Congenital Diseases

CHAPTER | 10 Congenital Diseases




image Epidermolysis Bullosa

image Familial Canine Dermatomyositis

image Ichthyosis

image Ehlers-Danlos Syndrome (cutaneous asthenia, dermatosparaxis)

image Cutaneous Mucinosis

image Dermoid Sinus

image Canine Juvenile Cellulitis (juvenile pyoderma, puppy strangles)


Epidermolysis Bullosa



Features


Epidermolysis bullosa refers to a group of hereditary mechanobullous diseases in which minor trauma results in blister formation. Structural defects in the basement membrane zone are responsible for incomplete cohesion between the epidermis and the dermis. The condition is rare in dogs and cats, with affected animals usually developing lesions shortly after birth.


Vesicles, bullae, erosions, crusts, and ulcers appear at sites of frictional trauma such as on the footpads, lips, gingiva, tongue, and palate, and over bony prominences of the limbs. Lesions may also involve the face, trunk, tail, or ventral abdomen. Claw sloughing and secondary bacterial paronychia may be seen. In some forms of the disease, in addition to oral vesicles and ulcers, other parts of the upper digestive tract (e.g., esophagus) are similarly affected.



Top Differentials


Differentials include dermatomyositis, pemphigus vulgaris, bullous pemphigoid, systemic lupus erythematosus, cutaneous vesicular lupus erythematosus, erythema multiforme/toxic epidermal necrolysis, drug eruption, and vasculitis.



Diagnosis



1 Rule out other differentials.

2 Dermatohistopathology: subepidermal clefting and vesicle formation with minimal inflammation.

3 Electron microscopy (skin biopsy specimens): depending on the subtype of epidermolysis bullosa, clefting may be intraepidermal from cytolysis of basal cells, below the lamina densa, or within the lamina lucida of the basement membrane zone.


Treatment and Prognosis



1 No specific treatment is known.

2 Trauma should be avoided by keeping the affected animal indoors, away from other animals, and handling it carefully.

3 Appropriate systemic antibiotics should be administered as needed for secondary bacterial infection.

4 The prognosis for severely affected animals is poor. With proper environmental management, mildly affected animals may enjoy a reasonable quality of life. Affected animals should not be bred.

image

FIGURE 10-1 Epidermolysis Bullosa.


Ulceration of the ear pinna.


(Courtesy P. Rakich.)


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FIGURE 10-2 Epidermolysis Bullosa.


Sloughing of the footpads. The superficial epidermis is peeling off.


(Courtesy P. Rakich.)


image

FIGURE 10-3 Epidermolysis Bullosa.


Ulcerations on the tongue of the young kitten. The primary lesions are vesicles, which easily rupture, leaving ulcers.


(Courtesy A. Wolf.)



Familial Canine Dermatomyositis



Features


Familial canine dermatomyositis is an inherited inflammatory disorder of the skin and muscles in which a microvascular vasculopathy is thought to play a role. The cause is unclear, but a genetic predisposition followed by a trigger (e.g., infection, other environmental factor) that initiates an immune-mediated process and the clinical signs has been proposed. It is uncommon in dogs, with the highest incidence in collies, Shetland Sheep dogs, and their cross-breeds. Lesions usually first appear in puppies at between 2 and 6 months of age. Several littermates may be affected, but the severity of the disease often varies significantly among puppies.


Skin lesions are nonpruritic, vary in severity, and may wax and wane. They are characterized by variable degrees of erythema, alopecia, scaling, crusting, erosion, ulceration, and scarring and, rarely, by papules and vesicles. Skin lesions occur on the bridge of the nose, around the eyes and lips, in the inner ear pinnae, on the tail tip, and over bony prominences of the distal extremities. Rarely, footpad ulcers are seen. Signs of muscle involvement are variable. Dogs may appear to be unaffected, to have bilaterally symmetrical atrophy of the masseter or temporalis muscle, or to have generalized symmetrical muscle atrophy. Dogs with masseter muscle involvement may have difficulty eating, drinking, and swallowing. Severely affected dogs may be weak, lethargic, stunted, lame, and infertile. If the leg muscles atrophy, affected dogs may exhibit an abnormal “high-stepping” gait. When the esophageal muscles are affected, megaesophagus may develop.



Top Differentials


Differentials include demodicosis, dermatophytosis, superficial pyoderma, autoimmune skin disease, vasculitis, and polymyositis.



Diagnosis



1 Rule out other differentials.

2 Dermatohistopathology (may be nondiagnostic): scattered epidermal basal cell degeneration; perifollicular inflammatory infiltrates of lymphocytes, histiocytes, and variable numbers of mast cells and neutrophils; follicular basal cell degeneration; and follicular atrophy are highly suggestive findings but may not be present, especially in chronic or scarred lesions.

3 Electromyography: fibrillation potentials, bizarre high-frequency discharges, and sharp waves are seen in affected muscles.

4 Histopathology (muscle biopsies): variable multifocal accumulations of inflammatory cells, including lymphocytes, macrophages, plasma cells, neutrophils, and eosinophils; myofibril degeneration; and myofiber atrophy and regeneration.


Treatment and Prognosis



1 Symptomatic shampoo therapy may be helpful for removing crusts.

2 Any secondary superficial pyoderma should be treated with appropriate systemic antibiotics.

3 Activities that may traumatize the skin should be avoided.

4 Intact females should be spayed because estrus, pregnancy, and lactation exacerbate the disease. Affected males should be neutered so they cannot reproduce.

5 Daily supplementation with oral essential fatty acids and treatment with vitamin E 400 to 800 IU PO every 24 hours may be beneficial for the skin lesions. Improvement should be seen after 2 to 3 months of therapy (see Table 8-2).

6 Treatment with pentoxifylline (Trental) 25 mg/kg PO every 12 hours with food may be beneficial in some dogs. Improvement should be seen within 1 to 3 months of therapy.

7 Cyclosporine (Atopica) 5–10 mg/kg PO administered every 24 hours may be beneficial (effects are seen in approximately 4–6 weeks). Then, dosage frequency should be tapered down to every 48 to 72 hours. Glucocorticoids can be used initially to speed response. As of this writing, no statistically significant increase in tumor risk or severe infection is known to result from the immune effects of cyclosporine.

8 Prednisone 1 mg/kg PO every 24 hours until lesions improve (approximately 7–10 days), then tapered off, may be used for acute flare-ups; however, prolonged steroid usage may exacerbate muscle atrophy.

9 The prognosis is variable, depending on the severity of the disease. Skin lesions in minimally affected dogs tend to resolve spontaneously, with no scarring. Skin lesions in mildly to moderately affected dogs usually resolve eventually, but residual scarring is common. Even when lesions resolve, however, relapses may occur later on, when the dog is an adult. In severely affected dogs, dermatitis and myositis do not resolve, and the prognosis for long-term survival is poor. Regardless of disease severity, affected dogs should not be bred.

image

FIGURE 10-4 Familial Canine Dermatomyositis.


Erosive lesions on the periocular skin are characteristic of active lesions. As the dog ages and active lesions resolve, the skin may become scarred and remain alopecic.


(Courtesy M. Mahaffey.)


image

FIGURE 10-5 Familial Canine Dermatomyositis.


The same dog as in Figure 10-4. Active lesions have resolved, leaving alopecic, scarred skin.


(Courtesy M. Mahaffey.)


image

FIGURE 10-6 Familial Canine Dermatomyositis.


Alopecia and scarring on the face of an adult collie. The erythematous macules were active lesions.


image

FIGURE 10-7 Familial Canine Dermatomyositis.


Alopecic, erythematous, crusting dermatitis on the tail of a collie with dermatomyositis.


image

FIGURE 10-8 Familial Canine Dermatomyositis.


Severe muscle atrophy on the lumbar musculature in an infected dog. The lateral processes of the vertebrae can be easily palpated.


(Courtesy D. Angarano.)


image

FIGURE 10-9 Familial Canine Dermatomyositis.


Crusting, erosive lesions on the ear pinna of an adult collie with chronic lesions.


image

FIGURE 10-10 Familial Canine Dermatomyositis.


Crusting lesions on the ear margin waxed and waned for several years. Note the similarity to vasculitis and other autoimmune skin diseases.


image

FIGURE 10-11 Familial Canine Dermatomyositis.


Alopecia and scarring typical of chronic lesions.

Related posts:

  1. Diagnostic Techniques
  2. Viral, Rickettsial, and Protozoal Skin Diseases
  3. Fungal Skin Diseases
  4. Avian and Exotic Animal Dermatology

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Sep 10, 2016 | Posted by in SMALL ANIMAL | Comments Off on Congenital Diseases

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