Dermatology: AUTOIMMUNE/IMMUNE-MEDIATED

 

  •  Juvenile cellulitis/ puppy strangles supposedly caused by vaccine reaction however has not been proven. However there is a possibility of predisposition due to mother's nutrition or puppy nutrition prior to weening or due to selected formula after weening.  














  • Faces will swell up with cellulitis, crusty and oozing faces
  • Middle dog has been treated with immunosuppressive doses of steroids for 4 weeks. Submandibular lymphodes get extremely large which can eventually cause strangling of puppy "puppy strangles"

Demodicosis (Red Mange)

Cause: Overgrowth of Demodex mites, normally present in small numbers on healthy skin.

Appearance: Redness, hair loss (alopecia), scaling, and sometimes secondary infections.

Forms:

Localized: Small patches, often in young dogs; may resolve spontaneously.

Generalized: Widespread lesions, more severe; may require long-term treatment.

Commonly affected areas: Face, forelegs, around eyes, and paws.

**Note: Often linked to immune dysfunction; not typically contagious to humans

PYODERMA (Bacterial Skin Infection)
Location:  Trunk,  warm spots (armpits and groins), sometimes upper legs never the feet 

Cause: Overgrowth of bacteria, often Staphylococcus species, on the skin.

Appearance: Redness, pustules, crusts, collarettes (ring-shaped lesions), hair loss, and sometimes odor.

Types:

Surface: Affects outer skin layers, often linked to allergies or parasites.

Superficial: Involves hair follicles (One single follicle per pustule), commonly causes pustules. Never see gold crust in Pyoderma

Deep: Extends into deeper skin layers; may cause ulcers or nodules.

Predisposing factors: Allergies, parasites, endocrine disorders (e.g., hypothyroidism, Cushing’s), trauma, or immune suppression.

Treatment: Topical or systemic antibiotics, addressing underlying causes (Diet trial and treat or outer trigger sources elimination).





TRICHOPHYTON MENTAGROPHYTES

Fungus culprit: Ringworm 
  •  Not itchy 
  • However deep ulcers will develop
  • History of dog: All started after a hike in the woods
Abnormal visible symptoms


  • Lost cobble stone appearance, looks like we are crossing nasal planum into regular skin 
  • Immune related problem: Discoid Lupus Erythematosus or Pemphigus Foliaceus 
    • Plasma cells are infiltrating and pushing cells apart stretching the skin causing loss of cobble stone effect 
Discoid Lupus Erythematosus (DLE) in Dogs
  • --Definition: Autoimmune skin disease primarily affecting the face and nose, causing localized depigmentation, scaling, and erosions.
  • Appearance: Redness, crusting, depigmentation, erosions, ulceration, and sometimes scarring; typically affects the nasal planum, lips, and periocular areas.
  • Triggers/Precipitating Factors:
    • Genetic predisposition (certain breeds like Collies, German Shepherds, and Siberian Huskies)
    • Sunlight/UV exposure (can exacerbate lesions)
    • Dietary triggers: Food antigens or sensitivities may worsen immune-mediated reactions in some dogs.
  • Management:
    • Topical or systemic immunosuppressive therapy (corticosteroids, tacrolimus
    • Sun protection (sunscreens or limited sun exposure)
    • Supportive skin care and monitoring for secondary infections
**DLE lesions are often localized to the face and nose, and may flare with sunlight or dietary sensitivities, highlighting the importance of environmental and dietary management alongside medical therapy.



Vasculitis (Nasal arteritis)  
  • . Whatever triggers causes immune complexes. 

  • Appearance: Crusts on the nose, depigmentation, erosions, or ulcerations. Ulcers in the center of the outer nose. Inflamed blood vessels and arteries cause an immune-mediated response which leads to inflammation within the skin and upon the outer skin of the nasal planum.

  • Potential Triggers:

    • Immune-mediated reactions

    • Environmental factors

    • Dietary triggers: Certain food antigens or intolerances may exacerbate immune responses. Common culprits include beef, dairy, wheat, or novel protein sensitivities.

  • Management:

    • Identify and eliminate dietary triggers

    • Supportive care for nasal lesions

    • Anti-inflammatory or immunosuppressive therapy if indicated


Pemphigus (Autoimmune Skin Disease in Dogs)
  • Gold crust over muzzle and nose. Pustules, erosions, hair loss, and redness; commonly affects nose, foot pads, and ears.
  • Losing cobble stone appearance, Top picture early stage. Bottom picture advanced stage
  • Definition: Autoimmune disorder where the body attacks its own skin cells, causing blisters and pustules.
Types:
  • Pemphigus foliaceus – most common; affects superficial skin layers.
  • Pemphigus vulgaris – rare; deeper skin layers involved.
Triggers/Precipitating Factors:
  • Genetic predisposition
  • Immune dysregulation
  • Medications or infections
  • Dietary triggers: Food antigens or sensitivities (e.g., beef, dairy, wheat, or novel proteins) may exacerbate immune responses.
Management:
  • Immunosuppressive therapy (e.g., corticosteroids, cyclosporine)
  • Treat secondary infections if present
  • Supportive skin care
  • Lesions on nasal planum, foot pads, and mucocutaneous junctions may indicate systemic autoimmune involvement, sometimes worsened by dietary triggers.

Hypotrichosis (Reduced Hair Growth in Dogs) and Mucocutaneous Pyoderma no gold crust




  • Definition: Partial or complete loss of hair or failure of hair to grow normally, often congenital or acquired.

  • Appearance: Sparse or absent hair, thinning coat, sometimes patchy alopecia; skin may appear normal or slightly thickened.

  • Causes/Triggers:

    • Genetic/congenital defects (certain breeds predisposed)

    • Endocrine disorders (e.g., hypothyroidism, Cushing’s disease)

    • Nutritional deficiencies (protein, essential fatty acids, zinc)

    • Dietary triggers: Inadequate nutrition or food sensitivities can exacerbate hair loss.

    • Chronic skin disease or inflammation

  • Management:

    • Treat underlying endocrine or nutritional deficiencies

    • Provide balanced diet with essential nutrients

    • Supportive skin and coat care

**Hypotrichosis highlights the importance of evaluating genetics, endocrine health, and diet, as hair growth is closely linked to overall systemic and skin health.

Mucocutaneous Pyoderma (Dogs)

Definition: Bacterial skin infection affecting the mucocutaneous junctions (lips, eyelids, genital areas) without forming the classic “gold crust.”

Appearance: Redness, erosions, pustules, ulceration, and occasional hair loss around mucocutaneous junctions; collarettes may be present.

Causes/Triggers:

  • Bacterial overgrowth (commonly Staphylococcus species)

  • Underlying immune dysfunction or endocrine disorders

  • Dietary triggers: Food antigens or sensitivities can exacerbate immune-mediated responses at mucocutaneous sites.
  • Trauma or irritation at junctions
Management:

  • Systemic or topical antibiotics based on culture/sensitivity

  • Treat underlying predisposing factors

  • Supportive care for erosions and ulcerations

**Lesions often appear at lips, eyelids, and genital junctions, highlighting the role of immune health, underlying disease, and dietary factors in mucocutaneous pyoderma.

Oral/Mucosal Evaluation in Dogs

Always examine the mouth: Many immune-mediated skin diseases and food-related toxicities manifest lesions inside the oral cavity.

Signs to watch for: Redness, erosions, gums (dental disease eliminate and yet erosions, painful, bleeding gums are still present), ulcers, or crusts on gums, palate, and inner lips.

Causes/Triggers:

  • Immune-mediated diseases (e.g., pemphigus, lupus)

  • Food toxicities or sensitivities

  • Viral or bacterial infections

  • Trauma or irritation

Clinical relevance: Oral lesions often appear before or alongside skin manifestations, helping identify systemic or dietary triggers early.

Ontario Association of Veterinary Technicians. (2022). [Dermatology]. Brought to you by OAVT Seminar.

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