Follicular Dysplasia of the Adult Doberman Pinscher
This paper presents the case of an adult female, red Doberman pinscher affected by permanent hypotrichosis, limited to the dorsolumbar region and sides of the trunk. The hypotrichosis began at approximately the age of 2 years and progressed slowly with no skin hyperpigmentation. The clinical and histopathological characteristics are of an uncommon form of follicular dysplasia.
Introduction
Follicular dysplasia is the generic name for a group of cutaneous diseases characterized by an imperfect development of the hair follicle. Follicular dysplasia is clinically manifested by abnormal or fragile hair shafts, which may result in hypotrichosis or alopecia, the location of which varies according to the type of dysplasia and the affected breed.1–3
In 1990, Miller described a type of follicular dysplasia in four black and two red Doberman pinschers; the condition was considered to be a rare and characteristic type of genodermatosis.4 These dogs showed progressive loss of hair, which began in adulthood and slowly progressed to areas of alopecia limited to the dorsolumbar region and the flanks. At a histological level, these Doberman pinschers had orthokeratotic hyperkeratosis, follicular dilatation, peribulbar melanophages, and pigmentary alterations; however, sebaceous glands and arrector pili muscles were normal. In all six dogs, the pigmentary alterations were due to melanin aggregates in the cortex of the hair shafts; in three cases, free melanin aggregates were present in the hair follicles.
Since the Miller report was published 2 decades ago, no new cases of this dysplasia appear to have been reported. Herein, we report a case of follicular dysplasia in a Doberman pinscher that had clinical and histopathological aspects similar to those described by Miller.4
Case Report
Medical History and Clinical Findings
In August 1996, an intact female, 4-year-old, red Doberman pinscher with an unknown family history was presented for examination of a mammary nodule. No history of any health problems (except for loss of hair in the lumbar region and flanks, producing areas of hypotrichosis) was reported. The dog lived in a clean environment and was housed primarily outdoors in a geographic region (southern Brazil) with well-defined seasons. The dog was fed a high-quality commercial dog food and received all routine vaccinations on a yearly basis. No imbalance of the estrous cycle or any signs of abnormal behavior were seen, and the dog was active and had a docile nature. The loss of hair had begun at approximately 2 years of age and progressed slowly, with some episodes of scaling. During visits to other veterinarians, the possibility of a hormonal disorder had been raised; however, attempts at recognized treatments had no effect, and the owner could not provide details about these treatments.
Although excision of the mammary nodule had been recommended, the owner preferred to wait, returning 4 years later when the nodule had become an evident mass involving the two mammary chains. A mastectomy was performed in two stages, and the neoplasm was identified as cystic mammary adenocarcinoma. No complications were noted during the postoperative period.
At the time of the mastectomy, the dog was 8 years old and still had hypotrichosis; however, the affected area of the dorsolumbar and lateral trunk regions was now larger than the area originally noted 4 years previously. The hypotrichosis was accompanied by areas of alopecia and desquamation [Figures 1A, 1B]. The owner scheduled an appointment to have the dog reexamined and to have laboratory tests performed to diagnose the dog’s dermatological condition. Unfortunately, the dog was presented in the interim with a pyometra. Despite emergency surgery, the dog died 5 days later. The owner allowed us to collect dermal samples for histopathological examination postmortem.
Dermatohistopathological Findings
In the areas affected by hypotrichosis, superficial orthokeratotic hyperkeratosis and follicular keratosis were evident. Some degree of follicular inactivity in addition to a large number of dysplastic hair shafts and follicles associated with melanin aggregates and peribulbar melanophages were also noted. The arrector pili muscles were normal, as were the sebaceous glands that showed no atrophy or melanization [Figures 2A–2D]. Rare flame follicles were seen. The elastin content was evaluated by acid orcein and Giemsa staining and was considered normal when compared to the skin of normal adult Doberman pinschers.
Discussion
Although it was not possible to apply hormonal measurements to refute endocrinopathies, the clinical characteristics, evolution, and histopathological details are similar to those found by Miller4 in red Dobermans, justifying this report. Hormonal disorders such as hypothyroidism, hyperadrenocorticism, and sex hormone dermatoses can cause loss of trunk hair. The first two endocrinopathies (i.e., hypothyroidism and hyperadrenocorticism), if not duly treated, cause a more widespread distribution of hypotrichosis than follicular dysplasias, and hair loss is associated with other clinical signs that clearly indicate the presence of a systemic disease. Sex hormone dermatoses in females usually cause alopecia of not only the trunk but also the perineal and inguinal regions. In addition, abnormalities in the reproductive cycle and increased size of the vulva and mammary glands (i.e., hyperestrogenism) may be noted, or the estrous cycle may be absent or irregular, with loss of hair on the caudal region of the thighs and changes in the general quality of the hair.1,4
Other cutaneous disorders that can cause loss of hair on the trunk region are alopecia X and cyclical flank alopecia; both have unknown etiologies. Dogs affected with alopecia X have a fleecy look because of the gradual loss of primary hair and retention of the secondary hair. As well, affected dogs have areas of hypotrichosis evolving to alopecia, which generally extends to the neck, ears, tail, and caudomedial region of the thighs.1,5 The latter disease, cyclical flank alopecia, occurs in dogs residing in regions of the world where the seasons of the year are well defined. This disease generally has the prominent characteristic of seasonal hair loss and hair regrowth, which causes areas of alopecia with well-demarcated borders that usually become hyperpigmented.1,3,6,7 Histologically, cyclical flank alopecia is characterized by the presence of follicles with the appearance of a malformed foot or an octopus, with marked melanosis of the sebaceous glands and plugs of melanin in sebaceous ducts.1,3,6–8
With chronicity, all of the above dermatopathies tend to cause hyperpigmentation of the alopecia areas; such hyperpigmentation was not observed in the Doberman pinscher presented in this case.
Alopecia X and hormonal disorders such as hypothyroidism and hyperadrenocorticism cause changes to the cutaneous histology, including orthokeratotic hyperkeratosis, follicular dilatation, follicular inactivity, and atrophy of the sebaceous glands. However, accumulation of melanin aggregates in the hair shafts and follicles is not typical. In addition, dogs with hyperadrenocorticism frequently have calcinosis cutis; dogs with hypothyroidism have hypertrophy with vacuolation of the arrector pili muscles; and dogs with alopecia X have decreased elastin levels of the skin, although these are not consistent findings.1,4,8 Nonetheless, the details outlined above are those habitually used as criteria for making a distinction between follicular dysplasias and endocrine dermatosis.1,4,8
In the dog of this report, orthokeratotic hyperkeratosis, follicular dilatation, follicular inactivity, and melanin deposits were present; however, no atrophy of the sebaceous glands, calcinosis cutis, or abnormalities of the arrector pili muscles or elastin were noted.
Bagladi et al carried out a retrospective study with 107 dogs with endocrine disorders and 71 dogs with follicular dysplasias to determine whether melanosis of the sebaceous glands observed in follicular dysplasias could serve as a criterion for histopathological distinction between the two entities.9 Bagladi et al concluded that melanosis of the sebaceous glands can occur in endocrinopathies (17.8%), and as long as the melanosis is linked to the sebaceous gland atrophy, the diagnosis of an endocrine disorder is probable.9 Rothstein et al considered that a large number of dysplastic follicles along with the combination of dysplastic hair shafts, dysplastic follicles, and aggregates of melanin in the hair shaft support the diagnosis of follicular dysplasia.10
Follicular dysplasias that bear some histopathological similarity to the follicular dysplasia of black and red Doberman pinschers have been described in several breeds and their crosses. Follicular dysplasias in other breeds, however, can be distinguished by their particular histopathological features and/or by clinical aspects such as age at onset, evolution, and distribution of the hypotrichosis.11–16
From a clinical point of view, several notable characteristics of the case presented here correspond to the cases reported by Miller.4 These are the breed; the nondiluted coat color; the onset of hair loss in adulthood; the fact that the slowly progressive evolution of hypotrichosis, although permanent, did not become generalized; and the fact that the skin maintained its normal thickness and did not become hyperpigmented. From a histological viewpoint, the following corresponding findings are noteworthy: the absence of atrophy and melanization of the sebaceous glands and the presence of peribulbar melanophages, dysplastic hair shafts, and melanin aggregates in the hair and follicles. The pigmentary alterations, while similar to the illustrations in Miller’s report, were less obvious in the dog presented herein; however, Miller observed that histological pigmentary changes were less evident in red Dobermans compared to black ones.4
In 1995, Foil, taking the Freire-Maia classification of human ectodermal dysplasias as a model, created a classification of canine and feline ectodermal dysplasias in which the follicular dysplasia of black and red Doberman pinschers is considered a form of color dilution alopecia within group 1a*.17–19 Foil admitted that Doberman pinschers are heterozygotes (Dd) and not homozygotes (dd) as are dogs with diluted coats;17 however, these two dysplasias (i.e., follicular dysplasia of black and red Doberman pinschers and color dilution alopecia) have pigmentary alterations of the hair follicles in common.4 Thus, the possibility that these two conditions are clinical variants of the same pathological entity should not be refuted. Considering there was no dilution of color in the dogs studied by Miller,4 nor in the female red Doberman pinscher presented in this case (and differences are obvious in the evolution and distribution pattern of the hypotrichosis between the two dermatoses, and the pigmentary alterations are much more evident in the color dilution alopecia),3,4,20 we suggest that these two conditions should be considered different dysplasias. This case may in fact be one of locus heterogeneity (i.e., when different genes determine similar clinical conditions).
Conclusion
Follicular dysplasia of the adult Doberman pinscher should be considered in the differential diagnosis for all Doberman pinschers with adult-onset bilateral hypotrichosis on the trunk. Although this follicular dysplasia appears to be uncommon, the lack of reports and detailed studies may reflect the lack of diagnosis rather than its true frequency in dog populations.
Citation: Journal of the American Animal Hospital Association 46, 2; 10.5326/0460143
Citation: Journal of the American Animal Hospital Association 46, 2; 10.5326/0460143
(A) Dog at 8 years of age showing permanent bilateral hypotrichosis, which began at the approximate age of 2 years. The hypotrichosis progressed slowly and was limited to the dorsolumbar and lateral trunk regions. Skin was not hyperpigmented. (B) Close-up of a focus of scaling.
Histopathological features: (A) Dysplastic hair follicle and normal sebaceous glands; (B) hair bulb with melanin aggregates and peribulbar melanophages; (C) melanin deposits in the cortex of a hair shaft; (D) melanin aggregates in the hair follicle wall (secondary hair). Hematoxylin and eosin stain; bar=25 μm.
