A variety of cat breeds have been developed via novelty selection on aesthetic, dermatological traits, such as coat colors and fur types. A recently developed breed, the lykoi (a.k.a. werewolf cat), was bred from cats with a sparse hair coat with roaning, implying full color and all white hairs. The lykoi phenotype is a form of hypotrichia, presenting as a significant reduction in the average numbers of follicles per hair follicle group as compared to domestic shorthair cats, a mild to severe perifollicular to mural lymphocytic infiltration in 77% of observed hair follicle groups, and the follicles are often miniaturized, dilated, and dysplastic. Whole genome sequencing was conducted on a single lykoi cat that was a cross between two independently ascertained lineages. Comparison to the 99 Lives dataset of 194 non-lykoi cats suggested two variants in the cat homolog for Hairless (HR) (HR lysine demethylase and nuclear receptor corepressor) as candidate causal gene variants. The lykoi cat was a compound heterozygote for two loss of function variants in HR, an exon 3 c.1255_1256dupGT (chrB1:36040783), which should produce a stop codon at amino acid 420 (p.Gln420Serfs*100) and, an exon 18 c.3389insGACA (chrB1:36051555), which should produce a stop codon at amino acid position 1130 (p.Ser1130Argfs*29). Ascertainment of 14 additional cats from founder lineages from Canada, France and different areas of the USA identified four additional loss of function HR variants likely causing the highly similar phenotypic hair coat across the diverse cats. The novel variants in HR for cat hypotrichia can now be established between minor differences in the phenotypic presentations.
A 9-year-old Tennessee Walking Horse gelding was presented for diagnosis of the cause of extensive alopecia. Complete hair loss was noted over the head, neck, shoulder, thigh, and proximal limbs, but the trunk, distal limbs, pelvic area, mane, and tail were unaffected. The alopecic areas were visually noninflammatory with no exudate or crust except on the shoulder and along the back, where multifocal patchy areas of alopecia with scales and crust were evident. The horse was slightly pruritic. Microscopically, the hair bulbs, inner and outer root sheaths of inferior segments, and perifollicular regions were infiltrated by small to moderate numbers of small lymphocytes. Similar inflammation was occasionally evident in isthmus follicular walls as well as some apocrine glands. No sebaceous glands were affected. Immunohistochemistry confirmed that the small lymphocytes were CD3 þ T lymphocytes. The epidermis from the skin with scale and crusts along the horse's back exhibited mild to moderate hyperplasia, mild lymphocytic exocytosis, mild eosinophilic dermatitis, and diffuse parakeratosis with numerous budding yeasts, consistent with Malassezia spp. The final disease diagnosis was made as alopecia areata with Malassezia dermatitis. Alopecia areata could be a contributing underlying factor for Malassezia dermatitis. Keywords alopecia areata, Malassezia dermatitis, immunohistochemistry, horseA 9-year-old Tennessee Walking Horse gelding was presented to the Veterinary Medical Teaching Hospital, College of Veterinary Medicine, University of Missouri, with extensive alopecia. Bilaterally symmetrical complete hair loss was noted over the head, neck, shoulder, thigh, and proximal limbs, but the trunk, distal limbs, pelvic area, mane, and tail were unaffected (Fig. 1). The alopecic areas were clinically noninflammatory with no exudate or crust except on the shoulder and along the back, especially on the right side, which were multifocally covered with scales and crust. Both pigmented and nonpigmented skin was affected to a similar extent. At the periphery of areas of alopecia, hairs were loose and easily epilated. The horse was slightly pruritic. According to the owner, the alopecia had involved only the head and neck throughout the antecedent 1.5 years, slowly progressed, and then suddenly spread to affect more extensive areas of the body during the 1 to 2 weeks prior to admission. The referring veterinarian had submitted blood for determination of iodothyronine concentrations when alopecia had first been evident 14 months earlier, at which time the circulating thyroxine concentration was very low (T4: <0.05 ug/dL [reference range: 0.5-4.0 ug/dL]; T3: 41.1 ng/dL [reference range: 30-115 ng/dL]). At that time, the gelding's physical appearance was also characterized by marked thickening of the crest of the neck. The veterinarian had addressed suspected hypothyroidism by treating the gelding using an orally administered thyroxine supplement (Thyro-L) for several weeks. At the Veterinary Medical Teaching Hospital, the ...
A 2-year-old, female spayed, domestic shorthair cat presented to the University of Missouri-Veterinary Medical Teaching Hospital (UMC-VMTH) with an approximately 11-month history of fluid-draining pockets along her ventral thorax and axillae. The skin in these regions was erythematous, and multiple areas drained a serous to serosanguinous fluid. Fluid-filled, nodules formed along the ventrum, but these nodules disappeared as fluid drained spontaneously. Histologic assessment of skin biopsies revealed areas of vascular proliferation extending along the deep margin of the section and rare instances of invasion into the superficial dermis. These vascular channels were devoid of cells, lined by variably pleomorphic endothelial cells which had a low mitotic index. Based on the mild to moderate pleomorphism, positive staining with prospero-related homeobox gene-1 (PROX-1), and the locally aggressive nature of the tumor, a final diagnosis of lymphangiosarcoma was made.
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