Vitiligo in dogs : A Rottweiler case

“Ruger” is an 8-month-old male intact Rottweiler who presented for asymptomatic, progressively worsening leukotrichia and leukoderma over the past several months.

Carine Laporte, VMD, DACVD

Dermatology for Animals, Salt Lake City

January 2025

History

Ruger developed progressive leukotrichia (whitening of the hair coat) and leukoderma (whitening of the skin) over the past several months, with no other clinical signs. Treatments had not been attempted.

Exam

Physical examination:

All vital parameters within normal limits

Bright, alert, and responsive

Dermatologic examination:

Generalized (particularly head and face) abnormal depigmentation of the hair coat, skin, paw pads, and mucocutaneous junctions (particularly nasal planum, eyelid margins, and perioral skin), with no other cutaneous abnormalities.

Ophthalmologic examination by a veterinary ophthalmologist:

No abnormalities.

Differential Diagnoses

Primary differential diagnoses were vitiligo, uveodermatologic syndrome, and premature greying.

Diagnostics

Histopathology was recommended obtain definitive diagnosis but was declined.

Figure 1. Leukotrichia and leukoderma in a rottweiler puppy.

Assessment

Vitiligo suspected

Treatment Plan

Specific treatment for vitiligo was not pursued.

The probable progression of clinical signs was discussed with the owner, with an emphasis on the fact that the loss of pigment should otherwise be asymptomatic. The development of any other clinical signs, particularly ocular disease, should prompt immediate evaluation.

Prevention of sun damage to the skin was discussed, as depigmented skin may be more likely to be affected:

• Diligent application of a canine-specific sunscreen SPF 50 or above to sparsely haired regions, repeated every 90 minutes during sun exposure
• Reduction of exposure to intense sunlight as much as able (particularly during the hours of 10 am to 4 pm)
• UV light-blocking clothing in areas not amenable to sunscreen application

 

Discussion

Vitiligo is an acquired, depigmenting skin disease characterized by a whitening of the hair and skin. In animals, it is purely a cosmetic disorder, with no systemic involvement. It is a disease that may affect many animal species, including dogs, and it also affects humans. Prevalence is poorly established in animals, likely because animals may not be brought to the veterinarian for the disease since it is not accompanied by clinical signs.

The pathogenesis of vitiligo in animals is unknown. What is known is that the ultimate outcome is the loss of melanocytes from the skin. The main hypotheses for how this occurs are based on the human variant of the disease, which may or may not reflect true pathogenesis in animals. These proposed pathogeneses are:

• Autoimmune pathways: autoantibodies directed against melanocytes have been demonstrated in humans and animals; the innate immune system (natural killer cells and inflammatory dendritic cells) and cytotoxic CD8 T-lymphocytes may also be involved
• Biochemical pathways: may include adhesion defects, oxidative abnormalities, reduced antioxidant defenses, and aberrant melanocyte-keratinocyte intercellular communication
• Neural pathways
• Genetic susceptibility
• Mechanical stress and associated trauma-induced lesions
• Microbial dysbiosis
• A combination of the above

One proposed theory is that oxidative cellular stress injures melanocytes, induces novel autoantigens, and exposes cryptic cellular antigens, which then further activates the immune system to launch an attack on the melanocytes. Additional factors (genetic, environmental, etc.) impact the individual animal’s oxidative injury and immune system response, resulting in a multifactorial disease.

In dogs, rottweilers, Doberman pinschers, and collies are predisposed. However, other breeds may also be affected. Reported ages of onset range from 2 months to 11 years old. Lesions typically begin as leukotrichia (loss of hair pigmentation) and leukoderma (loss of skin pigmentation) in macules or patches on the face (including gingiva and lips). This commonly progresses to multifocal or complete oral and facial depigmentation. Lesions in most dogs remain restricted to the face and head, but dogs may also develop depigmentation of the paw pads, scrotum, claws, paws/limbs, and neck/trunk. Lesions may be bilaterally symmetrical, multifocal, generalized, or (rarely) affect only black hair. A form of so-called follicular vitiligo involves only leukogrichia without leukoderma. Concurrent systemic illness (e.g., endocrinopathy) may be seen but is not a consistent feature of the disease.

Many dogs can be diagnosed clinically. The major findings are depigmentation without any change in epidermal architecture. Ulcers, erosions, crusts, and alopecia are not typical features of the disease.

However, if biopsy is not pursued, consideration of ophthalmic evaluation should be strongly made. The primary differential diagnosis in many cases is uveodermatologic syndrome, for which a sequela can be irreversible blindness. Most (but not all) cases of uveodermatologic syndrome involve ophthalmic lesions that develop before or concurrently with skin lesions; therefore, the lack of ocular signs consistent with uveodermatologic syndrome would further provide support for the diagnosis of vitiligo.

For more definitive diagnosis, skin biopsy would be indicated. The key histopathologic feature of vitiligo is the loss of melanocytes from the epidermis and/or hair follicle. The epidermal architecture is normal but lacks pigment granules (melanosomes), and these melanosomes sometimes spill abnormally into the dermis (pigmentary incontinence) or into the hair follicle area around the hair bulb. There may be lymphocytes associated with cell-mediated destruction of the melanocytes, but inflammation is usually minimal or absent.

Most cases of vitiligo are progressive, though spontaneous remission has been reported. Benign neglect is an option that should be discussed with owners, balancing the risks of adverse effects of any treatment with the fact that this is a cosmetic disease.

Different treatment options have been evaluated in dogs with variable success. These include ammoidin (xanthotoxin) with solar exposure, systemic glucocorticoids, adrenocorticotrophic hormone (ACTH) injections, psoralens with ultraviolet light, doxycycline-niacinamide, thyroid supplementation, L-phenylalanine, vitamin and mineral supplementation, and diet change. Psoralens and ultraviolet light, ammoidin, and solar exposure led to complete or almost complete repigmentation in small-scale canine studies.

One publication suggested that, in cases where owners strongly desire treatment, the application of glucocorticoids of high potency (e.g., 0.1% betamethasone or 0.05% clobetasol) may be applied to affected skin. Since topical glucocorticoids may result in telangiectasia, thinning of the skin, comedones, and localized skin infections, the frequency should be reduced when possible to the lowest effective. Topical calcineurin inhibitors (e.g., tacrolimus) may be an alternative to glucocorticoids. This paper suggested to avoid systemic glucocorticoids or calcineurin inhibitors (e.g., cyclosporine) because the nature of a cosmetic disease does not typically warrant the risks of adverse effects of these systemic drugs. However, systemic L-phenylalanine supplementation for 6 months may be helpful if further treatment is desired. The use of oral JAK (Janus Kinase) inhibitors has been evaluated in humans but is not yet established in animals.

 

Key Takeaways:

2. Differential Diagnoses: One of the primary differential diagnoses for vitiligo is uveodermatologic syndrome, which is an autoimmune disease with permanent and debilitating ocular sequelae. Because of this, if there is any doubt about diagnosis, eye examination and skin biopsy with histopathology are important.
3. Diagnosis: Diagnosis based on clinical appearance is appropriate if there are no signs other than loss of skin and hair pigmentation. However, histopathology can provide a more definitive diagnosis.
4. Therapy:Vitiligo is often best treated with benign neglect. Treatment options are not well established but effective options may include topical anti-inflammatories (tacrolimus, glucocorticoids), phototherapy, and L-phenylalanine. Responses may be partial, and spontaneous remission may occur.

References

1. Tham HL et al. Autoimmune diseases affected skin melanocytes in dogs, cats, and horses: vitiligo and the uveodermatological syndrome: a comprehensive review. BMC Vet Res 209; Jul 19;15:251.