Colour dilution alopecia

23 Colour dilution alopecia




INITIAL PRESENTATION


Progressive alopecia.



INTRODUCTION


Colour dilution alopecia is a developmental disorder resulting in the weakening of hair shafts and progressive alopecia due to abnormal melanin pigment distribution within hair shafts, and within epidermal and follicular keratinocytes. It is a common condition in dogs with blue or fawn dilute colour hair coats. This case report describes a case of colour dilution alopecia in a collie with a blue hair coat.




CASE PRESENTING SIGNS


A 13-month-old, entire male Border collie was presented with a history of progressive alopecia.



CASE HISTORY


The onset of symptoms in colour dilution alopecia is usually between 6 months and 3 years of age and may present initially as gradual onset dorsal alopecia or as dorsal folliculitis. Only hairs in the dilute coat colour area are involved. When dogs present with folliculitis, there is a gradual progression of alopecia following each episode of folliculitis. Unless there is pyoderma, this is a non-pruritic disease and there is no systemic involvement. The history in this case was as follows:


• The dog had always had a dilute, blue-coloured hair coat.

• Over the past 6 weeks, there had been a progressive alopecia affecting predominantly the trunk and pinnae. White areas of hair coat were unaffected.

• There had been no evidence of pruritus and no other skin lesions.

• There were no signs suggestive of systemic involvement.

• There were no other in-contact animals.

• There was no evidence of zoonosis.

• Diet consisted of a relatively poor quality complete dried food with occasional scraps, dog chews and dog biscuits.

• The dog was regularly wormed and received routine vaccinations as a puppy.

• Flea control consisted of applications of a fipronil spot-on every 2 months.

• There had been no evidence of hair regrowth in response to 3 weeks of systemic antibacterial therapy using clindamycin at a dosage of 10 mg/kg q24 h.


CLINICAL EXAMINATION


General physical examination was unremarkable.


Examination of the skin revealed generalized, partial to complete alopecia over the pinnae and trunk (Figs 23.1 and 23.2). White areas were unaffected.


image

Figure 23.1 Initial presentation. Generalized partial alopecia over the trunk.


image

Figure 23.2 Initial presentation. Pinnal alopecia.


There was loss of primary hair shafts over the pigmented areas, revealing a blue to brown, dilute coloured undercoat.




DIFFERENTIAL DIAGNOSES


In this case, the history and clinical signs were strongly suggestive of colour dilution alopecia, although other causes of non-pruritic alopecia were potential rule-outs. The involvement of a staphylococcal folliculitis could be ruled out on the basis of no response to the previous antibacterial therapy. In tardive onset cases, causes of hair follicle arrest, such as hypothyroidism and hyperadrenocorticism, should also be considered as differentials.


Therefore, the differential diagnosis list was:


• Colour dilution alopecia

• Other causes of follicular dysplasia

• Pattern alopecia

• Demodicosis

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Sep 3, 2016 | Posted by in SMALL ANIMAL | Comments Off on Colour dilution alopecia

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