How to manage suspected cases of ProMeris-triggered pemphigus foliaceus

ProMeris-triggered pemphigus foliaceus should be on the differential diagnosis list for any dog that presents with skin lesions between its shoulder blades and has a history of ProMeris application, even if the preventive application began months before the onset of clinical signs. Treatment and prognosis vary depending on the lesion pattern.

Contact ProMeris-triggered pemphigus foliaceus

Dogs with this disease develop skin lesions (e.g. crusting, alopecia, erythema) at the preventive application site but not at areas distant from it. Systemic signs (lethargy, fever, pain, anorexia, lameness) may be present in some dogs.

How to diagnose it

• Perform a cytologic examination of visible purulent exudate, and look for acantholytic epidermal cells typical of pemphigus foliaceus.

• Take several biopsy samples from recent skin lesions, preferably from intact pustules, and submit them for routine histologic examination. If pustules are not available, crusted lesions are adequate. Do not surgically scrub the lesions. If the crusts fall off during biopsy, submit them in the same container as the biopsy sample with a note to the pathologist that crusts are present in the formalin. Microscopic lesions are identical to those of typical autoimmune pemphigus foliaceus.

How to treat it

• Do not reapply ProMeris.

• Wash the area.

• Apply a mid- to high-potency topical glucocorticoid (e.g. triamcinolone acetonide [Genesis Topical Spray—Virbac Animal Health]) at the site of skin lesions once or twice daily as needed.

• If systemic signs are absent, add oral glucocorticoids at anti-inflammatory dosages (e.g. 1 mg/kg/day of prednisone or a similar drug).

• If systemic signs are present, add oral glucocorticoids at immunosuppressive dosages (e.g. 2 to 4 mg/kg/day of prednisone or a similar drug).

• If signs do not undergo clinical remission within one month or if they recur after dose tapering, add another oral immunosuppressant such as azathioprine (2 mg/kg/day) or cyclosporine (7 to 10 mg/kg/day).

• Treat until clinical remission of lesions, and taper drug doses progressively until withdrawal.

Prognosis is normally good with most dogs likely to achieve complete disease remission and complete drug withdrawal. Oral immunosuppressant therapy may be prolonged in some patients.

Generalized ProMeris-triggered pemphigus foliaceus

Dogs with this disease develop skin lesions (e.g. crusting, alopecia, erythema) at the preventive application site and later develop skin lesions at sites distant from the application area. Systemic signs (lethargy, fever, pain, anorexia, lameness) are present in most dogs.

How to diagnose it

• Perform a cytologic examination of visible purulent exudate, and look for acantholytic epidermal cells typical of pemphigus foliaceus.

• Take several biopsy samples from recent skin lesions, preferably from intact pustules, and submit them for routine histologic examination. If pustules are not available, crusted lesions are adequate. Do not surgically scrub the lesions. If the crusts fall off during biopsy, submit them in the same container as the biopsy sample with a note to the pathologist that crusts are present in the formalin. Microscopic lesions are identical to those of typical autoimmune pemphigus foliaceus.

How to treat it

• Do not reapply ProMeris.

• Wash the area.

• Apply a mid- to high-potency topical glucocorticoid (e.g. triamcinolone acetonide [Genesis Topical Spray—Virbac Animal Health]) at the site of skin lesions once or twice daily as needed.

• Administer oral glucocorticoids at immunosuppressive dosages (e.g. 2 to 4 mg/kg/day of prednisone or a similar drug).

• If signs do not undergo clinical remission within one month or if they recur after dose tapering, add another oral immunosuppressant such as azathioprine (2 mg/kg/day) or cyclosporine (7 to 10 mg/kg/day).

• Treat until clinical remission of lesions, and taper drug doses progressively until withdrawal, if at all possible.

The prognosis is generally good, with most dogs likely to achieve complete disease remission and complete drug withdrawal. Oral immunosuppressant therapy may be prolonged in some patients.