Skin: congenital and hereditary defect - overview

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Introduction

  • The scientific literature consists of small numbers of reported cases for most conditions.
  • In most conditions the animals should not be used for breeding.
  • Disorders of the surface and follicular epithelium:
  • Disorders of hairs and hair growth:
  • Disorders of pigmentation - hyperpigmentary disorders:
    • Lentigo simplex in orange cats.
    • Tricoloration can be considered a congenital defect.
    • Nevi.
  • Disorders of pigmentation - hypopigmentary disorders    :
  • Disorders of collagen:
  • Behavioral disorders:
  • Atopy    :
    • A criteria for the diagnosis of atopy in other species is that it has a hereditary component. Although atopy is thought to occur in cats currently little evidence of heredity has been published.   
  • Dermatophytosis    :
    • Persians and Himalayans are predisposed to dermatophytosis and to granuloma dermatophytosis.   
  • Idiopathic facial dermatitis:
    • Persians and Himalayans, dirty face syndrome.     
  • Urticaria pigmentosa:
    • Himalayans and Sphinx.
  • Histiocytic mast cell tumours  [Mastocytoma]  :
    • Siamese.

Diagnosis

Clinical signs

Primary seborrhea    

  • Persians. 
  • SeborrheaFig.1 Seborrhea
    An autosomal recessive condition. Either sex and any coat color may be affected. The age of onset is from a few days to a few weeks of age. The coat looks dirty, hairs stick together and there is scale, grease and then alopecia. The cats smell. Waxy debris accumulates in skin folds   (Fig. 1)  .    
  • Biopsy    shows orthokeratotic hyperkeratosis and papillomatosis with a perivascular lymphocytic cellular infiltrate.    
  • Treatment is symptomatic: good grooming, clipping and antiseborrheic shampoo (Paradis & Scott, 1990).     

Ichthyosis

  • Mentioned as having been seen in a litter of cats but the breed was not specified. Cases would be expected to be abnormal at birth and for there to be generalized scale and keratinous projections from the skin surface. Presentation and biopsy for dermatohistopathology should be diagnostic.   
  • If a case is diagnosed in a cat then specialist help should be sought for current treatment options (Scott, Miller & Griffin, 1995).

Aplasia cutis (epitheliogenesis imperfecta)

  • Characterized by areas with an absence of squamous epithelium at birth.
  • Biopsy shows ulceration with absence of epithelium, hair follicles and glands. Infection and death from septicemia are expected depending on the extent of the lesion; small lesions may scar over or be treated using primary closure or skin grafting (Munday, 1970).

Epidermolysis bullosa

  • Siamese and DSH.     
  • A hereditary disease in which trauma induces cutaneous blistering.
  • It has been described in Siamese cats that shed their claws at about 5 weeks of age and an autosomal recessive mode of inheritance was suggested.   
  • A single case reported in a DSH developed at 3 months old and showing paronychia and loss of all claws, ulceration of gums, tongue, palate and oropharynx.   
  • Treatment consists only of reducing the possibility of trauma and preventing/treating any secondary infections. The prognosis depends on the degree of severity (Johstone, 1992; White, 1993; Alhaidari et al , 2005).  

Pili torti

  • Case report of a litter of kittens with all secondary hairs but no primary hairs being affected by the time they were 10 days old. The hairs are abnormal because the hair follicle is distorted leading the hairs to appear flat and rotated.
  • The kittens also had periocular and pedal dermatitis and paronychia.
  • Biopsy showed only follicular hyperkeratosis with occasional cystic dilatation. No treatment is described (Geary & Baker, 1986).   

Shaft disorder of Abyssinian cats

  • Rarely Abyssinian cats have whiskers and primary hairs with a bulbous swelling visible to the naked eye. This is usually at the tip or, if not, the hair often fractures at this site. No treatment is described (Wilkinson & Kistensen, 1989).   

Alopecic breeds ( feline alopecia universalis    )

  • Sphinx.      
  • These cats have been intentionally bred to preserve a characteristic where there are either no hair follicles or the follicles are stunted and reduced in number. Sebaceous and sweat glands and erector pili muscle are similarly affected (Robinson, 1973).    

Congenital hypotrichosis      [Congenital hypotrichosis and alopecia] 

  • Birman     , Burmese     , Devon     and Cornish Rex      and Siamese    .     
  • In Birmans and Siamese the condition has been shown to be autosomal recessive. The histopathology is as in the Sphinx (see above).
  • Affected Burmese kittens had no whiskers, claws, papillae on the tongue or thymus.    
  • Cats are either born hairless or have a poor coat that further deteriorates in the first few weeks of life (Bourdeau, 1988; Casal, 1993; Scott, 1980, Thoday, 1981).  

Feline pinnal alopecia

  • Siamese.
  • Some Siamese cats develop a spontaneous periodic alopecia of the ears, typically bilateral. The alopecia may be patchy or involve most of the surface and usually regrows after a few months.

The Rex mutation

  • Seen in the Devon and Cornish Rex breed.   
  • Kittens have a wavy, woolly hair; adults develop short, curly plush hair. Guard hairs and whiskers are either absent or normal.

Psychogenic alopecia   

  • Siamese and Abyssinian.
  • A predisposition is noted for these breeds to overgrooming as a response to anxiety.    
  • Focal alopecia and sometimes skin ulceration is seen. There may be an obvious environmental factor - new pet or baby, moving house, boarding, loss of companion or threat to territory). The inside of the thighs, the medial forelegs, the caudal abdomen, the dorsal lumbar area and the inguinal region are most commonly affected.    
  • Primary dermatoses are the major differentials especially flea bite hypersensitivity    , atopy    , food hypersensitivity    , and dermatophytosis    , although there are many other conditions in a full differential list.
  • The diagnosis is suspected in a cat of the appropriate breed with a known initiating factor and with ruling out the differentials.   
  • Treatment options include behavioral modification and drug treatments: phenobarbitone  [Phenobarbital]  , diazepam    , fluoxetine    , doxepin, clomipramine    , buspirone, amitriptyline  [Amitryptiline]  , alprazolan.

Tail sucking

  • Siamese cats are prone to lick the distal 2-3 cm of the tail, especially when bored.

Lentigo simplex in orange cats

  • Lentigo simplex of the orange (ginger) catFig.2 Lentigo simplex of the orange (ginger) cat
    This condition consists of scattered macular melanosis appearing on the lips, nose, gingiva, anus and vulva from about 1 year of age in orange cats   (Fig. 2)  .
  • The lesions are thought to be completely benign and should not be treated (Scott, 1987).    

Tricoloration

  • Tricoloration can be considered a congenital defect.     
  • Individuals have either white, black and orange hairs blended together (tortoiseshell) or in patches (calico).

Feline acromelanism  [Hair color changes: temperature induced] 

  • Siamese, Himalayan, Balinese    , and Burmese.
  • These breeds exhibit the effects of a temperature dependant enzyme involved with melanin synthesis so that higher temperatures produce light hairs and lower temperatures produce dark hairs. The points thus display the genetically-programed pigmented skin and hair. This is of no clinical significance other than that any chronic disease that causes locally higher body temperature will cause loss of pigmentation in the area.

Nevi 

  • They are a localized developmental defect that may or may not be congenital.
  • Examples reported in cats include organoid nevi, apocrine sweat gland nevi and pacinian corpuscle nevi. 

- Chediak Higashi syndrome   

  • Persians.  
  • An autosomal recessive disease seen in Persian cats with yellow eyes and blue smoke hair coat color.
  • There is a partial oculocutaneous albinism. There is no clinically significant skin disease, rather the skin/hair coloration it is a marker for concurrent changes to leucocyte morphology, potential immunodeficiency, a bleeding tendency and cataract (Kramer et al , 1977; Prieur, 1987; Kociba, 2000; Cowles, 1992). 

Vitiligo

  • Siamese.  
  • Vitiligo is known to be hereditary in humans although there are autoimmune or neurogenic pathogeneses involved. A hereditary component has not been shown in cats other than that only Siamese have been diagnosed.
  • VitiligoFig.3 Vitiligo
    It shows as macular depigmentation, somewhat symmetrical, on the nose, lips, buccal mucosa and face; starting in young adulthood   (Fig. 3)  .   
  • Histopathology shows only a mild lymphocytic interface dermatitis with an absence of melanocytes (Gross et al , 1992).

Waardenburg-Klein syndrome     

  • An autosomal dominant trait with incomplete penetration it is a defect of migration and differentiation of melanocytes and affected animals show blue eyes, amelanotic skin and hair and deafness. There is no treatment (Guaguere, 1990).    

Cutaneous asthenia   

  • Also known as Ehlers-Danlos syndrome, dermatosparaxis.
  • DSH, DLH, and Himalayan.
  • A group of inherited congenital connective tissue diseases characterized by loose, hyperextensible and abnormally fragile skin that tears easily.
  • Both autosomal dominant and recessive forms have been documented in cats.
  • All forms result in structurally abnormal collagen with reduced tensile strength. Dermal thickness is often markedly reduced.    
  • The clinical signs are present from a young age and show excessively folded hyperextensible skin that is easily torn. Scars may be apparent.
  • A formula for documenting the degree of extensibility have been used. A normal cat has an extensibility index of less than 20.

    Extensibility index  =   (Vertical height of skin fold (dorsolumbar skin)   /    Distance between occipital crest and tail base )  x 100 
        
  • Some individuals have concurrent joint laxity and ocular changes (microcornea, sclerocornea, lens luxation and cataract).    
  • Differential diagnoses might include fragile skin due to exogenous steroid administration or hyperadrenocorticism    although the age of onset and history are expected to be different.
  • Epidermolysis bullosa may also present as a young cat with wounds.    
  • Routine dermatohistopathology may show normal or abnormal collagen fibers, staining with Masson trichrome stain may be useful to demonstrate abnormality.    
  • Affected animal are often euthanazed; otherwise cats should be kept in a secure, atraumatic environment and precautions should be taken to avoid diseases causing pruritus.
  • Wounds should be sutured promptly (Collier, 1980; Counts, 1980; Freeman, 1987; Holbrook, 1980; Patterson & Minor, 1977).   

Atopy       

  • A suggested association with Abyssinian cats has been made (Bettenay V, 1998).

Idiopathic facial dermatitis   

  • Facial dermatitis: Persian catFig.4 Facial dermatitis: Persian cat
    Persians -  dirty face syndrome   (Fig. 4)  .     
  • This condition is seen only in Persian cats but no genetic other links between cases has been shown. There is an accumulation of black, waxy material symmetrically on the face especially in the facial folds.
  • Erythema and excoriation are seen.
  • Ceruminous otitis externa and submandibular lymph node enlargement may be seen (Bond et al , 2000).  

Urticaria pigmentosa

  • Himalayans, Devon Rex and Sphinx.    
  • This proliferative mast cell disorder shows as asymptomatic macular erythema and hyperpigmentation around the mouth,chin, eyes and neck which regresses after a few months (Noli et al , 2004; Tomoko et al , 1999; Vitale et al , 1996).

Histiocytic mast cell tumors  [Mastocytoma] 

  • Siamese.
  • Multiple firm, pinkish plaques occur primarily on the head and pinnae and eventually spontaneously regress (Chastain, 1988; Wilcock, 1986).
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