Pigmentary problems are often seen in dogs. The general approach is that they are difficult to diagnose with certainty and the use of biopsy and histopathology is more than useful.

Pigmentary abnormalities are also difficult to treat and depigmentation will often be permanent. Don’t forget to use sun protection on the affected skin when the dog is confronted with direct sunlight (UV).

If we have an increase in pigment in skin and hair, we talk about hyperpigmentation. If there is only excessive pigment in skin, it is called melanoderma and if it just affects hairs, we call it melanotrichia.

Genetic causes of hyperpigmentation

Lentigo. The etiology of lentigo is unknown, although papillomavirus infection has been postulated in dogs. There is no breed or sex predisposition but it is generally seen in middle aged to old dogs (1-4 years of age). Lesions appear as macular or patchy areas of hyperpigmented skin, usually on the ventrum and chest, but can spread. Lentiginosis profusa is a hereditary form of lentigo seen in Pugs and Miniature Schnauzers. No treatment is necessary as this is a cosmetic defect.

Acquired causes of hyperpigmentation

1. Post-inflammatory hyperpigmentation
   In dogs, different reaction patterns are recognised. We can see a lattice-like appearance seen with infection (bacterial or fungal as pyoderma, dermatophytosis or hypersensitivity) and chronic allergy. It can appear as a comedone formation producing blue/grey patches of hyperpigmentation in demodicosis and hyperadrenocorticism or it is a diffuse hyperpigmentation that can be seen in endocrine disease as hypothyroidism, Sertoli cell tumour and hyperadrenocorticism (Cushing’s syndrome). The underlying cause should be treated and prognosis is good.
2. Acanthosis nigricans.
   Primary idiopathic form is seen in Dachshunds. Hyperpigmentation will be seen bilaterly in the axilla. Secundary acanthosis nigricans can be seen in any breed associated with allergy, chronic pruritis and endocrinopathy leading to pigment change, especially in hypothyroidism. It presents with signs on the ventrum plus signs as pedal pruritis and otitis externa in case of atopy or bilateral flank alopecia in hypothyroidism.
   Treatment must be topical (antibacterial - antiyeast shampoo, glucocorticoid cream, antiseborrheic shampoo) and systemic (melatonin, prednisolone and vitamin E po).
3. Tumour hypermelanosis (melanoma, basal cell tumour, mastocytosis - urticaria pigmentosa -, epidermal nevi).
4. Melanotrichia.
   It has been associated with healing of deep inflammatory lesions (vasculitis, panniculitis) and resolution of endocrine or metabolic disease (hyperadrenocorticism).

A decrease in pigmentation in skin and hair is called hypopigmentation; when it only affects skin, it is called leukoderma; a lack of pigment in hair is called leukotrichia.

Genetic causes of hypopigmentation

1. Vitiligo. It is uncommon in dogs with no sex predilection but mainly seen in young dogs. Predisposed breeds include Belgian Shepherd Dogs Tervuerens, German Shepherd Dogs, Collies, Rottweilers, Dobermanns and Giant Schnauzers. It has been found especially on nose, lips, buccal mucosa, facial skin and footpads and depigmentation may be temporary or permanent. Therapy is unsuccessful and some animals occasionally will completely repigment without therapy. However depigmented skin may need sun protection.
2. Waardenburg-Klein syndrome (WKS). It occurs in young animals and there is no sex predisposition. Overrepresented breeds include Bull Terriers, Sealyham Terriers, Collies and Dalmatians. It can be seen as lack of pigment in the hair and skin (white animals) and other lesions as deafness and blue or heterochromia of irides. No therapy is available and affected animals should not be used for breeding.
3. Nasal depigmentation – Dudley nose. There is no sex predilection and mostly young dogs are affected. Predisposed breeds include yellow Afghan Hound, Samoyed, Siberian Husky, Alaskan Malamute, Labrador Retriever, white German Shepherd Dog, Golden Retriever, Poodle, Dobermann, Irish Setter and Pointer. Pigment on the nose fades from black to chocolate brown/white from puppyhood. Sudden onset depigmentation of the skin in older animals can be an early sign of epitheliotropic lymphoma. Some animals will recover spontaneously and no treatment is known or successful. However it is considered as a defect in show dogs.
4. Canine cyclic haematopoiesis. Grey Collies are predisposed with possible recurrent gastrointestinal and skin infections. Therapy with antibiotic – bactericidal drugs.
5. Albinism. Very rare in dogs.
6. Uveo-dermatologic syndrome / Vogt – Koyanagi-Harada-like Syndrome (VKH). The cause is unknown and Akita is a high predisposed breed. Commonly affected breeds are Samoyed, Siberian Husky, Alaskan Malamute, Shiba Inu, Chow Chow, Irish Setter, Dachshund, Fox Terrier, Shetland Sheepdog, St Bernard, Fila Brasiliero and OId English Sheepdog. Non cutaneous symptons are: anterior uveitis, reduced or absent papillary light reflex, conjunctivitis, ocular discharge, glaucoma, cataract, blindness and blepharospasm. Depigmentation, erythema and erosions may occur in the oral cavity. Cutaneous lesions are presented as depigmentation of nose, lips and eyelids. Occasionally also footpads, palate, scrotum, vulva and anus are affected. In some dogs, generalised depigmentation of hair can occur. Initial onset of lesions has been noted in animals ranging from 13 months to six years of age. Uveitis needs to be treated with topical or subconjunctival glucocorticoids. Glucocorticoids alone or in combination with azathioprine, oxytetracycline, niacinamide, cyclosporine or cyclophosphamide during minimal 4-8 weeks is the treatment when cutaneous lesions are diagnosed. Prognosis is guarded to fair and lifelong therapy is usually needed.

Acquired causes of hypopigmentation

1. Trauma
2. Burns
3. Infection – fungal, bacterial
4. Drugs, especially glucocorticoids
5. Copper deficiency
6. Neoplasia: epitheliotropic lymphoma and squamous cell carcinoma
7. Immune mediated disease as lupus erythematosus, VKH, pemphigus foliaceus and Leishmaniasis

In general, skin and coat health can be helped with supplementation of a complete formulation containing all essential vitamins, minerals, amino-acids and fatty acids. To obtain the best absorption and efficacy of those nutrients, a complete liquid formulation such as Viyo Elite is the best guarantee.

Dr Wim Van Kerkhoven, Viyo International nv