Alopecia in the cat: Part 2
Ewan Ferguson BVM&S DVD MRCVS
RCVS DIPLOMATE IN VETERINARY DERMATOLOGY
THE GODDARD VETERINARY GROUP, WANSTEAD, LONDON. E11 2SY/WEY REFERRALS, WOKING, SURREY. GU21 5BP
THE GODDARD VETERINARY GROUP, WIMBLEDON, LONDON. SW19 5AU
ANDERSON STURGESS VETERINARY SPECIALISTS, WINCHESTER. SO21 2LL
In the first of the articles on feline alopecia, the most autosomal recessive trait. The Sphynx or
common cause of alopecia in the cat, hair loss due to Canadian Hairless breed is the result of selective
self-trauma, was reviewed. In this, the second of the breeding for a variant of the Cornish Rex gene.
series, alopecia arising from developmental The Sphynx allele is incompletely dominant
abnormalities or failure of intrinsic or extrinsic over the Devon allele and both are recessive to
follicular control mechanisms is considered. Some of the wild type. Crossbreeding with the Devon
these conditions, such as pattern alopecia or post- Rex has led to serious dental or nervous system
inflammatory defluxion, are common, but most are problems in the past.
comparatively rare. Some are confined to a specific
breed or are associated with specific diseases.
Broadly speaking, this group of alopecias fall into
several distinct categories:
1. Congenital and hereditary alopecias
2. Alopecia associated with acquired follicular
pathology (intrinsic factors)
3. Alopecia arising from non-follicular pathology
1. CONGENITAL AND HEREDITARY ALOPECIAS
Rarely, areas of ectoderm fail to develop normally
during foetal development, which may lead to a
variety of clinical patterns affecting the follicles and
adnexae and skin.The prognosis depends entirely on
the extent and severity of the original lesion. Mild
cases may result in no more than areas of permanent
alopecia whilst more extensive lesions may heal by
secondary intention and produce extensive scarring.
The most severe cases are incompatible with survival.
Abnormalities in morphogens or structural proteins
result in hair shaft distortion or follicles that are so
Fig. 1: Devon Rex showing extensive congenital hypotrichosis. Note also the
malformed that hair growth is abnormal or marked pattern alopecia affecting the preauricular skin. This is normal in the
impossible. However, in general the follicular cycle is breed.
maintained. As most of these conditions give rise to
abnormalities in hair shaft morphology, any alopecic
disease with no apparent follicular abnormality is
probably not a follicular dystrophy.
Hair shaft abnormalities
A variety of conditions affecting the shape,
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composition and strength of the hair shaft are
recognised in the cat:
1. Extensive congenital hypotrichosis may be seen
in breeds such as the Cornish and Devon Rex
(Fig. 1), Burmese, Birman, and Siamese. In the
latter two breeds the condition is due to an
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2. Trichorrhexis nodosa - nodular mid-shaft hair alopecia may present as a transient, idiopathic
fracture, usually an acquired defect and may be condition in the Siamese.The cause is unknown and
associated with infections (Fig. 2) or the regrowth usually occurs spontaneously after several
excessive use of shampoos. Overgrooming can months.
also produce similar hair shaft lesions and it is
therefore imperative to rule out hypersensitivity 2. ALOPECIA ASSOCIATED WITH ACQUIRED
and pruritus. FOLLICULAR PATHOLOGY
Traction alopecia has been described in animals that
have had elastic bands or other devices used to tie
back the hair, usually on the head. If the device is
applied too tightly or for too long, an atrophic
alopecia may develop. Early lesions show a
mononuclear infiltrate, oedema and vasodilation
whilst chronic lesions progressively fibrose and show
Demodicosis in the cat is caused by Demodex cati, D.
Fig. 2: Trichorrhexis nodosa affecting the vibrissae of gatoi and a third, still unnamed Demodex species. D.
a Persian caused by focal bacterial infections. cati inhabits the follicle and is morphologically
similar to D. canis, although eggs and all immature
3. Pili torti - flattening, rotation and exaggerated stages are slightly slimmer. Demodicosis is a rare
curvature of the hair shaft. Usually has a condition in the cat usually presenting as patchy
hereditary basis and may show other cutaneous erythema, alopecia, scaling and crusting. Lesions are
abnormalities. May selectively affect secondary typically localised to the face, head and neck and the
hairs. Localised pili torti can arise from condition is usually self-limiting. It may occur as a
folliculitis. ceruminous otitis. Generalised demodicosis due to
4. Shaft disorder of Abyssinian cats - rare. Only the D. cati is rare and although not as severe as the canine
vibrissae and primary hairs are affected.The hairs form, many cases are associated with underlying
are rough, dull and show bulbous swellings, often disease such as diabetes mellitus, lupus erythematosus
at the tip. An inherited disorder restricted to or hyperadrenocorticism or immunocompromise
Abyssinian cats, there is no effective treatment. arising from feline leukaemia virus or feline
immunodeficiency virus infection. Purebred Siamese
Bulb matrix and melanocytes abnormalities and Burmese may be predisposed. D. gatoi inhabits
1. A form of follicular dysplasia has been reported the superficial interfollicular stratum corneum and
in the Cornish Rex associated with the presence can be associated with severe disease suggestive of
of abnormal clumped macromelanosomes scabies or hypersensitivity. Common lesions include
distorting hair shaft anatomy. This condition is scaling, excoriations, crusting, multifocal erythema
slowly progressive resulting in symmetrical and hyperpigmentation with secondary self-inflicted
truncal alopecia. alopecia. It is contagious and all in-contact animals
should be treated.
2. Cats with blue or cream coloured coats carry the
Maltese dilution gene resulting in clumping of Amitraz rinses and ivermectin have been used
melanosomes in the hair shafts and follicular successfully to treat both forms of demodicosis.A full
epithelium. However, hair shaft pathology and discussion of treatment options lies beyond the scope
dysplastic changes in the follicle are rare. of this article and more detailed information should
be sought before embarking on treatment. These
Pattern alopecia products are not licensed for use in cats; there are at
Pattern alopecia occurs as a symmetrical diffuse present no products with such a licence.
thinning of the hair coat in specific regions of the
body. One example, seen in most cats, is preauricular Dermatophytosis
pattern alopecia. Vellous transformation or Feline dermatophytosis most commonly presents as
miniaturisation of the follicles may be seen. Pinnal one or more irregular patches of alopecia.The hairs
in affected areas are broken and frayed and the skin
may show a variable degree of scaling. Follicular
hyperkeratosis gives rise to follicular plugging and
Subs hotline: 01635 254911
comedo formation. There may be minimal
inflammation whilst other cases may show areas of
folliculitis, erythema, scale, crust and follicular
papules. Recurrent folliculitis resembling feline acne or
stud tail can be seen. Widespread, pruritic, exfoliative
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erythroderma with extensive secondary self-inflicted destruction of the follicles with haemorrhage and
alopecia may be observed. Dermatophyte kerions oedema. Arthropod bites are the most common
occurs occasionally whilst dermatophytic pseudo- triggers with mosquito bite hyper-sensitivity
mycetomas have been reported only in Persians. being a good example. Rarely, cutaneous drug
reactions, feline herpes virus dermatitis and
Fungal culture is required to speciate dermatophyte ischaemia produce a cell-poor or neutrophil
infections, as this cannot reliably be inferred from the dominated necrotising mural folliculitis.
clinical lesions. G Pustular mural folliculitis describes the
formation of microabscesses and pustules within
Folliculitis the wall of the outer root sheath. Examples of
A number of distinct pathological patterns are this pattern are seen in follicular pemphigus
recognised though not all have been specifically foliaceus and pemphigus erythematosus or
described in the cat. All patterns lead to varying panepidermal pemphigus.
degrees of alopecia, often with other accompanying
clinical signs which may help the clinician 3. Luminal folliculitis
differentiate between these conditions: This is the most widely recognised histological
1. Perifolliculitis pattern of folliculitis. It is usually associated with
Describes an inflammatory reaction surrounding, but invasion of the follicle by infectious agents.
not infiltrating, the outer root sheath of the follicle Inflammatory cells, normally neutrophils, migrate
which does not cause basal cell destruction. Where into the follicular lumen before releasing their
only the follicular ostia is involved, this is more inflammatory mediators. As a result, mural destruction
properly described as a spongiotic dermatitis. starts from the inside of the follicle rather than the
Examples in the cat would include acute outside, as in the mural folliculitides. Bacterial
hypersensitivity triggered dermatitis, leishmaniasis folliculitis, dermatophytosis and demodicosis typically
and some forms of sebaceous adenitis. produce this pattern.
2. Mural folliculitis 4. Bulbitis
Occurs when the inflammatory process targets the In this pattern, a lymphocytic inflammatory pattern
wall, or outer root sheath, of the follicle and the is targeted at the inferior portion of the follicle.This
lumen is spared. Four main subdivisions are occurs in alopecia areata - since the follicular stem
recognised: cells reside higher up the follicle and are not placed
G Interface mural folliculitis is a relatively non- at risk by any mural involvement, spontaneous
specific pattern often seen with perifolliculitis. recovery usually occurs over time.
The basal cell layer may be targeted with varying
severity, resulting in hydropic change, and 3. ALOPECIA ARISING FROM NON-FOLLICULAR
keratinocyte apoptosis. Conditions where this PATHOLOGY
pattern is seen include lupus erythematosus, Hair cycle abnormalities
erythema multiforme, cutaneous adverse drug 1. Alopecias associated with systemic disease
reactions, thymoma-associated exfoliative In the dog, alopecia is a common feature of
dermatitis and various vasculitides and endocrine disease whereas in the cat, it is much less
vasculopathies, such as rabies vaccination commonly encountered. Hyperadrenocorticism
reactions where a scarring alopecia resulting occurs typically in middle-aged to older cats.
from follicular destruction and secondary fibrosis Females are more commonly affected but there is
occurs. no breed predisposition. Clinical signs include
G Infiltrative mural folliculitis occurs when there is polyuria/polydipsia, weight loss, muscle wasting, skin
infiltration of the follicle wall by lymphocytes fragility, comedone formation and seborrhoea.
and histiocytes without accompanying hydropic Medial curling of the ear tips is seen in iatrogenic
degeneration and apoptosis. A variable degree of hyperglucocorticism but has not been reported in
mural destruction may be seen. In feline naturally occurring hyperadrenocorticism. Skin
idiopathic lymphocytic mural folliculitis and changes, including alopecia, only occur in
primary sebaceous adenitis; mural damage does approximately 50% of cases. Ninety per cent of
not occur whereas in secondary sebaceous affected cats are prediabetic or overtly diabetic due
adenitis, the outer root sheath is destroyed in a to the insulin antagonistic activity of cortisol. The
number of patterns. Other conditions showing diabetes frequently becomes subclinical after
this infiltrative pattern include pseudopelade, successful management of the hyperadrenocorticism.
early epitheliotrophic lymphoma and alopecia Cats often present late in the course of the disease,
mucinosa where accompanying mucinosis of the which then carries a poorer prognosis due to the
outer root sheath is seen. advanced development of degenerative changes and
G Necrotising mural folliculitis may be considered diabetes mellitus.
as a distinct pattern of infiltrative mural
folliculitis. The inflammatory infiltrate is usually Biochemical and haematological changes are of
eosinophil-dominated and may cause explosive limited diagnostic specificity. More than 20% of cats
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do not show adrenal suppression with 0.01 mg/kg of are recognised in man but such subdivision, whilst
dexamethasone and a dose of 0.1 mg/kg is suggested perhaps applicable, has not been undertaken in
for suppression testing. All cats with hyper- animals.
adrenocorticism have failed to suppress to normal
levels (<10 µg/l). Most affected cats will show an 2. Alopecias associated with abnormalities
exaggerated response to ACTH but equivocal or localised to the follicle and surrounding tissues
normal responses can be seen. Response to medical (paracrinopathies, autocrinopathies)
treatment is variable and some clinicians suggest G Post-inflammatory alopecia
bilateral adrenalectomy as the treatment of choice. Following any episode of acute inflammation,
overlying skin frequently exhibits an abrupt,
Congenital hypothyroidism has been reported in the complete shedding of the hair coat resulting in
cat and leads to decreased growth rates, stunting, total alopecia in a well-demarcated patch
lethargy and dwarfism.The coats are full but dry and overlying the inflamed tissue. A typical example
lacking in primary hairs. Spontaneous hypothyroidism would be the hair loss seen in skin surrounding
occurs very rarely and has produced a dull dry, and overlying a cat bite abscess. The hairs are
seborrhoeic coat with poor regrowth. Cats telogenised, easily epilated and lost in large
undergoing radioablation of the thyroid glands clumps. This form of loss probably represents an
resulting in induced hypothyroidism exhibited immediate telogen release (Type 4 telogen
transient lethargy, coat matting, seborrhoea and defluxion) where normal telogen is shortened
alopecia of pressure points, pinnae and dorsal and and hair loss begins within a few days.
lateral tail base.
In chronic inflammatory dermatitis, diffuse
Cutaneous abnormalities occur in approximately alopecia may also develop. Rather than complete
30% of cats with hyperthyroidism and include alopecia, there is a progressive thinning of the
excessive shedding and focal or symmetrical alopecia coat and this again probably represents a variant
associated with overgrooming. Chronic cases may of telogen defluxion.
mimic hyperadrenocorticism with thin, hypotonic
skin and extensive truncal alopecia. G Topical ‘spot-on’ reactions
The trend towards the formulation of routine
Hyperoestrogenism and oestrogen responsive ectoparasiticides as topical ‘spot-on’ products has
dermatosis will produce alopecia in the dog but are given rise to the appearance of a novel focal
extremely rare in the cat. alopecia. This takes the form of a well-defined
focal patch of alopecia appearing at the site of
Diabetes mellitus is a common feline endocrinopathy administration within a few days of treatment. It
and may also result in changes similar to those seen may be preceded by localised pruritus or
in hyperthyroidism. Thin, hypotonic skin with irritation and mild localised crusting. It is most
variable alopecia and generalised seborrhoea are the likely to represent an adverse reaction to the
more common cutaneous signs. Xanthomatosis has vehicle used in the formulation rather than the
also been reported in both naturally occurring and active agent. The alopecia and irritation are
megestrol acetate-induced diabetes mellitus. transient but may recur on reapplication of the
same product. Substitution with a different ‘spot-
Anagen defluxion occurs when a severe insult occurs on’ formulation is indicated.
to the anagen follicles, resulting in abnormalities of the
follicle and hair shaft. As anagen progresses, hair loss Atrophic abnormalities
occurs abruptly, within days of the insult. Examples 1. Depot glucocorticoid atrophy
of triggers that can potentially induce anagen Local, well demarcated patches of alopecia associated
defluxion include therapy with anti-mitotic drugs, with pigmentary changes and dermal, epidermal and
infectious disease and exposure to a range of toxins. adnexal atrophy may be seen. The injected material
may be visible through the atrophic skin and the
Telogen defluxion occurs 4-12 weeks after an episode tissues are palpably thinner than surrounding skin.
of physiological stress such as severe illness or The changes may not be reversible. Focal alopecia
pyrexia, shock, surgery or anaesthesia. It may also has also been reported with the use of topical
occur following the removal of an abnormal glucocorticoid preparations, typically at the base of
telogenising influence such as an endocrinologically the pinna following administration of otic products.
active neoplasm, correction of a systemic
endocrinopathy such as hyperadrenocorticism or 2. Vellous transformation
withdrawal of glucocorticoid or progestagen therapy. Progressive telogenisation and miniaturisation of the
In all cases, premature cessation of the anagen phase follicle, progressing through to atrophy. Small scaled-
results in synchronisation of the follicles in catagen down hairs may be produced or the follicle may be
and then telogen. As a new wave of hairs is lost. This pattern is seen in paraneoplastic alopecia
produced, the telogen hairs are shed in synchrony. (Fig. 3) where hair is easily epilated all over the body.
Several distinct functional types of telogen defluxion The syndrome presents in older cats with a history
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of weight loss, lethargy and inappetance. The skin in the genital and perineal regions is the most
becomes characteristically smooth, shiny and alopecic. common initial presentation. This may progress to
Adnexal atrophy may be severe. A diagnosis of thinning of the coat over the lateral thorax and flanks
pancreatic neoplasia of either acinar cell or pancreatic but the dorsum is usually unaffected. Pruritus and
duct origin is usually made on exploratory skin lesions are absent.
laparotomy. The prognosis is usually grave although
early surgical intervention may be curative. Since overgrooming can produce an identical pattern,
it is essential to eliminate self-trauma as a cause. Cats
can be secretive about grooming, particularly if the
activity attracts unwelcome attention. Close
examination of plucked hairs will help identify those
animals where self-trauma is playing a role and these
will, in general, far outnumber those where acquired
symmetrical alopecia is a genuine differential.
Conflicting reports on the thyroid status of cats with
this syndrome have been published but as a group,
there appears to be a depressed TSH response.
Therapy with T3 has been recommended but
combined androgen-oestrogen therapy appears to be
more successful. Progestagens have also been used
Fig. 4: Paraneoplastic alopecia in a domestic shorthaired cat. Note the but bearing in mind the occasionally severe adverse
characteristic smooth, shiny, alopecic appearance of the skin. (Illustration courtesy effects associated with all these treatments, full
of Dr Ross Bond, RVC.)
consideration should be given to the benign, non-
life-threatening and essentially cosmetic nature of
3. Arrested follicular cycle this condition.
Some older cats develop thick, dense coats that
become dry, brittle and faded, sometimes In summary, when confronted by alopecia in the cat,
accompanied by mild diffuse scaling.This appears to it should be remembered that the vast majority of
occur because the follicular cycle becomes cases eventually prove to be self-inflicted. Only after
prolonged or arrested, remaining in telogen for an overgrooming has been definitively excluded,
extended period. Hairs are progressively damaged by whether by dietary trials or parasite control, on the
mechanical, chemical and physical insult and the basis of clinical history or biopsy or even through
melanin is gradually photodegraded, leading to therapeutic trials with antipruritics should
fading of hair shaft pigmentation. Hairs are shed but alternative differentials be considered.
not replaced and over a long period, patches of
alopecia can develop in areas subject to rubbing or
overgrooming. In the absence of any recognisable
systemic disease, follicular senescence is the most
Localised scleroderma (morphea) is a rare disease and
the cause and pathogenesis are unknown. Proposed
pathomechanisms include vascular injury or
malfunction, abnormal collagen metabolism and an
immunological mechanism mediated through
humoral and cell-mediated autoimmunity. Lesions
are typically well demarcated, asymptomatic, smooth,
shiny and alopecic. Hypopigmentation may be seen.
The trunk and limbs are most commonly affected
and diagnosis is confirmed by biopsy. Some lesions
recover spontaneously and in others, permanent
scarring results. Changes in hair colour, size and
texture may be seen on regrowth.
Feline acquired symmetrical alopecia
This is a rare condition seen principally in neutered
animals. No breed predilection is reported but
purebred cats are rarely affected. The mean age of
onset is six years but there is a wide (2-12 years)
range. Diffuse thinning of the hair coat, principally
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These multiple choice questions are based on the above
text. Answers appear on page 99.
1. Which of the following statements are INCORRECT:
a. Demodicosis caused by D. gatoi is usually pruritic
and may be contagious.
b. Feline dermatophytosis may cause widespread
c. Dermatophytic pseudomycetomas have been
reported only in the Persian.
d. Skin changes are present in 90% of feline
e. Pili torti is an inherited hair shaft defect seen in
2. Which of the following statements are CORRECT:
a. Alopecia areata is a self-limiting disease caused by a
b. Arthropod bites are the most common cause of
necrotising mural folliculitis.
c. Sebaceous adenitis typically causes a luminal
d. Vellous transformation is seen in pattern alopecia.
e. Cutaneous changes occur in approximately 30% of
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