Moderate to severe, regular to irregular acanthosis of infundibular follicular epithelium with prominent parakeratotic hyperkeratosis that distends/surrounds hair follicles and hair shafts to form follicular casts/comedones

This is a transpeidermal cytotoxic dermatitis with similarity to the hyperkeratotic varient of EM and PNOE

Single cell keratinocyte necrosis, parakeratotic hyperkeratosis, epidermal and follicular (especially the ORS) hyperplasia

May be similar to PLIMFD and hyperkeratotic EM

• Adult-onset
• Collies, Shetland sheepdogs, Border collies
• Transient vesicles--> large ulcers of abdomen/inguinal area/axilla, mucous membranes/pinna (less common)
• Biopsy and clinical features diagnostic
• Previously called "idiopathic ulcerative dermatosis
• Treat with Pentoxyfylline (methylxanthine derivative) used for vasculopathic disorders to increase microvascular blood flow and increase deformability of RBCs; decrease platelet adhesion, also anti-inflammatory properties
• Vitamin E, avoid sunlight and possibly glucocorticoids (careful on muscle wasting)

• Pathogenesis: immune-mediated
• Humans: microangiopathy from aberrant host response to drugs, neoplasia, microbes
• Microvascular injury---> ischemia (skin, muscle, nerve)
• Vasculitis rarely reported in dogs
• Ischemic dermatopathy following rabies vaccine injection- identical lesions

• Hereditary: 
  • exfoliative cutaneous lupus erythematosus of German short-haired pointer, Magyar viszlas
  • Vesicular lupus erythematosus of Shetlands sheepdog, Collie and Border collie

• Acquired: 
  • Localized and generalized discoid lupus
  • Mucocutaneous lupus
  • Systemic lupus erythematosus

• Epidermis (ichthyosis)
• Basement membrane zone (lupus)
• Dermis (Ehlers Danlos, mucinosis)
• Hair follicle (congenital alopecia)

• Form of generalized "ischemic dermatopathy"
• Juvenile collies and Shelties
• Other causes of ischemic dermatopathy- idiopathic vaccine-associated

• Plectin
• Linker protein 500 kd (skin, bone, nervous system); isoforms
• Connects of the cytoskeleton to the cell membrane
• Plectin 1a binds keratin tonofilaments to the hemidesmosomes
• Encoded by PLEC1

• Ischemic dermatopathy is a histologic diagnosis for a group of skin diseases that are characterized by inadequate blood and nutrient supply to the skin
• Types: 
  • Familial dermatomyositis
  • Dermatomyositis-like
  • Rabies-vaccine induced vasculitis with alopecia
  • Vaccine-associated ischemic dermatopathy
  • Idiopathic ischemic dermatopathy

• Clinical features include hyperextensible skin +/- joints and young animal
• Histology can be diagnostic but very subtle
• EM helpful but generally not needed for diagnosis

• A normal feature for the breed
• Excess mucin--> vesicles--> rupture
• Secondary pyoderma
• Increased hyaluronan production

• Suprabasilar acantholysis leads to suprabasilar cleft formation. Clefts can extend to involve hair follicles and sometimes extend deep along the follicle
• Tombstoning- a row of plump basal cells at the base of the cleft, left attached to the basement membrane. When the roof of the bulla becomes detached, this row of tombstone basal cells can be mistaken on low power for an area of ulceration. Close exam of these regions will identify a single row of plump basal cells
• Active acantholysis can be seen above the cleft and free acantholytic cells may be seen within the cleft
• Suprabasilar clefts can transition to form vesicles and bulla. Inflammation is often absent from vesicles and bullae
• Secondary ulceration is common