary skin diseases, such as ichthyosis, ichthyosis syndrome and atopic dermatitis in humans, cattle and dogs.     

The clinical and morphologic features of nonepidermolytic ichthyosis in the golden retriever

A scaling disorder specific to Golden Retriever dogs has been recognized by both dermatologists and pathologists, but to date has not been well characterized. At the University of Pennsylvania's Laboratory of Toxicology and Pathology, 46 cases of ichthyosis were diagnosed histologically in Golden Retriever dogs from January 2004 to January 2007. A total of 22 dogs had skin lesions documented at younger than 1 year of age; 3 dogs between 1 and 2 years of age; 13 dogs developed lesions at older than 2 years; and the time of onset was unknown for 8 dogs. A total of 25 dogs were female, and 21 were male. All dogs had strikingly similar histopathologic changes that consisted of mild to moderate laminar orthokeratotic hyperkeratosis with an absence of epidermal hyperplasia and dermal inflammation. Ultrastructural analysis using a ruthenium tetroxide fixation method was performed on punch biopsy samples from 5 dogs and compared with 2 control dogs (1 clinically and histologically normal sibling of an affected dog and 1 Cairn Terrier). All affected dogs had retained and convoluted membranes with crystalline structures in the stratum corneum. Scattered keratinocytes in the granular cell layer had prominent, clear, membrane-bound, cytoplasmic vacuoles. Pedigree analysis of 14 dogs was compatible with autosomal recessive inheritance, but incomplete dominance could not be ruled out. This unique hyperkeratotic/scaling disorder in Golden Retrievers has distinctive clinical, histologic, and ultrastructural features, which are consistent with a primary cornification defect.     

Light and electron microscopic comparisons of cutaneous fibromas in white-tailed and mule deer

Cutaneous fibromas of white-tailed deer (Odocoileus virginianus), when compared with normal skin of the same species, had a thinner basement membrane; thickened stratum spinosum with numerous melanocytes, desmosomes, polyribosomes, and tonofilaments; focal hyperplasia of the stratum granulosum containing numerous large, electron-dense keratohyalin granules with irregular borders and containing occasional cells with diffuse intranuclear virus particles; and a moderately thickened stratum corneum with (although rarely) small crystalline arrays of virus particles. Normal mule deer (Odocoileus hemionus) skin was structurally similar to that of the white-tailed deer. Mule deer fibromas were similar to those in white-tailed deer, except for diffuse thickening of the stratum granulosum (the cells of which contained large keratohyalin granules of various electron densities with occasional composite granules) and except for a markedly thickened stratum corneum that contained numerous intranuclear viral inclusions. In negatively stained homogenates of tumors from both deer species, viral particles resembled papillomaviruses.     

Pathogenesis and electron microscopic changes of spherulogenesis of Coccidioides immitis (valley fever)

Pathogenesis and electron microscopic changes of spherulogenesis of Coccidioides immitis were determined. The organism showed a strong affinity for lung tissue, with granuloma developing in 100% (n = 40) of animals after subcutaneous and intraperitoneal inoculation. Intranasal instillation of the arthrospores resulted in moderate granuloma, with a markedly low frequency rate of infection in 11 animals (55%). Intradermal inoculation and skin scarification did not induce systemic infection. Unlike other routes used to induce infection, only 30% of the mice showed cutaneous changes, whereas in the group infected by skin scarification, 25% of the animals revealed pathologic changes. Indurated tiny nodular lesions developed in the skin at the site of the inoculation. The lesions did not ulcerate, and complete resolution was observed in 4 to 6 weeks. Electron microscopy of the spherulogenesis showed that the tissue form of the fungus replicated in the host tissues by segmentation of the innermost stratum of the wall of the spherule. The layer appeared to function as a germinating center, and as many as 8 spores of irregular size and shape were produced within a kidney-shaped segment. Many segments were in each spherule. The spores were separated, pushed more centrally, and became rounded to become the endospores. When the endospores were freed, each developed into a spherule.     

Kartagener's syndrome in an old miniature poodle

A 12-year old male miniature poodle with a chronic progressive cough of two years duration was found to have situs inversus totalis, rhinitis, bronchiectasis and bronchopneumonia with metaplasia. Clinical and pathological findings satisfy the clinical criteria for a diagnosis of Kartagener's syndrome. However, the dog had no history of respiratory disease during it's first year of life, it sired at least one healthy puppy and electron microscopic examination of tracheal cilia showed only minimal microtubular abnormalities. This is the first report of a miniature poodle with Kartagener's syndrome. Kartagener's syndrome and mild forms of primary ciliary dyskinesia (PCD) may play an important role in the development of chronic respiratory disease in older dogs.     

Experimental bovine Trichophyton verrucosum infection. Comparison of the rate of epidermal cell proliferation and keratinisation in non-infected and reinoculated cattle.

The rate of epidermal cell renewal in normal bovine skin and that reinoculated with Trichophyton verrucosum was measured using a radioautographic technique. The transit times of both nucleated and fully keratinised cells were measured in sequential biopsy samples removed at predetermined periods after intradermal inoculation with radio-labelled isotopes. The total time taken for cells of the basal layer to travel to the point of desquamation in the stratum corneum was 18 days in normal cattle. In similar areas on cattle that had been reinoculated with T verrucosum the total epidermal cell renewal time was reduced to 12 days. Increased protein synthesis, as measured by incorporation of radio-labelled nucleoside was evident in basal cells within 24 h of reinoculation with the fungus. The nucleated epidermal cell thickness had almost doubled in areas of reinoculated skin within 72 h and increased cell proliferation was maintained for at least 10 days. Desquamation of the thickened stratum corneum had occurred within seven days of reinoculation with the fungus.     

Papilloma-like virus infection in Bolivian side-neck turtles

Five Bolivian side-neck turtles had multifocal small, round to confluent, white skin lesions distributed over the head. Several gram-negative microorganisms were isolated from the lesions. Light microscopy revealed hyperkeratosis and hyperplasia of the epidermis. Ultrastructural evaluation demonstrated crystalline aggregates of virus particles within nuclei of cells in the stratum granulosum and free within the stratum corneum. On the basis of size, location, arrangement, and tissue affected, the particles resembled papillomaviruses.     

Psoriatic plaques in Macaca fascicularis

An adult male cynomolgus monkey (Macaca fascicularis) developed erythematous plaques with adherent white scales on the skin. Microscopically, the epidermis had regular acanthosis with marked parakeratosis, focal absence of stratum granulosum, and spongiform pustules and Munro-like microabscesses. These histologic findings were suggestive of psoriasis vulgaris.     

A triad of bovine inherited diseases (abstract)

Three inherited diseases of cattle seen in the past 2 years were described. Familial acantholysis of Angus cattle was seen in 9/54 calves born to cows inadvertently mated to a full sibling bull. Sloughing skin from the joints, nose and palate were seen at 1 day of age, confirmed as suprabasilar clefts on histopathology. A 2-year-old Charolais steer was noted at ante-mortem slaughter inspection with a whole body tremor and nystagmus. Histopathologically, eosinophilic plaques expanded white matter throughout the brain, consistent with a syndrome of 'progressive ataxia' of Charolais cattle. Two calves born from Red Devon cattle had marked hyperkeratosis, microtia and periocular reddening with deep fissuring of the keratin, characteristic of congenital ichthyosis.     

Notoedric mange in two free-ranging North American racoons (Procyon lotor) in Japan

Mange was diagnosed in two North American racoons (Procyon lotor) at Kamakura City in Kanagawa Prefecture, Japan. The mites were identified morphologically as Notoedres cati. Mite infestation affected the skin over the extremities and tail, and was characterized by moderate alopecia and erythematous dermatosis. Histopathologically, the affected skin showed marked epidermal hyperplasia and mites located within the parakeratotic stratum corneum. A slight dermal inflammatory response consisting principally of mononuclear cells was observed. N. cati mites were demonstrated in their tunnels using scanning electron microscopy (SEM). This is the first report of notoedric mange in racoons.     

Ichthyosis in two Chianina calves

The occurrence of ichthyosis in two Italian Chianina calves is described for the first time. Both animals, affected by ichthyosis fetalis and ichthyosis congenita, respectively, showed diffuse cutaneous thickening which had been present since birth. The first patient was a three-month-old female calf; inelastic leather cuirass-like skin associated with generalized hypotrichosis and local alopecia, delay of the physiologic change of coat colour, stiff movement and growth retardation were the most prominent clinical characteristics. The patient was kept under observation for almost one year. The second case occurred in a 18-day-old female calf which was referred to our clinic after it had already died; the presence of irregular hyperkeratotic plates separated by deep fissures over the entire cutaneous surface and the slight eversion of the mucocutaneous junction (eclabium and ectropion) were the most characteristic alterations. In both cases, the major histopathological feature was a diffuse lamellar orthokeratotic hyperkeratosis. An underlying genetic defect was strongly suspected on the basis of a common ancestor for the two sires of the affected calves and of the current scientific knowledge.     

Harlequin ichthyosis in a HanWoo calf

Ichthyosis (fish scale disease) is a rare hereditary disease and characterized by excessive cutaneous scale formation. A male HanWoo calf born by natural service was found with fissures and thickened, scaly, cutaneous plates covering over 90% of its body. Histopathological feature was excess compact orthokeratotic hyperkeratosis involving surface of the epidermis and follicular epithelia. The calf had small malformed ears, ectropion, eclabium and an abnormal nose. Gross and histopathologic findings in calf were consistent with those of harlequin ichthyosis, and it was the first observed harlequin ichthyosis in HanWoo cattle.     

Lectin histochemistry on squamous metaplasia in different epithelial tumors of dogs.

Biotinylated lectins and avidin-biotin-peroxidase complex were used to study the correlation between cellular glycoconjugates' expression and squamous maturation in normal canine skin and in various epithelial neoplasms. Normal skin tissue was obtained from five, male, random-source dogs, 5 to 7 years old. The tumors tested, selected from the files of our Department, were fifteen squamous cell carcinomas from different tissue origin, five hepatoid perianal gland adenocarcinomas with squamous metaplasia, and fourteen solid mammary carcinomas with and without histologic evidence of squamous metaplasia. Except for mammary gland carcinomas, all tumors had been surgically excised from male dogs. Intermediate filament aggregation of twelve solid mammary gland carcinomas were studied electron microscopically. The basal and the lower spinous cells in normal skin and the less differentiated cells in squamous cell carcinomas stained moderately with Griffonia simplicifolia agglutinin-I. Spinous and granular cell layers stained strongly with Phytolacca americana mitogen and Arachis hypogaea agglutinin. Both lectins stained well-differentiated cells in squamous cell carcinomas. The electron microscopic study carried out in solid carcinomas of mammary glands revealed some relationship between the presence of intracytoplasmic tonofibrils and the binding of Griffonia simplicifolia agglutinin-I and Phytolacca americana mitogen to the tumors tested. Our results suggest that the glycosylation pattern occurring during normal keratinocyte differentiation is conserved in squamous cell carcinomas and that Griffonia simplicifolia agglutinin-I and Phytolacca americana mitogen may represent useful tools in distinguishing poorly differentiated squamous cell carcinomas from other poorly differentiated mammary epithelial tumors.     

Sarcoptic mange in free-ranging raccoon dogs (Nyctereutes procyonoides) in Japan

Sarcoptes scabiei infestation was diagnosed in three freshly dead free-ranging raccoon dogs (Nyctereutes procyonoides) in Kanagawa Prefecture, Japan. The dogs presented with an alopecic pruritic skin disease, with signs of alopecia on the ears, muzzle, around the eyes, elbow, thigh and the neck, and hyperpigmented and crusted skin lesions, which had a severe malodour. Skin scrapings revealed the presence of the mite Sarcoptes scabiei. Histopathology of lesions demonstrated marked acanthosis, hyperkeratosis, parakeratosis and fungal elements, which were subsequently identified as Acremonium sp., Alternaria sp. and an unknown fungus. Mite segments were located mainly in the stratum corneum and also in the stratum granulosum. Tunnels could be observed in the hyperkeratotic stratum corneum. Scanning electron microscopy (SEM) revealed the tortoise-like Sarcoptes scabiei with four long bristles, suckers and blade-like claws on legs 1 and 2, cuticular spines, prominent body striations and a terminal anus. SEM also revealed an adult female mite digging a tunnel with the head wedged into the very end of the closed burrow. Tunnels filled with eggshells, corneocyte debris and faecal pellets were also observed.     

Characterization of canine filaggrin: gene structure and protein expression in dog skin

Background – Filaggrin (FLG) is a key protein for skin barrier formation and hydration of the stratum corneum. In humans, a strong association between FLG gene mutations and atopic dermatitis has been reported. Although similar pathogenesis and clinical manifestation have been argued in canine atopic dermatitis, our understanding of canine FLG is limited. Hypothesis/Objectives – The aim of this study was to determine the structure of the canine FLG gene and to raise anti‐dog FLG antibodies, which will be useful to detect FLG protein in dog skin. Methods – The structure of the canine FLG gene was determined by analysing the publicly available canine genome DNA sequence. Polyclonal anti‐dog FLG antibodies were raised based on the canine FLG sequence analysis and used for defining the FLG expression pattern in dog skin by western blotting and immunohistochemistry. Results – Genomic DNA sequence analysis revealed that canine FLG contained four units of repeated sequences corresponding to FLG monomer protein. Western blots probed with anti‐dog FLG monomer detected two bands at 59 and 54 kDa, which were estimated sizes. The results of immunohistochemistry showed that canine FLG was expressed in the stratum granulosum of the epidermis as a granular staining pattern in the cytoplasmic region. Conclusions and clinical importance – This study revealed the unique gene structure of canine FLG that results in production of FLG monomers larger than those of humans or mice. The anti‐dog FLG antibodies raised in this study identified FLG in dog skin. These antibodies will enable us to screen FLG‐deficient dogs with canine atopic dermatitis or ichthyosis.     

Leporacarus gibbus and Spilopsyllus cuniculi infestation in a pet rabbit

A one-year-old male, chequered giant rabbit had a simultaneous infestation with both Leporacarus gibbus and Spilopsyllus cuniculi. Recurrent episodes of mild to severe pruritus had been noted over a period of two months. On clinical examination, partial alopecia and slightly erythematous skin with flea faeces was evident, although microscopic and cultural examinations of skin scrapings were negative for fungi. Parasitological examination, including adhesive tape strips of the rabbit's skin and fur, revealed L gibbus surface dwelling mites and the rabbit flea S cuniculi. The rabbit was successfully treated against both parasites with topical pyrethrin applied three times over a three-week period, and the clinical signs resolved in four weeks.