Follicular dysplasia and hair loss in white-tailed deer (Odocoileus virginianus).

There have been unpublished reports of a follicular dysplastic syndrome in adult white-tailed deer (Odocoileus virginianus; WTD), known colloquially as "toothpaste hair disease." The current report aims to describe the gross and histologic lesions in skin samples from 2 adult WTDs that presented to the Wisconsin Department of Natural Resources and the Wisconsin Veterinary Diagnostic Laboratory with reports of hair loss in 2018. Both cases were grossly alopecic with sparing of the distal extremities and variably the head and neck. Histologic features included hair follicles and adnexa present in relatively normal numbers, dilated and misshapen follicles, and dysplastic hair bulbs. Hair follicles were empty, contained fragmented and irregular hair shafts, or contained concretions of keratin. Hair bulbs were rarely infiltrated by small lymphocytes, suggestive of alopecia areata as a cause of the gross appearance. This condition does not appear to be directly responsible for WTD mortality but presumably would predispose affected animals to greater environmental exposure. Evaluation of additional affected individuals is warranted to further evaluate for features of alopecia areata.

Transient chemotherapy-induced alopecia after successful reversal of 5-fluorouracil myelosuppression and neurotoxicosis in a 9-month-old dog.

BACKGROUND: 5-Fluorouracil (5-FU) cream is a common human topical chemotherapy agent with potentially fatal neurotoxic effects on dogs if accidentally ingested. There are seldom reports in veterinary literature describing the successful outcome of intervention after accidental ingestion of 5-FU cream. CASE SUMMARY: A 9-month-old spayed female labradoodle presented 14 h after ingesting an unknown amount of 40 g tube of Efudex cream (5% 5-FU). The dog presented in status epilepticus, which was managed with benzodiazepines and levetiracetam in conjunction with induced coma and mechanical ventilation. No further seizure activity occurred throughout the ensuing 5 days of hospitalisation; however, myelosuppression was featured. The dog was discharged home after 5 days of hospitalisation. Three days post discharge, the dog was noted to develop focal alopecia around the eyes and temporal region. 14 days after discharge, the alopecia progressed to a majority of the head and body. CONCLUSION: To the authors' knowledge, this is the first report that documents the enduring adverse effects of 5-FU cream after survival of the initial episode, including an earlier onset of myelosuppression and diffuse alopecia. Successful treatment of accidental 5-FU ingestion is possible several hours after the initial event with minimal long-term consequences.

Alopecias in humans: biology, pathomechanisms and emerging therapies.

BACKGROUND: The hair follicle is a complete mini-organ with a complex biology. Recent discoveries have shed light on the pathogenesis and genetic basis of a number of hair loss conditions, offering novel treatment alternatives. OBJECTIVE: To explore the biology and physiology of hair growth, the pathomechanism behind alopecias and emerging therapies. CONCLUSION AND CLINICAL IMPORTANCE: Hair growth is influenced by numerous physiological moderators. Greater understanding of the biology and physiology of the hair follicle and the pathomechanisms of hair disease facilitates development of targeted treatments. Sublingual minoxidil is a promising therapy in humans where optimised drug delivery enhances efficacy and reduces systemic adverse effects. Janice kinase inhibitors, which disrupt the inflammatory cascade, help maintain the hair follicle, preserve immune privilege, and regrow hair in alopecia areata. As the pathomechanisms of other forms of alopecia become better understood, new targeted therapies with greater efficacy will emerge.

Idiopathic seasonal alopecia in horse: case report / Alopecia sazonal idiopática em equino: relato de caso

This report describes the first case of idiopathic seasonal alopecia in a horse in Brazil. The disease is of unknown etiology, characterized by alopecic processes in the thoracic and lateral abdominal regions, in a bilaterally symmetrical way. An eight-year-old male grade horse was treated presenting hair loss in a bilaterally symmetrical manner in the arm and abdomen areas, without any other associated clinical signs. The areas with alopecia showed no pruritus, inflammation or scaling. On the epidermis, the histological evaluation presented irregular hyperplasia, hyperpigmentation, compact orthokeratosis, edema and an inflammatory infiltrate. The hair follicles were active and containing hair shaft. The case was monitored with photographic records for two consecutive years (2012 to 2014), in which the hair fall occurred at the end of autumn with spontaneous hair growth in the middle of the summer. The diagnosis was based on the history, histopathology and photographic follow-up performed. Although mentioned in the literature, this is the first clinical and pathological description of such disorder affecting an equine in Brazil.(AU)

Relata-se o primeiro caso de alopecia sazonal idiopática em um equino no Brasil, doença de etiologia desconhecida, caracterizada por processos alopécicos, nas regiões torácicas e abdominais laterais, de forma simétrica bilateralmente. Um equino mestiço, macho, de oito anos de idade, foi atendido sob queixa de perda dos pelos em regiões do tórax e do abdômen, simétrica bilateralmente, sem qualquer outro sinal clínico associado. As regiões alopécicas não apresentavam prurido, inflamação nem descamação. A avaliação histológica revelou, na epiderme, hiperplasia irregular, hiperpigmentação e ortoqueratose compacta, edema e infiltrado inflamatório. Os folículos pilosos estavam ativos e contendo hastes de pelos. O caso foi acompanhado com registros fotográficos durante dois anos consecutivos (2012 a 2014), com a queda do pelo acontecendo no final do outono e com retorno espontâneo em meados do verão. O diagnóstico baseou-se no histórico, na histopatologia e no acompanhamento fotográfico. Mesmo sendo mencionada na literatura, esta é a primeira descrição clínico-patológica de tal distúrbio acometendo um equino no Brasil.(AU)

Seasonal leukotrichia in a German shepherd dog. A case report. / Saisonale Leukotrichie bei einem Deutschen Schäferhund. Ein Fallbericht.

Leukotrichia can be caused by a variety of metabolic and inflammatory diseases. Canine alopecia areata is a rare multifactorial benign non-scarring alopecia. This case report describes a seasonally recurrent leukotrichia associated with alopecia areata in a German shepherd dog. Important differential diagnoses were ruled out and histopathology finally confirmed the diagnosis of alopecia areata. Topical tacrolimus and hydrocortisone aceponate were ineffective. The cause for the seasonal character in this case remained undetermined.

Effects of cervical headgear appliance: a systematic review

OBJECTIVE: Although much has been investigated about the effects of cervical headgear, there remains some controversy. Therefore, the objective of this systematic review is to disclose the actual effects of the cervical headgear appliance, based on articles of relevant quality.METHODS: A literature review was conducted using PubMed, Web of Science, Embase, Scopus and Cochrane databases. Inclusion criteria consisted of human studies written in English; published between 1970 and 2014; in which only the cervical headgear was used to correct Class II malocclusion; prospective or retrospective; with a clear description of cervical headgear effects; with a sample size of at least 15 individuals. No comparative studies, clinical cases or cases with dental extractions were included and the sample should be homogeneous.RESULTS: Initially, 267 articles were found. A total of 42 articles were selected by title and had their abstracts read. Finally, 12 articles were classified as with high quality and were used in this systematic review.CONCLUSIONS: The cervical headgear appliance proved efficient to correct Class II, Division 1 malocclusion. Its effects consisted in correction of the maxillomandibular relationship by restriction of maxillary anterior displacement; distalization and extrusion of maxillary molars; and slight maxillary expansion.

OBJETIVO: embora muitos estudos investiguem os efeitos do AEB cervical, ainda há algumas controvérsias sobre os seus efeitos. Portanto, o objetivo desta revisão sistemática é divulgar os efeitos reais do aparelho extrabucal cervical, com base em artigos com qualidade.MÉTODOS: os artigos foram pesquisados por meio das bases de dados PubMed, Web of Science, Embase, Scopus e Cochrane. Os critérios de inclusão consistiram em: estudos em humanos escritos em inglês; publicados entre 1970 e 2014; apenas o AEB cervical foi utilizado para corrigir má oclusão de Classe II; prospectivos ou retrospectivos; com uma descrição clara dos efeitos do aparelho; com um tamanho de amostra de pelo menos 15 indivíduos. Estudos comparativos, relatos de caso ou casos com extrações não foram incluídos e a amostra deveria ser homogênea.RESULTADOS: inicialmente, 267 artigos foram encontrados; e 42 artigos desses foram selecionados pelo título, tendo seus resumos lidos. Por fim, 12 artigos foram classificados como de alta qualidade e foram utilizados na presente revisão sistemática.CONCLUSÕES: o aparelho extrabucal cervical foi eficiente para corrigir a má oclusão de Classe II divisão 1. Seus efeitos são correção da relação maxilomandibular, com restrição do deslocamento anterior da maxila; distalização e extrusão dos molares superiores e ligeira expansão maxilar.

Alopecia areata universalis in a dog.

BACKGROUND: Alopecia areata is a T-cell mediated autoimmune disease that occurs in humans and various other mammalian species. When the disease progresses to total alopecia it is defined as alopecia areata universalis (AAU), although this outcome has only been described in humans. HYPOTHESIS/OBJECTIVES: To describe a case of canine alopecia areata universalis and its clinical outcome after 22 months of follow-up. ANIMAL: A 9-year-old intact male cross-breed hunting dog was presented with generalized and complete noninflammatory alopecia of 12-14 months duration. METHODS: Clinical examination; histopathological and immunohistochemical examination of skin biopsies. RESULTS: There was loss of all body hair including eyelashes and vibrissae. The histopathological and immunohistochemical findings supported a diagnosis of long-standing alopecia areata. Treatment with oral ciclosporin was associated with hair regrowth but muzzle hair, most eyelashes and whiskers were still lacking after 17 months of therapy. CONCLUSIONS AND CLINICAL IMPORTANCE: To the best of the author's knowledge this is the first documented case of canine AAU. The clinical and histopathological features were consistent with a diagnosis of AAU as defined in humans. Treatment with oral ciclosporin resulted in near complete resolution of the alopecia, but after 5 months without treatment the alopecia did not relapse and spontaneous resolution cannot be ruled out.

Noninflammatory, nonpruritic alopecia of horses.

Noninflammatory, nonpruritic alopecias are uncommonly encountered in the horse. Alopecia areata, an apparently autoimmune hair follicle bulbitis produces focal, multifocal to widespread hair loss. The skin is otherwise normal. Diseases that can mimic the widespread hair loss associated with alopecia areata include telogen and anagen effluvium, seasonal alopecias, follicular dysplasias (including color dilution alopecia), various nutritional deficiencies and chemical toxicosis, and diseases that result in defective hair shafts (eg, trichorrhexis nodosa and piedra). These problems are differentiated by history, physical examination, trichography, and skin biopsy. Most are cosmetic diseases that do not have predictably effective therapies.

Equine alopecia areata: a retrospective clinical descriptive study at the University of California, Davis (1980-2011).

BACKGROUND: Alopecia areata (AA) causes hair loss due to inflammatory changes within and around hair bulbs and lower portions of the hair follicles. Documentation of AA in horses is limited to a few case reports. HYPOTHESIS/OBJECTIVES: The aim of this retrospective study was to characterize equine AA by describing patterns in age, sex, breed and lesion distribution in a series of cases. An attempt was made to characterize the long-term course of the disease by surveying owners of affected horses. ANIMALS: Computerized records from 1 January 1980 to 1 July 2011 yielded 15 horses. METHODS: Descriptive statistics were calculated for age at presentation, breed, sex, dermatological signs, season when diagnosed and any recurrence of AA. The breed and sex distribution of horses with AA was compared with the equine hospital population during the study period. RESULTS: The prevalence of AA was 0.017%. Appaloosas and quarter horses were the most commonly recorded breeds. The median age was 9 years, with an age range from 3 to 15 years. Alopecia was the primary dermatological abnormality in all horses and commonly affected the mane, tail and face. More than half of the horses presented for other medical conditions. Five of seven (71.4%) owners who returned completed surveys reported a seasonal pattern to the disease, which usually worsened in spring and summer. CONCLUSIONS AND CLINICAL IMPORTANCE: Alopecia areata is a rare disease in horses, and is typically cosmetic in nature. To the authors' knowledge, this is the first study investigating the epidemiology of equine AA.

Eficácia acaricida de uma emulsão contendo 10 por cento de óleo de nim (Azadirachta indica) no controle de Psoroptes ovis em coelhos naturalmente infestados / Miticidal efficacy of an emulsion containing 10 percent neem (Azadirachtaindica) oil for control of Psoroptes ovis in naturally infested rabbits

O objetivo do presente estudo foi avaliar a eficácia de uma emulsão contendo 10% de óleo de nim, Azadirachta indica, no controle de Psoroptes ovis em coelhos naturalmente infestados. Foram utilizados 12 coelhos separados aleatoriamente em dois grupos de seis animais cada. O grupo controle permaneceu sem tratamento, enquanto que o grupo tratado recebeu a formulação em teste, contendo 10% de Nim, borrifando ambos os condutos auditivos, uma vez ao dia, por sete dias consecutivos. Os animais foram avaliados diariamente para observação de possíveis efeitos adversos do produto. Nos dias +3, +7, +14,+21, +28 e +35 foi coletado material de todos os animais para avaliação da presença de ácaros vivos. Os coelhos do grupo controle apresentavam ácaros em ambos os condutos auditivos em todos os dias de observação. O grupo tratado apresentou eficácia de 41,7% no dia +3 e 100% a partir do dia +7 até o dia +35. O produto demonstrou ser eficaz no tratamento da sarna psoróptica em coelhos. Entretanto, todos os animais tratados apresentaram reações dermatológicas, tais como alopecia e hiperemia no local de aplicação do produto, variando de baixa a média severidade.

The objective of the present study was to evaluate the efficacy of an emulsion containing 10% of neem (Azadirachta indica) oil on the control of Psoroptes ovis in naturally infested rabbits. Twelve rabbits were randomly divided in two groups of six animals. The control group remained without treatment; while animals in the other group were treated with the 10% neem extract formulation by spraying both ears daily for seven consecutive days. The animals were evaluated daily for the presence of adverse effects. Material from ears all animals was collected on days +3, +7, +14, +21, +28 and +35, and evaluated for the presence of living mites. Animals from control group presented mites in both ears along all days of observation. The treated group presented an efficacy of 41.7% on day +3 and 100% from day +7 to +35. The product containing 10% neem oil has demonstrated to be effective for the treatment of psoroptic mange on rabbits. However, treated animals presented dermatological reaction such as alopecia and hyperemia at the site of application, varying from low to medium severity.

Dermatite alérgica sazonal em ovinos deslanados no nordeste do Brasil / Sazonal allergic dermatitis in hair sheep from northeastern Brazil

Dermatite alérgica sazonal foi diagnosticada em um rebanho de 40 ovinos da raça Santa Inês no município de Jucurutú, Estado de Rio Grande do Norte. Para o estudo epidemiológico e observação dos sinais clínicos a propriedade foi visitada periodicamente entre 2007 e 2010. Os ovinos eram criados extensivamente em campo nativo cortado pelo rio Piranhas e com um açude permanente. Entre 2007 e 2009 adoeceram 13 (32,5%) ovinos de um total de 40. As lesões eram observadas durante a época da chuva e regrediam total ou parcialmente durante a seca, reaparecendo no próximo período chuvoso. Os animais que foram retirados da área se recuperaram. No final de 2009 foram eliminados os animais susceptíveis e três novos casos apareceram em 2010. A pele apresentava lesões alopécicas, crostosas, enrugadas, esbranquiçadas e com intenso prurido, localizados na região da cabeça (orelhas, ao redor dos olhos e região frontal), região dorsal do corpo e garupa. Histologicamente, a epiderme apresentou hiperqueratose, acantose, hipergranulose e moderada espongiose. Na derme havia infiltrado inflamatório, principalmente perivascular, composto por eosinófilos, macrófagos e plasmócitos. Observou-se queratose de folículos pilosos e dilatação das glândulas sudoríparas. No hemograma, os valores de todos os animais estavam dentro dos valores normais. Em abril e junho de 2010 foram realizadas capturas de insetos com armadilhas luminosas CDC, sendo 110 dípteros capturados, dos quais 43 foram identificados como Culicoides insignis Lutz. Considerando que esta espécie tem sido associada à dermatite alérgica em outras regiões conclui-se que a doença é uma dermatite alérgica sazonal associada à picada de C. insignis.

Seasonal allergic dermatitis is reported in a flock of 40 hair sheep of the Santa Inês breed, in the county of Jucurutú, State of Rio Grande do Norte, in the semiarid region of Northeastern Brazil. For the epidemiologic and clinical observations the farm was visited periodically from 2007 to 2010. The flock was raised extensively in a Paddock crossed by the Piranhas river, and had also a permanent pond. Between 2007 and 2009, 13 (32.5%) sheep out of 40 were affected. The lesions were observed during the raining season, regressed total or partially during the dry season, and reappeared in the next raining period. Sheep removed to other region recovered. At the end of 2009, all affected sheep were removed from the flock. Three new cases appeared in 2010. The skin of the affected sheep was whitish, irregularly thickened, with alopecia, crusts, and intense pruritus. Those lesions were localized more frequently in the head (ears and periocular and frontal regions) but in some animals the dorsum and croup were also affected. Histologic lesions of the epidermis were hyperkeratosis, acanthosis, hypergranulosis, and moderate spongiosis. The dermis showed infiltration by eosinophils, macrophages and plasma cells, mainly perivascular. The hair follicles showed keratosis and the sudoriparous glands were dilated. No changes were observed in the differential blood count. In April and June 2010 insects were captured by the use of CDC light trap. Forty three out of 110 dipterous captured were identified as Culicoides insignis Lutz. It is concluded that the disease is a seasonal allergic dermatitis associated with C. insignis bites.

Alopecia areata in two black Angus cows.

Adult onset progressive alopecia and leukotrichia developed in 2 registered black Angus cows, aged 6 and 7 years. Histopathologic findings in skin were prominent melanin clumping and degeneration of matrix cells with formation of giant multinucleate cells within hair bulbs, accompanied by peribulbar melanin incontinence and fibrosis and dystrophic hair shafts. Intrabulbar and peribulbar lymphocytes were cluster of differentiation (CD)3-positive T cells. Findings were characteristic of alopecia areata.

Alopecia areata and humpy-back syndrome in suckling piglets.

This report describes an uncommon variant of humpy-back syndrome associated with multiple rib fractures and multisystemic vasculitis in several nursing piglets and, for the first time, a skin disease in swine consistent with alopecia areata. Both conditions were observed concurrently on the farm and occasionally in the same piglets.

RésuméAlopécie areata et syndrome du porc bossu chez des porcelets à la mamelle. Les auteurs rapportent chez plusieurs porcelets sous la mère une variante peu fréquente du syndrome de lordose et xyphose associée à des fractures costales multiples et à une vasculite multisystémique et, pour la première fois chez le porc, une maladie cutanée compatible avec l'alopécie areata. Les 2 conditions ont été observées simultanément sur la ferme et même chez certains porcelets.(Traduit par les auteurs).

Severe bilaterally symmetrical alopecia in a horse.

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(+) 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.

Alopecia areata in Eringer cows.

Alopecia areata is a hair loss disorder in humans, dogs and horses with a suspected autoimmune aetiology targeting anagen hair follicles. Alopecia areata is only sporadically reported in cows. Recently, we observed several cases of suspected alopecia areata in Eringer cows. The aim of this study was to confirm the presumptive diagnosis of alopecia areata and to define the clinical phenotype and histopathological patterns, including characterization of the infiltrating inflammatory cells. Twenty Eringer cows with alopecia and 11 Eringer cows without skin problems were included in this study. Affected cows had either generalized or multifocal alopecia or hypotrichosis. The tail, forehead and distal extremities were usually spared. Punch biopsies were obtained from the centre and margin of alopecic lesions and normal haired skin. Histological examination revealed several alterations in anagen hair bulbs. These included peri- and intrabulbar lymphocytic infiltration, peribulbar fibrosis, degenerate matrix cells with clumped melanosomes and pigmentary incontinence. Mild lymphocytic infiltrative mural folliculitis was seen in the inferior segment and isthmus of the hair follicles. Hair shafts were often unpigmented and dysplastic. The large majority of infiltrating lymphocytes were CD3(+) T cells, whereas only occasional CD20(+) lymphocytes were present in the peribulbar infiltrate. Our findings confirm the diagnosis of T-cell-mediated alopecia areata in these cows. Alopecia areata appears to occur with increased frequency in the Eringer breed, but distinct predisposing factors could not be identified.

Alopecia areata in a rhesus monkey (Macaca mulatta).

BACKGROUND: A 14-year-old female rhesus monkey (Macaca mulatta) of Chinese origin has been suffering from alopecia universalis since childhood. METHODS: Recently, the health status of the animal was recorded comprehensively by detailed clinical examination including hematology and serology supplemented by histological and immunohistochemical investigations of skin biopsies and molecular biological techniques to clarify the causes of the persistent hair loss. RESULTS AND CONCLUSIONS: The hairless gene (hr) nonsense mutation was ruled out by polymerase chain reaction and by sequencing of the corresponding gene. Histological examinations revealed a prominent chronic lymphocytic perifolliculitis and folliculitis affecting anagen stage hair follicles as well as miniaturized hair follicles. Immunohistochemistry using the antibodies CD3, CD20 and CD4 confirmed the diagnosis of a T-cell-mediated autoimmune disease resembling alopecia areata universalis in humans.

Alopecia areata with lymphocytic mural folliculitis affecting the isthmus in a thoroughbred mare.

A 13-year-old, thoroughbred mare was presented with an 8-year history of multifocal, generalized, noninflammatory alopecia and a 3-month history of alopecia, erythema and scaling of the white star on the forehead and muzzle. Histopathological examination of biopsy samples from multiple sites on the body (mane, neck, shoulder, flank and gluteal region) showed a subtle lymphocytic inflammatory infiltrate affecting and surrounding the anagen hair bulbs, consistent with a diagnosis of alopecia areata. The biopsy sample from the star on the forehead showed atrophic hair follicles with perifollicular and mural mononuclear folliculitis affecting the isthmus. Immunohistochemical staining with a CD3 marker confirmed the T-lymphocytic origin of the inflammatory infiltrate in all the samples. The concurrent presence of lymphocytic infiltration at the bulbar and isthmic level of the hair follicles in the same horse is unusual. This finding may represent a variation of the histological appearance of alopecia areata.

A natural canine homologue of alopecia areata in humans.

BACKGROUND: Alopecia areata (AA) is suspected to be an autoimmune disease directed preferentially against hair follicles (HF) affecting both humans and various mammalian species. Recently, two rodent models of AA were described, namely the ageing C3H/HeJ mouse and the DEBR rat. Despite several case reports of canine AA in the literature, there has been no systematic assessment of the disease in these companion animals, and it is also not known whether dogs with AA could be useful as an outbred homologue of this disease in humans. OBJECTIVES: To evaluate the clinical, histopathological and immunopathological features of 25 dogs with AA and compare these data with those found in the human disease. PATIENTS/METHODS: Twenty-five client-owned dogs exhibiting macroscopic alopecia with peri- or intrabulbar lymphocytic infiltrates were selected for study. Biopsies and sera were obtained and assessed by histopathology, direct immunofluorescence of immunoreactant deposition, immunohistochemistry for lymphocyte markers, indirect immunofluorescence and immunoblotting analysis of circulating serum IgG, selective immunoprecipitation of HF proteins by serum IgG, and passive transfer of purified canine IgG into naïve C57BL/10 mice. RESULTS: Clinical signs including alopecia, skin hyperpigmentation and leucotrichia usually developed during adulthood and were first seen on the face, followed by the forehead, ears and legs. Spontaneous remission of alopecia occurred in 60% of dogs and regrowing hair shafts were often non-pigmented. Histological examination of skin biopsy specimens revealed peri- and intrabulbar mononuclear cell infiltrates affecting almost exclusively anagen HF. Direct immunofluorescence analysis detected HF-specific IgG in 73% of dogs, while indirect immunofluorescence revealed circulating IgG autoantibodies to the HF inner and outer root sheaths, matrix and precortex. Immunoblotting analysis revealed IgG reactivity to proteins in the 45-60 kDa molecular weight range and with a 200-220 kDa doublet. The latter was identified as trichohyalin by selective immunoprecipitation. Purified HF-reactive IgG, pooled from AA-affected dogs, was injected intradermally to the anagen skin of naïve mice where it was associated with the local retention of HFs in an extended telogen phase in AA-treated skin compared with that seen in controls. CONCLUSIONS: These findings are very similar to those reported for human AA patients; therefore, they support the consideration of dogs with AA as a useful homologue for the study of the pathogenesis of this common autoimmune disease of humans.