Page 672 - Cote clinical veterinary advisor dogs and cats 4th

309.e2 Erythema Multiforme and Toxic Epidermal Necrolysis

Erythema Multiforme and Toxic Epidermal Necrolysis
VetBooks.ir

PHYSICAL EXAM FINDINGS
BASIC INFORMATION
clearly distinguish an EM from an SJS/TEN.
• The animal can be debilitated, especially with that histologic criteria by themselves cannot
Definition TEN.
Spectrum of acute, potentially life-threatening, • Fever precedes virtually all cases of TEN in Differential Diagnosis
uncommon to rare mucocutaneous diseases humans. Differentiation can be based on history (in
defined by distinctive clinical and histopathologic • In more severe cases, internal organ function contrast to burns), time course (EM-TEN
findings. These diagnoses are considered if derma- may be affected, including mucosa other than typically worsens rapidly, unlike urticaria, which
tologic findings include annular (target) lesions, oral. tends to improve spontaneously and quickly),
erythematous eruptions, and/or epidermal/ and ultimately histopathologic appearance.
mucosal detachment with secondary ulcerations. Etiology and Pathophysiology • Superficial and deep infection (bacterial,
• Although the spectra encompassing EM and fungal, parasitic)
Synonyms SJS/TEN appear to be immune mediated, • Urticaria
Stevens-Johnson syndrome, overlap syndrome, the pathomechanisms differ. A cell-mediated • Cutaneous adverse drug reaction
Lyell’s syndrome immune response directed toward various • Autoimmune dermatitis (pemphigus complex,
antigens on the surface of the keratinocytes is lupus erythematosus, bullous pemphigoid,
Epidemiology suspected in EM, and a defective epidermal epidermolysis bullosa)
SPECIES, AGE, SEX detoxification of drug byproducts, in addition • Vasculitis
Dogs and cats of any age and both sexes to the cellular immune reaction, is proposed • Burns
to explain TEN. • Ulcerative stomatitis
RISK FACTORS • Both processes lead to keratinocyte apoptosis • Epitheliotropic lymphoma
• In dogs and cats, erythema multiforme secondary to the direct cellular cytotoxicity • Toxic shock syndrome
(EM) has been associated with drug therapy (EM) or by the activation of specific cell • Superficial suppurative necrolytic dermatitis
(19%-59% of cases reported), neutraceutical death mediators (SJS/TEN).
products, beef/soy commercial dog food, infec- • Overproduction of cytokines by cytotoxic Initial Database
tions (herpesvirus [suggested], parvovirus, and T lymphocytes may play a major role • No specific laboratory findings, although the
Pneumocystis pneumonia) or is idiopathic. by upregulating the adhesion molecules, CBC, biochemistry profile, and urinalysis will
• Toxic epidermal necrolysis (TEN) is usually recruiting lymphocytes, and contributing allow assessment of systemic health and aid
associated with drug therapy but can be to keratinocyte apoptosis. treatment planning (e.g., prerenal azotemia
idiopathic. must be addressed)
• The most common drugs reported as trigger- DIAGNOSIS • Routine dermatologic diagnostic tests should
ing EM/TEN are trimethoprim-potentiated be performed as appropriate (skin scrapings,
sulfonamides, penicillins, cephalosporins, Diagnostic Overview skin cytology, skin biopsy, fungal culture)
levamisole, and phenobarbital (TEN). The skin lesions are pleomorphic (varied in based on differential diagnosis.
shape and appearance). Acute-onset skin lesions,
Clinical Presentation particularly with epidermal detachment, signs of Advanced or Confirmatory Testing
DISEASE FORMS/SUBTYPES systemic illness, and a history of ongoing medi- • Skin biopsy is required for diagnosis.
• Based on clinical and histopathologic fea- cation administration (or some combination of Hallmark histopathologic findings include
tures, the EM-TEN spectrum in veterinary these features), should prompt consideration hydropic degeneration, single-cell apoptosis
dermatology was classically divided into five of skin biopsies to confirm the diagnosis. Note to full-thickness necrosis of the epidermis,
different categories: EM minor, EM major,
Stevens-Johnson syndrome (SJS), overlap
syndrome (OS), and TEN.
• In human dermatology, classification of the
EM-TEN spectrum has been revised based
on the Severe Cutaneous Adverse Reaction
(SCAR) study. According to this classifica-
tion there are separate entities rather than a
spectrum. EM is divided into EM minor and
EM major (the latter consisting of a group
of typical/atypical EM major) and the SJS/
TEN consists of a continuum from SJS to
TEN.
• The classification in veterinary dermatology
is still debated, without consensus.
HISTORY, CHIEF COMPLAINT
Severe skin/mucosal lesions are usually the main
complaints, often accompanied by systemic
illness. This dermatosis has an acute onset with
rapid deterioration. Recent (preceding) drug
administration can be an important element
of the history, along with recent infection or ERYTHEMA MULTIFORME Idiopathic erythema multiforme in a Samoyed with lingual mucosa detachment.
diet change. (Courtesy of Dr. Frédéric Sauvé.)

www.ExpertConsult.com