Lupus erythematosus in 2010 (Proceedings)

Systemic Lupus Erythematosus

This was a commonly diagnosed disease in the late 70s and early 80s. It is rarely diagnosed today. With current day tests for infectious diseases like leishmaniasis and our understanding of the complexities of cutaneous drug reactions, most cases of "lupus" are actually not "lupus" and might be a curable disease.

In this disorder, the animal spontaneously develops autoantibodies to nuclear proteins resulting in a Type III (immune complex) hypersensitivity reaction. The immune complexes that form lodge in small vessels and cause small vessel vasculitis with anoxia of the tissues beyond the vascular damage. The vessels typically affected include those of the kidneys, joint capsules, and skin resulting in a protein-losing nephropathy, shifting-leg polyarthropathy, and pressure point skin lesions, respectively. With the large amount of pyrogens released, fevers are common and can be undulating. Since the cells of the bone marrow contain large amounts of easily accessible DNA, affected animals usually had an anemia, hemolytic or, less commonly, nonregenerative, and/or a thrombocytopenia.

All disorders that produce small immune complexes can cause skin lesions. Pre-existing vessel narrowing is necessary for the immune complexes to lodge in that site. This narrowing is found in the skin at the digits, ear tips, tip of the tail, and over bony prominences. Dogs with pinnae that have bent tips or flop ears can have immune complexes load at the point of folding. The initial lesions are small, hairless, erythematous, and scaly. With time, the lesions enlarge in size and depth and become crusted and ulcerated. These lesions always heal with scarring. The active and scarred lesions are temperature- and photo- aggravated.

The diagnosis of systemic lupus erythematosus is made by skin biopsy, standard hematologic and biochemical tests, serology (ANA titer), and the exclusion of all other possibilities. Serology for all of the infectious disorders present in the region is mandatory as is a complete drug history with withdrawal of suspect agents, especially potentiated sulfa antibiotics.

Treatment is lifelong. Photoprotection is mandatory. Treatment with steroids (prednisolone: 2.2-4.4 mg/kg daily) can be effective but the side effects usually are unsatisfactory. The administration of tetracycyline (250 or 500 mg q8hours) or doxycycline (5 mg/kg q12hours) & niacinamide (250 or 500 mg q8hours) will help improve the skin lesions but will have no effect on the kidney, joint, or other systemic problems. Pentoxifylline (25 mg/kg q12hours) will help the lesions everywhere but probably won't entirely resolve the visceral lesion. Typically azathioprine (2.2mg/kg q24hours) or cyclosporine (5-10 mg/kg q24hours) is added to maintain maximum control of the disease.

Discoid Lupus Erythematosus

The most common "autoimmune" disease of dogs seen in the United States. A rare condition in cats. Always(?) starts in the hairless area at the junction of the nose and bridge of the nose. Historically, many of these dogs have a history which suggests an initial photodermatitis. The photo damage can trigger a permanent epidermal dysplasia with altered cell surface antigens and subsequent rejection type of reaction. The condition is photoaggravated and unprotected exposure to sun light will accelerate the progression of the condition and decrease the response to therapy.

In the typical case, progression up the bridge of the nose or down nose itself is slow. Typically the lesions are superficial but will become deep if traumatized or exposed to intense sunlight or irritant chemicals. Rapid expansion of the lesion; the appearance of similar lesions at distant sites; or a sudden deepening of the lesions suggests that the condition is not discoid lupus.

Beyond the skin lesions these animals are normal as is their routine bloodwork, infectious disease serolology, and ANA titer. Many of the differential diagnoses can be fairly easily dismissed except for mucocutaneous pyoderma. Before skin biopsies are undertaken, the animal should be treated with a minimum 21 day course of an appropriate antibiotic. If no, or minimal improvement is seen, a biopsy to confirm the tentative diagnosis is indicated.

Because the area of involvement is so small, topical treatments can be effective. Potent topical steroids will resolve the inflammation but will cause cutaneous atrophy which predisposes to traumatic scarring. Topical tacrolimus (0.03 to 0.1%) is the preferred topical agent. The systemic agents of choice are tetracycline/niacinamide or pentoxiylline. Photoprotection is absolutely necessary to prevent a photo-induced dysplasia.

Symmetrical Lupoid Onychodystrophy

This is the most common condition where the dog has dry brittle claws on multiple digits of most claws on all 4 feet. The onychodystropy is painful and will induce a bacterial paronychia. The onychodystropy will persist after the infection is resolved and will be recognized on other digits. Treatment is lifelong and a relapse can be expected if drugs are withdrawn. Initial or coincidental treatment with omega-6/omega-3 fatty acid supplements is beneficial in all cases. Other treatments discussed above are applicable here.

Cutaneous Lupus Erthematosus

These are idiopathic cases where the skin biopsies show the histological changes of lupus but the animals are clinically normal and have not laboratory evidence of systemic disease. An occasional animal will have a positive, but low titer, ANA.

Vesicular Cutaneous Lupus

A disorder most commonly seen in Shetland Sheepdogs and Collies. The lesions seen here are ulcerative rather the exfoliative. With the ulceration, initial treatments need to be more aggressive to prevent secondary skin infections.

Exfoliative Lupus Erythematosus

A genetically triggered disease of the German Shorthaired Pointer. Clinical signs recognized early in life, typically by 6 months of age. Dogs with mild skin lesions can act normally but severely affected dogs are depressed, act ill, and can be lame. Skin lesions are very exfoliative and mimic those seen in sebaceous adenitis or leishmaniasis. No uniformly effective treatment reported.