Case 1

A 9 yr old, 12.6 kg castrated male Cavalier King Charles spaniel was presented with a 6 mo history of pruritus and crusting. Multifocal crusts and moderate hyperkeratosis affected the paw pad margins. There was severe crusting on all claw folds. A well-demarcated erythematous plaque with mild peripheral crusting involved the prepuce and skin within a 2 cm radius around the prepuce. There was moderate crusting of the scrotum. Severe symmetric crusting and erythema affected the perianal region, periocular region, medial aspects of both pinnae, and the lateral muzzle. Histopathology of the skin obtained via punch biopsies confirmed a diagnosis of PF.

Treatment was initiated with prednisolone^b (1 mg/kg per os [PO] q 12 hr) and mycophenolate^c (11.9 mg/kg PO q 8 hr). Six weeks later, adverse side effects from glucocorticoids including muscle wasting, polyuria, and polydipsia were reported by the owner. Upon examination, there was no appreciable response to therapy and crusting of the scrotum had worsened. Cytology from exudative areas revealed large numbers of acantholytic keratinocytes but no bacteria or yeast. Cyclosporine^d (4.7 mg/kg PO q 12 hr) was added as an immunosuppressant. Mycophenolate was continued, and the prednisolone dose was decreased (0.75 mg/kg PO q 12 hr). After 2 mo of prednisolone and mycophenolate therapy, followed by 4 mo of prednisolone, mycophenolate, and cyclosporine therapy, only partial improvement in clinical signs affecting the muzzle and paws was achieved. Mycophenolate was discontinued, and PSGAG injections (4.4 mg/kg subcutaneously [SC] q 4 days) were administered by the owner. Prednisolone (0.43 mg/kg PO q 48 hr) and cyclosporine (4.7 mg/kg PO q 12 hr) therapies were continued. The owner noted a reduction in lesion size at the time of the second injection. A marked reduction in clinical signs was observed at the recheck examination performed after five PSGAG injections (20 days). Crusts on the muzzle had resolved. A mild dermatitis with crusting was present on the interdigital regions, scrotum, and prepuce. Avulsion of crusts revealed minimal erythema. Treatment was unchanged. All clinical lesions were completely resolved upon re-examination 40 days later (Figure 1). A complete blood count (CBC) done at that time was normal. A serum biochemistry panel demonstrated an elevated alkaline phosphatase (623 IU/L; reference range, 15–140 IU/L). This was attributed to glucocorticoid administration. Pre- and postbile acids were shown to be within the reference interval.

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PSGAG injection frequency was reduced to once weekly. After 4 mo of clinical remission, cyclosporine frequency was reduced to every 24 hr. The prednisolone dose was not changed. Within 2 wk, the pemphigus relapsed. Twice-daily cyclosporine dosing was resumed with partial improvement after 30 days. PSGAG injections were subsequently resumed at intervals of 4 days. Again, after only two injections administered 4 days apart, the lesions completely resolved.

The aforementioned treatment plan was continued. Six months later, crusting recurred on the muzzle, scrotum, and paws. The frequency of administration of this dose of PSGAG (4.4 mg/kg) was increased to once every 48 hr and continued indefinitely. Complete remission was achieved again after 2 mo. The prednisolone frequency was decreased 6 mo later to every third day, and the cyclosporine dose remained unchanged. No clinical signs of PF were present after 21 mo total.

Case 2

A 7 yr old, 5.2 kg spayed female Chihuahua mix was referred to the Colorado State University Veterinary Teaching Hospital with a history of histologically confirmed PF that was poorly controlled. Despite 3 mo of treatment with prednisolone (doses ranging from 0.5 to 1.4 mg/kg PO q 12 hr) and cyclosporine (6.73 mg/kg PO q 12 hr), remission was not achieved. On examination, lesions included multifocal crusts, erythema, and purulent exudate involving the medial pinnae, dorsal trunk, and inguinal regions; diffuse truncal and cervical alopecia; and moderate vulvar edema and erythema. Given the lack of response to the current regimen, prednisolone was discontinued. Dexamethasone was prescribed (0.38 mg/kg q 24 hr for 7 days and then decreased to 0.19 mg/kg q 24 hr) along with mycophenolate (9.6 mg/kg PO q 12 hr). Cyclosporine was continued at the previous dose and frequency. Upon examination 14 days later, there was a marked reduction in crusting and erythema. However, the patient had signs consistent with iatrogenic hyperadrenocorticism including cutaneous atrophy, poor hair regrowth, and a pot-bellied appearance. Subsequent attempts over the following 3 mo did not allow for complete discontinuation of dexamethasone without recurrence of the clinical signs of PF. PSGAG (4.6 mg/kg IM every 4 days for 4 wk followed by once-weekly injections) was started in addition to dexamethasone (0.38 mg/kg q 24 hr for 3 days, decreased to 0.19 mg/kg q 24 hr for 5 days, and then to 0.19 mg/kg q 48 hr). Cyclosporine was continued at the same dose and frequency. No lesions were present at the follow-up examination 26 days later. Despite repeated attempts over the following 2 mo to discontinue the dexamethasone, the patient’s PF lesions continued to return with steroid reduction. Mycophenolate was discontinued and replaced with azathioprine (1.9 mg/kg PO q 24 hr)^e while continuing weekly PSGAG, every-other-day dexamethasone (0.19 mg/kg), and twice-daily cyclosporine. Remission was ultimately achieved after 3 wk, and dexamethasone could be reduced to q 72 hr. A CBC showed no significant findings, whereas a serum biochemistry revealed elevated alkaline phosphatase (753 IU/L; reference range, 15–140 IU/L). This was attributed to glucocorticoid administration. Upon recheck, dexamethasone was then reduced (0.19 mg/kg PO q 3 days), and cyclosporine, azathioprine, and PSGAG dosing was unchanged. This regimen maintained 4 mo of remission.

The owner was subsequently unable to present the dog to a veterinarian as directed for PSGAG injections. The dog was presented again to the Colorado State University Veterinary Teaching Hospital as a result of recurring pemphigus lesions after a total of 21 days without a PSGAG injection while maintaining the same dosing regimen of dexamethasone, cyclosporine, and azathioprine. Physical examination findings consisted of mild-to-moderate truncal alopecia, erythema, and adherent scale with a few crusts along the dorsal thorax. PSGAG therapy (4.6 mg/kg IM administered twice weekly) was resumed. The dosing regimen of dexamethasone, cyclosporine, and azathioprine was continued. Four weeks later, physical examination revealed complete hair regrowth, resolution of erythema and crusting, and mild accumulations of adherent scale on the dorsal thorax. Twice-weekly PSGAG injections were continued with cyclosporine and azathioprine. The dexamethasone (0.19 mg/kg) frequency was gradually tapered from every 3 days to every 7 days over an additional 8 wk period. At the time of this writing, 13 mo after starting PSGAG therapy, there was no recurrence of lesions despite reduced frequency of dexamethasone.

Case 3

A 3 yr old, 20 kg spayed female mixed-breed dog was presented with a 2 mo history of crusting dermatitis. On physical examination, the lesions consisted of moderate erythema and hypotrichosis of the muzzle, multiple crusts on the medial aspect of the right pinna and dorsal aspects of the front paws, and crusting of the left flank and perineum. Skin biopsies obtained for histopathology confirmed a diagnosis of PF. Therapy was initiated with prednisolone (1 mg/kg PO q 12 hr), and remission was noted at the 4 wk re-evaluation. Mycophenolate (9.25 mg/kg PO q 12 hr) was started as a steroid-sparing drug at that time while the prednisolone was tapered and discontinued over a period of 6 wk. After an additional 6 wk of mycophenolate monotherapy, crusts returned. There was no cytologic evidence of infectious organisms. Prednisolone (1.1 mg/kg PO q 24 hr) was reinitiated, and mycophenolate was maintained. Upon follow-up examination 6 wk later, the crusts were noted to be resolved. A reduction of the prednisolone dose (0.52 mg/kg q 48 hr) was associated with the development of erythema of the muzzle and exudative crusts affecting the carpal regions. These lesions were seen at the next follow-up examination done 11 wk following the prednisone reduction.

PSGAG injections (4.4 mg/kg SC q 4 days) were administered. Mycophenolate (9.25 mg/kg PO q 12 hr) was continued. Prednisolone was tapered to 0.37 mg/kg q 48 hr over a period of 21 days. There were no lesions at the re-evaluation after six injections were administered. A CBC and serum biochemistry panel revealed no significant findings. Remission was maintained with prednisolone (0.37 mg/kg q 48 hr) along with twice-weekly PSGAG injections and mycophenolate (9.25 mg/kg q 12 hr) for 3 mo. Mycophenolate was subsequently discontinued. Remission was maintained for an additional 2 mo as of the time of this writing.