Page 1301 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1276 CHAPTER 12

VetBooks.ir 12.76 12.77

Fig. 12.76 Drug eruption in a 5-year-old Fig. 12.77 Equine cutaneous lupus erythematosus.
Thoroughbred mare developing immediately after
intravenous injection of pethidine and acepromazine.

Clinical presentation Aetiology/pathophysiology
A non-specific skin eruption occurs. It may mimic CLE is an autoimmune disease. The pathogenesis is
urticaria, with papules, vesicles and generalised pru- multifactorial and may be localised to the skin only
ritus (Fig. 12.76). or, in more severe cases, may induce multisystemic
signs of autoimmune attack, including polyarthritis,
Diagnosis vasculitis and dermatitis.
Diagnosis is very difficult unless the onset is acute.
Presumptive evidence may be obtained if drugs are Clinical presentation
withdrawn and the signs disappear, then reappear There is a sharp demarcation between pigmented
with reintroduction of the suspect drug. True cau- and depigmented areas. Depigmentation is seen
sality can be proven by reintroducing the drug and around the eyes, lips, nostrils, vulva, anal ring and
having the signs recur, but this is rarely done. prepuce (Figs. 12.78, 12.79). Loss of pigment can
be gradual or rapid. Erythema and scaling with
Management alopecia occur, causing the skin of long-standing
Suspected drugs should be discontinued. If a severe cases to look like wrinkled leather. ANA testing is
reaction occurs, systemic glucocorticoids may be negative in CLE. Horses with systemic lupus ery-
administered, but the response may be poor. thematosus (SLE) may also show organ dysfunction,
weight loss and fever. Horses with SLE often have a
Prognosis positive ANA titre.
The prognosis is good if the offending drug can be
identified and discontinued. Diagnosis
Skin biopsy is used for diagnosis and is character-
EQUINE CUTANEOUS LUPUS ised by a lymphocytic interface dermatitis with
ERYTHEMATOSUS prominent basilar keratinocyte death by apoptosis.
Specimens should be placed in formalin for con-
Definition/overview ventional histopathology and possible immunohis-
Equine cutaneous lupus erythematosus (CLE) is tochemistry evaluation. Additional samples should
a rare, incompletely defined, clinicopathological be acquired and placed in Michel’s medium if being
entity found in the horse and differing in many submitted for immunofluorescence studies. Serum
instances from the classic forms seen in humans for an ANA test and quantification of IgM and/or
and dogs (Fig. 12.77). IgG may also be submitted.