Pemphigus foliaceus in a juvenile Cashmere goat, and outcome after prednisolone and methylprednisolone therapy

Abstract

A juvenile Cashmere goat was evaluated and treated for generalized pustular and crusting dermatitis. A diagnosis of pemphigus foliaceus was made based on histopathology and immunohistochemistry. Treatment with prednisolone resulted in resolution of the lesions. Despite tapering doses and combination with methylprednisolone for monthly maintenance, the kid was euthanized for poor growth and fiber quality.

A 5-month-old, 20-kg, intact male Spanish Cashmere goat kid was presented to the Western College of Veterinary Medicine (WCVM) Large Animal Clinic, for evaluation of severe pustular and crusting dermatitis of 7 days duration. The kid was part of a small, well-managed herd of 40 goats which received prophylactic hoof care, vaccinations for caseous lymphadenitis, tetanus, blackleg, malignant edema, and pulpy kidney disease (Glanvac 6; Bioniche Animal Health, Belleville, Ontario) and prophylactic treatment for internal and external parasites (Ivomec Injectable; Mérial Canada, Baie d’Urfé, Quebec) 2 wk earlier. The affected kid was behaving normally; eating, drinking, and passing normal feces and no skin lesions were noted by the owners at that time. The diet consisted of free choice alfalfa hay supplemented with mineral and a supplementary pelleted feed. No other animals in the herd were affected. The kid’s sire was euthanized earlier in the year with similar skin lesions which were unresponsive to oral zinc supplementation and repeated antiparasitic treatment.

Case description

Upon presentation to the WCVM (day1), the kid was in good body condition (BCS 3/5) with size and weight assessed as normal for his breed and age. Clinical examination revealed a rectal temperature of 40.0°C [reference interval (RI): 38.5 to 40.0°C (1)], elevated heart rate of 160 beats per min (bpm) [RI: 70 to 120 bpm (1)], and respiratory rate of 40 breaths per min [RI: 20 to 40 breaths/min (1)]. Prescapular lymph nodes were slightly enlarged upon palpation, but all other peripheral lymph nodes were normal in size and consistency. Abnormalities detected on dermatological examination were a generalized non-pruritic exfoliative dermatitis with abundant scale-crust and fewer pustules affecting haired skin with sparing of coronary bands. Pustules were 2 to 5 mm in diameter with irregular margins. Coalescing, circular, alopecic patches (5 to 30 mm) were randomly scattered in a bilaterally symmetrical distribution and reflected sites of non-active lesions. Most severely affected areas were along the dorsum and ventrum of the thorax and abdomen, inguinal and axillary regions, perineal area, neck, and face. Facial lesions involved the lower eyelids, the pinnae and bridge of the nose. The results of the remainder of the physical examination were within normal limits.

Based on the history, physical, and dermatological examination, differential diagnoses for acute onset generalized crusting dermatitis in a young goat included: immune-mediated skin disease like pemphigus, drug eruption, contact irritant (such as chemical burn), infectious disease (bacterial pyoderma, dermatophytosis, dermatophilosis, ectoparasitism), nutritional problem, and neoplasia. Ectoparasitism was considered unlikely given the recent herd treatment, and the acute onset was more typical of autoimmune disease or drug eruption.

Abnormalities on serum biochemistry were limited to a mild hyperglycemia (7.2 mmol/L; RI: 2.3 to 4.7 mmol/L) attributed to stress. Complete blood (cell) count (CBC) was within normal limits. A serum mineral panel screened for magnesium, manganese, iron, cobalt, copper, zinc, selenium, and molybdenum detected marginal manganese level (0.004 ppm; RI: 0.006 to 0.09 ppm); high normal copper (1.36 ppm; RI: 0.8 to 1.2 ppm), and selenium (0.23 ppm; RI: 0.08 to 0.2 ppm) (2). Routine multi-site skin scrapings did not yield evidence of demodex mites, and trichogram analysis did not yield evidence of fungal hyphae, spores, lice, or nits. Aerobic and anaerobic cultures of aseptically collected fluid from pustules were negative. Hair and crust were negative for dermatophyte cultures (a scant growth of Aspergillus fumigatus, a common saprophyte, was deemed irrelevant). Aspirates of pustules consisted of neutrophilic exudates and neutrophils were deemed a mix of healthy and mildly degenerative types. No infectious agents were identified from stained imprints of the undersurface of a freshly removed crust.

Skin biopsies were taken with a 4-mm punch from the thoracic inlet, the right axilla, and the left inguinal regions and submitted with many crusts (peeled off multiple sites from the goat) in formalin for histopathology. Microscopic examination of hematoxylin and eosin stained tissue sections and crust showed a markedly thickened epidermis overlaid by extensive thick layered scale-crust spanning multiple (8 or more) hair follicle openings. Scale-crust was a mixture of fresh and aged, parakeratotic scale alternating with layers of neutrophils, acantholytic keratinocytes, and serum. Acantholytic keratinocytes included rounded and angular types, with the former predominating. Epidermis was moderately acanthotic (regular and irregular types) with extensive subcorneal clefts extending into the spiny layer. Subcorneal clefts and crust were filled with neutrophils in good morphological condition and abundant, rounded-up, nucleated acantholytic keratinocytes which had exfoliated individually and in more extensive sheets. Some of the epidermal clefts were eroded (which may reflect combined effects of fragility of pustules and sampling/processing artefact). Dermal cellularity was increased as a perivascular and neutrophil-rich infiltrate but was milder in comparison to the epidermis and crust. Neutrophilic exocytosis was heaviest in the more superficial keratinocyte layers with neutrophils being closely apposed to and encircling individual keratinocytes (neutrophilic satellitosis, a feature of pemphigus) (Figure 1).

Figure 1.

Base of ruptured pustule from a 5-month-old Spanish Cashmere goat kid highlighting neutrophil traffic in skin (perivascular in dermis and exocytosis in epidermis with satellitiosis in the spiny layer), — *Neutrophils encircle individual keratinocytes. Ultimate exfoliation of acantholytic keratinocytes, individually and in small groups (arrowhead) to the exterior where they are mixed with well-preserved neutrophils. Hematoxylin and eosin stain.

Special stains (Gram’s, Grocott’s, PAS, and Lite Giemsa) were negative for bacteria, dermatophytes, fungi, and Dermatophilus. Immunohistochemistry using direct immunoperoxidase on formalin-fixed tissue sections stained with diamobenzidine-labelled rabbit-anti-goat IgG and counterstained with hematoxylin was limited to a few intercellular clumpy deposits, and was moderately positive for pemphigus foliaceus (PF). Based on clinical signs, and dermatologic, histopathologic, and immunohistochemistry findings, a diagnosis of PF was made. Further classification of the PF as autoimmune (primary PF) versus immune-mediated (secondary PF, whether drug-induced, or associated with other internal disease) could not be determined.

The kid was discharged from the WCVM on day 1 without treatment to be quarantined on the home farm while awaiting the test results; his skin condition worsened during that time. Immunosuppressive treatment was instituted on day 8 with prednisolone acetate (Prednisolone Injection; Vétoquinol, Lavaltrie, Quebec), 1 mg/kg body weight (BW), intramuscularly (IM), q12h. The goal was to slowly taper the dose of prednisolone once remission was achieved, and to eventually discontinue treatment without reoccurrence of clinical signs. Improvement was noted within 3 d of initiating treatment (day 11). Once new lesions were no longer forming (day 15), tapering of the medication was begun, with the dose decreased to 1 mg/kg BW, IM, q24h for 2 wk, then q48h for 3 to 4 more wk. The greatest clinical improvement was seen in the first 2 wk of treatment, after which improvements seemed to slow and plateau. On day 50, while still on prednisolone at 1 mg/kg BW, q48h, the kid began to be lethargic, and have an overall dull and rough hair coat.

Upon re-examination at the WCVM on day 75, it was evident the kid had not continued to grow as well as his herd mates, as he had gained only 3.2 kg in the 10 wk since initial presentation, despite a good appetite. Temperature, pulse, and respiration were within normal limits, and normal feces were passed. Mild exopthalmos was present bilaterally. There was dramatic improvement in the skin over initial presentation; however, the most severely affected areas remained alopecic, fiber had regrown elsewhere but was thin, dull, dry, and lacklustre. Moderate scaling was present over the scrotum, sternum, and around the neck. A blood sample was collected for a repeat CBC and serum biochemistry to check organ function and possible side effects of long-term steroid use. The CBC remained within normal limits, and the only abnormality on serum biochemistry was again mild hyperglycemia. Therapy was changed to maintenance treatment with methylprednisolone acetate (Depo-Medrol; Pfizer Animal Health, Kirkland, Quebec), 0.9 mg/kg BW, IM once monthly for 2 mo, then every 6 to 8 wk. The plan was that if signs reoccurred sooner than 1 mo, alternative therapy or returning to short acting prednisolone would be required.

At 10 mo of age, 166 d after initial presentation, the goat remained pustule and crust free. The tips of the ear pinnae and the bridge of the nose remained hairless, but the rest of his fiber had regrown. His growth was very stunted, and his horns were only half the size of similar aged male goats. The owners were not interested in pursuing alternative therapies (such as gold “salts” or azathioprine) that may have allowed decrease or discontinuation of corticosteroids. Due to his small size and poor fiber quality, the owners decided he had no future as a breeding, meat, or fiber-producing animal, and he was euthanized by a local veterinarian. A necropsy was not performed.

Discussion

On initial presentation, the mildly elevated vital parameters (heart and respiratory rates) were considered to be normal for a stressed goat kid after a 2-hour transport. Mild hyperglycemia on both serum biochemistries was also attributed to stress. The high-normal serum copper and selenium were likely a result of the free choice mineral supplementation the herd was receiving. The scant growth of A. fumigatus from 1 of the swabs was considered not clinically significant.

Pemphigus foliaceus, a rare autoimmune disease of the skin that affects humans, dogs, cats, horses, and goats (3), is one of a group of blistering skin diseases in which intra-epidermal separation results from cell-cell detachment by acantholysis (4). Lack of mucosal involvement separates PF (a superficial pemphigus), from pemphigus vulgaris (PV) (5), which is considered a deep pemphigus. Most of our understanding of PF comes from work in humans, and to a lesser extent dogs. In humans the target of the autoantibodies is desmoglein-1 (dsg1) (5), part of the intercellular adhesion group of proteins. It is uncertain what the autoantigen is in animals with PF, and dsg1 appears to be only a minor autoantigen in dogs (4).

Drug-related PF is important in canine and feline PF (6), and recent vaccination and treatment with injectable ivermectin could have been triggering factors in this case. As both these treatments were repository, they could not be removed or discontinued to see if there would be improvement in the skin condition. There was no evidence on physical examination or CBC and serum biochemistry to support another underlying disease as the trigger for the PF.

To the authors’ knowledge, there are only 5 previous case reports of caprine PF in the English veterinary literature (7–11). The case reported here uses a novel treatment protocol of injectable prednisolone acetate and methylprednisolone acetate. Prednisolone was used to achieve remission of skin lesions, tapered down in dose, and followed by maintenance with monthly methylprednisolone acetate. Oral glucocorticoid treatment was avoided due to the unpredictable absorption in ruminants (12). Injectable prednisolone was chosen over injectable dexamethasone because dexamethasone has 6 times more glucocorticoid potency than prednisolone, and dexamethasone has a long biological half-life compared with prednisolone (36 to 72 h versus 12 to 36 h) (13). Decreasing the frequency of administration of prednisolone to q48h (days 29 to 75) was aimed at reducing side effects of hypothalamic-pituitary-adrenal axis suppression. Both prednisolone and dexamethasone were of comparable cost to the owner.

Table 1 compares the 5 previous and the current case on the basis of gender, age at diagnosis, method of diagnostic confirmation, treatment and outcome. As with other domestic animals (4), there does not appear to be a gender predilection for PF in goats, with 4 females and 2 males represented. There appears to be breed predilection in canine PF (with chows and akitas at highest risk) (4), but the number of diagnosed cases of caprine PF is too small to determine a breed predilection, and 5 breeds are represented in the 6 cases. In all species of animals affected by PF, there is a wide range for age of onset, from juvenile to geriatric (4), and this is no different in goats, with age of onset ranging from 1 mo (11) to 7 y (10). This is in contrast to human PF, where juvenile forms are rare (5). Histopathologic evaluation remains the cornerstone of diagnostics for PF, and all 6 caprine case reports describe lesions typical of PF, with subcorneal or intragranular pustules spanning the length of multiple follicular units, and the pustules containing non-degenerate neutrophils and acantholytic keratinocytes (4). Cytologic evaluation of pustule fluid is often suggestive of a diagnosis of PF, but the pustules are transient and fragile. Suggestive cytologic findings include rafts of free-floating, rounded keratinocytes (acantholytic keratinocytes) and non-degenerate neutrophils with rare eosinophils and without evidence of an infectious agent (bacterial, fungal, or parasitic) (4). Confirmation can be made using immunopathological methods, including direct or indirect immunofluorescence, or immunohistochemistry. Direct immunofluorescence (IF) detects antikeratinocyte autoantibodies (intercellular epidermal IgG autoantibodies) in the epithelium, and is positive in most dogs, horses, and cats with PF. In 3/3 caprine cases where direct IF was used to confirm PF it was positive (7–9). Indirect IF identifies circulating pemphigus autoantibodies in the animal’s serum. This method has been inconsistent in domestic animals (4), and was positive in only 1 of 3 caprine cases where it was used (7–9). Direct immunoperoxidase, the type of immunohistochemistry used in this case, can suffer from lack of sensitivity, as the antigen-antibody complex is not amplified (as in indirect immunoperoxidase), so low concentrations of antigens on the section result in low amounts of staining (14). The exact type of IHC used by Pappalardo et al (10) is not specified, but was positive for intercellular IgG deposits.

Table 1.

Comparison of the 6 reported cases of caprine pemphigus foliaceus by gender, age, breed, method of diagnosis, type of treatment and outcome

Case (reference)	Gender	Age	Breed	Diagnosis	Treatment	Outcome
Scott et al 1984 (7)	F	3 mo	Toggenburg	Histoa, direct IFb	Aurothioglucose	Skin resolved, good growth over 6 mo follow-up while continuing medication
Jackson et al 1984 (8)	M	2 y	Pygmy	Histo, direct IF, indirect IF	Not reported	Not reported
Valdez et al 1995 (9)	F	20 mo	Pygmy	Histo, direct IF	Prednisolone, added aurothioglucose	Skin remission, relapse, discontinuation of medications
Pappalardo et al 2002 (10)	F	7 y	Sardinian	Histo, IHCc	Dexamethasone-21- isonicotinate	Skin resolved, euthanasia for recurrent mastitis while on medication
Cornish and Highland 2010 (11)	F	2 mo	Nigerian dwarf	Histo	Dexamethasone sodium phosphate and gold sodium thiomalate	Skin resolved, productive herd member off medications at 26 mo follow-up
Current report	M	5 mo	Cashmere	Histo, IHC	Prednisolone then methylprednisolone	Skin resolved, euthanized for poor growth/fiber while on medication 5 mo later

^aHistopathology.

^bImmunofluorescence.

^cImmunohistochemistry.

Immune suppression remains the cornerstone of treatment for PF in all species, but with widely varying treatment protocols, durations, combinations, and success rates (6). This is also evidenced by the 5 different treatment protocols in the 5 cases of caprine PF for which treatment was reported (Table 1). Long-term, high doses of corticosteroids are not without risk, and this should always be discussed with clients, and considered when choosing a treatment protocol for PF. This case is the first juvenile case of caprine PF to show complications of treatment; namely signs of iatrogenic hyperadrenocorticism with stunted growth, exophthalmos and poor fiber quality. Side effects were not noted in another kid treated with immunosuppressive doses of dexamethasone (11), or in 1 of the adults treated with the same dose of prednisolone (9). The other adult treated with high dose dexamethasone may have had an adverse effect of becoming more susceptible to infection, as she was euthanized for recurrent bacterial mastitis (10). Considerations for minimizing adverse effects of corticosteroid treatment may include use of cytotoxic drugs (azathioprine, cyclophosphamide, or chorambucil) such as are routinely used in canine PF, alone or in conjunction with lowered dosages of corticosteroids (4). Owners of livestock treated with these drugs would have to make assurances that the animal or its by-products would never enter the human food chain. Alternatively, use of chrysotherapy (gold compounds) for immune modulation proved useful in 1 of the 2 caprine cases where it was used (7,9). Not much is known about the mechanisms of chrysotherapy and how it aids in immune modulation, but often treatment is required for several months before beneficial effects are seen (7).

Skin lesions resolved completely in all 5 cases for which treatment and outcome were reported. Only 1 of the 5 cases was able to remain lesion-free with discontinuation of treatment (11). Discontinuation of medication resulted in relapse in 1 case (9), and discontinuation of medication was not attempted during the follow-up period reported in the other cases (7,10) including the case of this current report. These results are in line with reports of equine PF, where less than 1/3 of patients that achieved remission were maintained in the absence of treatment (15). In contrast, not all equine patients were even able to achieve remission with treatment, and just over 1/3 of patients were euthanized for medical complications, financial constraints, or lack of response to treatment (4,15).

This report suggests a possible inherited genetic component of PF in goats, as the affected kid’s sire had a clinically identical syndrome that was unresponsive to antibiotics, anti-parasitics, and zinc supplementation. That goat was euthanized by the regular herd veterinarian without obtaining and examining skin biopsies to make a definitive diagnosis, but it made the owners very attentive to the first signs of skin disease in this kid. All other reports of caprine PF have had no other goats on farm, or no other affected goats in the herd.

The number of cases of reported caprine PF may be underestimating the true population prevalence of disease, if herd economics limit diagnostic and veterinary treatment costs for a single animal (if empirical treatment with antibiotics and anti-parasitics do not show any improvement, the animal may be culled from the herd without further work-up). Breeds kept as pets (such as dwarf and pygmy breeds), therefore, may be over-represented.

This case report highlights the clinical signs of this rare skin disease in goats, the importance of ancillary diagnostics in addition to a thorough physical examination to diagnose pemphigus foliaceus, and the potential side effects of immunosuppressive therapy in caprine autoimmune skin disease. We suggest that pemphigus foliaceus be considered high on the differential diagnosis list in goats with generalized exfoliative, pustular skin disease with scaling and crusts, particularly in those cases refractory to empirical treatment with anti-parasitics and antibiotics.