Steven R. Brown1, DVM; Jerry R. Heide2, DVM, PhD; Mike
Glenn3, Curator of Mammals
Hyperkeratosis is described as an increased thickness of the stratum corneum of the epidermis. More specific definitions may be orthokeratotic hyperkeratosis (anuclear) or parakeratotic hyperkeratosis (nucleated cells in the horny layer). Rarely do hyperkeratotic changes suggest an etiologic diagnosis but simply imply altered epidermopoiesis, whether inflammatory, hormonal, neoplastic, or developmental in nature. Diffuse parakeratotic hyperkeratosis has been associated with zinc-responsive dermatosis and vitamin A-responsive dermatoses in dogs.
In the fall of 1991 the Howl Wildlife Center, Lynnwood, Washington was presented with a stranded female harbor seal (Phoca vitulina), approximately four months of age with respiratory compromise that had "numerous small puncture wounds over the entire body-some scabby/pustular". Subsequent care was provided at the Marine Animal Resource Center in Seattle, Washington. Radiographic evaluation demonstrated bronchitis and a possible pulmonary abscess. CBC and serum chemistries were characterized by a leukocytosis (WBC 61,700) with a left shift (bands 11,400). (Table 1) The specific course of treatment that was provided is not recorded. Following clinical improvement she was moved to Point Defiance Zoo, Tacoma, Washington in October 1991.
The following spring (April 1992) Swap, as the harbor seal is now called, moved to her permanent home at the Oregon Coast Aquarium, Newport, Oregon. Upon arrival, she exhibited normal behavior and appetite. However, she had multifocal sites of sparse haircoat with scattered papules, predominately over the truncal area. After several weeks, there was no change noted in Swap's skin condition. Skin scraping and fungal culture were negative. Hematology and biochemical evaluation was considered to be normal (Table 1). Since the gross appearance resembled canine folliculitis-furunculosis, trimethoprim-sulfa (8.8mg/Kg po bid) was initiated without any evidence of adverse reaction. After two weeks there was no change noted in the skin condition. L-thyroxine (1mg po qd) was added to the antibiotic regime for a six week trial. No change was noted in appetite, behavior, or the skin condition.
Subsequently, multiple punch skin biopsies were taken, fixed in buffered 10% formalin and submitted to the Veterinary Diagnostic Laboratory, Oregon State University, Corvallis, Oregon. The pathologist (J.R. Heidel, DVM, PhD) rendered a histologic diagnosis of hyperkeratosis without etiologic indications. Given our limited harbor seal dermatologic case load, the biopsies were further reviewed at the Armed Forces Institute of Pathology, Washington, D.C. (Thomas P. Lipscomb, DVM). Orthokeratotic hyperkeratosis was reconfirmed with speculation as to the significance of gram-negative bacteria noted in the hyperkeratotic crust.
Since Sawp co-habitat's with four harbor seals and six sea lions (Zalophus californianus) without any signs of skin lesions, a transmissible etiologic agent seemed unlikely. In further attempting to determine a cause for the skin condition, blood samples were drawn from Swap and a clinically normal co-habitant harbor seal ("Boots") for mineral and Vitamin A evaluation (Animal Health Diagnostic Laboratory, Lansing, Michigan. (Table 2) There was no conclusive difference between the two seals, serum levels of retinyl palmitate, retinal or the mineral analysis. These results do not support a Zinc or Vitamin A deficiency.
A few weeks after the laboratory evaluations were completed and with no current treatment. Swap's skin lesions started to regress. Sixteen months after her arrival at Oregon Coast Aquarium Swap was clinically normal as compared to her co-habitants. Repeat of the skin biopsy demonstrated an absence of hyperkeratosis. Gram negative bacteria were present on the epidermal surface, and were likely normal skin flora. To date, Swap's skin is clinically normal. Even though, her clinical evaluation was rather extensive her dermatitis remains idiopathic.
The Marine Mammal Dept, Oregon Coast Aquarium, Newport, OR.
1. Small Animal Dermatology Pg. 50-21, Muller Kirk, Scott 4 Edition 1989, Saunders Pub.
2. Tribressen, Coopers Animal Health, Kansas City, KS
3. Soloxine, Daniels Pharmaceuticals, Inc., St. Petersburg, FL
4. Baker Biopsy Punch, Baker Cunnis Pharmaceuticals, Inc., Miami, FL 23178