Equine Dermatology

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Equine Dermatology

• Nodular Skin Diseases

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What are the major causes of Nodules?
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What are the major causes of Nodules?

• Inflammatory
• Parasites
• Collagenolytic Granulomas/Eosinophilic Granulomas
• Habronema
• Hypoderma
• Tick bite granulomas
• Infections (Fungal/Fungal-like)
• Sporotrichosis
• Phaeophymycosis
• Eumycotic mycetomas
• Zygomycosis
• Other mycoses (dermatophyte kerion, blasto,
  crypto)
• Pythiosis

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What are the major causes of Nodules?

• Inflammatory
• Infections (Bacterial)
• Furunculosis
• Dermatophilosis
• Ulcerative lymphangitis (Corynebacterium
  pseudotuberculosis)
• Actinomycosis
• Nocardiosis
• Abscesses
• Mycobacterial infections (TB)
• Glanders

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What are the major causes of Nodules?

• Inflammatory
• Viral
• Vaccinia
• Immunologic
• Urticaria
• Erythema multiforme
• Amyloidosis

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What are the major causes of Nodules?

• Inflammatory
• Miscellaneous
• Dermoid/follicular cysts
• Eosinophilic granulomas
• Axillary nodular necrosis
• Unilateral papular dermatosis
• Exuberant granulation tissue
• Panniculitis
• Hematoma
• Foreign body granulomas

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What are the major causes of Nodules?

• Neoplastic
• Papilloma
• Aural plaque
• Squamous cell carcinoma
• Sarcoid
• Melanoma/melanocytoma
• Mast cell tumor
• Basal cell tumor
• Fibroma/fibrosarcoma
• Hemangioma/hemangiosarcoma
• Lipoma
• Lymphoma
• Malignant fibrous histiocytoma

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What are the basics of diagnosis?
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What are the basics of diagnosis?

• Signalment
• History
• Location and progression of the lesions(s)
• Cytology/FNA
• Biopsy (histopath, bacterial fungal culture)

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23 yr Percheron Gelding
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chief complaint nodules on penis and prepuce
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Differential diagnosis?
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Differential diagnosis

• Melanomas
• Inflammatory granulomas

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Diagnostic Plan

• Fine Needle Aspirate
• Biopsy
• Abdominal palpation/ultrasound exam for evidence
  of metastasis

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Clinical Management

• Observation
• Cimetidine 5 mg/kg q 12 hrs for gt 3 months
• ? intratumoral chemotherapy with cisplatin
• ? immunotherapy with BCG

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6 yr AQHA Mare Ulcerated nodule at medial canthus
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Differential diagnosis?
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Differential diagnosis

• Inflammatory
• Habronema
• Fungal (histo, sporo)
• Post injury exuberant granulation tissue
• Neoplastic
• Sarcoid
• Squamous cell carcinoma
• Basal cell carcinoma
• Mast cell tumor

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Diagnostic Plan

• Impression smear cytology
• Biopsy
• Histopath
• Fungal bacterial culture

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Results

• Cytology
• Numerous eosinophils and macrophages
• Histopath
• Eosinophilic dermatitis with intralesional larvae

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Clinical Management

• Corticosteroids to decrease inflammation
• 600 mg pred daily x 10 days then 300 mg daily for
  another 10-14 days
• Fly mask to protect from flies
• Ivermectin orally
• Topical corticosteroid-antibiotic ointment or
  cream (ophthalmic)

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8 yr AQHA Gelding
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Differential diagnosis?
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Differential diagnosis

• Inflammatory
• Habronema
• Fungal (histo, sporo)
• Post injury exuberant granulation tissue
• Neoplastic
• Sarcoid
• Squamous cell carcinoma
• Basal cell carcinoma
• Mast cell tumor

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Diagnostic Plan

• Impression smear cytology
• Biopsy
• Histopath
• Fungal bacterial culture

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Fibroblastic Sarcoid

• Probable viral etiology (related to bovine
  papillomaviruses)
• Types
• Verrucous (wart-like)
• Fibroblastic (proud flesh-like)
• Mixed
• Occult (flat)

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Management Options

• Cyrosurgery
• CO2 Laser Surgery
• Intralesional cisplatin
• Intralesional BCG
• Topical Imiquimod (Aldara)
• Topical XXTERRA (bloodroot ZnCl)

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14 yr Paso Fino Mare
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Presenting Complaint

• Inspiratory stridor
• Mass in right nostril
• Also has partial alopecia over withers and
  thickening of skin in that region

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Differential diagnosis?
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Differential diagnosis

• Inflammatory
• Bacterial infections
• Fungal infections
• Amyloidosis
• Neoplastic
• Lymphosarcoma
• Fibroma/fibrosarcoma
• Mast cell tumors

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Diagnostic Plan

• Impression smears/FNA
• Biopsies
• Histopath
• Bacterial Fungal Cultures

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Amyloidosis

• May be primary or secondary to chronic infections
• Primary is most likely when the skin and upper
  respiratory tract are affected
• Fibrils are composed of AL amyloid (monoclonal
  immunoglobulin light chains)

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Amyloidosis Clinical Management

• Treat secondary infections
• Surgical excision of nodules interfering with
  respiration
• ? Topical DMSO (may promote amyloid degradation)

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10 yr AQHA gelding
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Differential Diagnoses?
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Differential Diagnoses

• Inflammatory
• Bacterial granulomas
• Dermatophyte kerions
• Warbles
• Tick bite granulomas
• Erythema multiforme
• Dermoid/follicular cysts
• Eosinophilic granulomas
• Collagenolytic granulomas
• Panniculitis

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Differential Diagnoses

• Neoplastic
• Basal cell tumors
• Hair follicle tumors
• Mast cell tumors

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Diagnostic Plan

• FNA
• Biopsy
• Histopath
• Bacterial fungal cultures

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Histopath

• Multiple foci of collagenolysis
• Inflammatory infiltrate is predominantly
  eosinophilic
• No larval fragments

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Collagenolytic Granulomas/Eosinophilic Granulomas

• Most common in spring summer
• Most common on back, withers and neck
• Not painful or pruritic
• Likely a consequence of fly or mosquito bites

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Clinical Management

• Observation
• Surgical excision
• Sublesional injections of triamcinolone acetonide
  (3-5 mg/lesion) repeated q 2 wks for max of 3
  times
• Fly mosquito control (fly sheets/repellants)

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24 yr AQHA gelding
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Differential Diagnosis?
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Differential Diagnoses

• Inflammatory
• Bacterial granulomas (dermatophilosis)
• Dermatophyte kerions
• Warbles
• Tick bite granulomas
• Erythema multiforme
• Dermoid/follicular cysts
• Eosinophilic granulomas
• Collagenolytic granulomas
• Panniculitis

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Differential Diagnoses

• Neoplastic
• Basal cell tumors
• Hair follicle tumors
• Mast cell tumors
• Sarcoids

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Diagnostic plan

• Impression smears/FNA
• Biopsies
• histopathology
• Fungal and bacterial culture

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Cytology
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Dermatophilosis Clinical Management

• Keep dry
• Remove crusts (2-4 chlorhexidine shampoo)
• Chlorhexidine cream or spray daily
• If does not resolve with topical treatment
  systemic penicillin or oral TMS until lesions
  resolve

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12 yr Clydesdale gelding
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Differential Diagnosis?
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Differential Diagnoses

• Inflammatory
• Bacterial granulomas
• Fungal granulomas/dermatophyte kerions
• Tick bite granulomas
• Eosinophilic/collagenolytic granulomas

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Differential Diagnoses

• Neoplastic
• melanocytomas
• lymphosarcoma
• Basal cell tumors
• Hair follicle tumors
• Mast cell tumors

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Diagnostic Plan

• Cytology/FNA
• Biopsies
• Histopathology
• Bacterial and fungal cultures

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Sporotrichosis

• Iodides
• NaI 20-40 mg/kg IV for 2-5 days then orally until
  cured
• KI 1-2 mg/kg PO daily for 1 wk then 0.5-1 mg/kg
  daily until cured
• Iodism scaling, alopecia, depression, anorexia,
  lacrimation, salivation
• Itraconazole
• 5 mg/kg PO daily

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9 yr TB mare
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Differential Diagnoses?
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Differential Diagnoses

• Inflammatory
• Infectious bacterial, fungal, parasitic,
  pythiosis
• Post traumaticexuberant granulation tissue
• Parasitichabronema, hypoderma
• Neoplastic
• Squamous cell, sarcoid, mast cell tumor,
  malignant fibrous histiocytoma

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Diagnostic Plan

• Cytology
• Biopsy
• Histopathology
• Bacterial fungal cultures

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Fistulous Withers

• Inflammation of the supraspinous bursae
• Ruptures and drains a clear or purulent fluid
• Occasionally associated with Brucella abortus or
  occasionally B suis infection
• Run an agglutination titer for Brucella

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Fistulous withers clinical management

• Surgical debridement (remove infected bursa)
• Systemic antibiotics based on CS
• ?? Vaccinate with strain 19 brucella SQ or IV ??

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4 yr old Belgian gelding
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Differential diagnoses?
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Differential Diagnoses

• Inflammatory
• Bacterial (especially Corynebacterium
  pseudotuberculosis)
• Fungal (especially Basidiobolomycosis)
• Pythiosis
• Exuberant granulation tissue
• Neoplastic
• Fibroma/fibrosarcoma
• Sarcoid
• Squamous cell carcinoma

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Diagnostic Plan

• Cytology
• Biopsy
• Histopathology
• Bacterial fungal cultures

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Pythiosis
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Pythiosis Clinical management

• Surgical excision/debulking (laser?)
• Immunotherapy with vaccine prepared from Pythium
  hyphal extract (2 ml SQ weekly for at least 3
  treatments)
• Itraconazole Terbinafine are effective in
  20 of dogs but
• Do not allow horses to stand in ponds!

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Ventral Midline of 14 yr Tennessee Walker gelding
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Differential Diagnoses?
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Differential Diagnoses

• Horn fly hypersensitivity
• Culicoides hypersensitivity
• Dermatophilosis
• Dermatophytosis
• Pelodera dermatitis
• Onchocerciasis (? Usually dorsal)
• Contact dermatitis
• Bacterial pyoderma

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Diagnostic Plan

• Cytology
• Skin scrapings
• Biopsy
• Histopathology
• Bacterial fungal cultures
• Intradermal skin testing for hypersenstivity to
  Culicoides and Horn Flies (Haemotobia irritans)

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Results

• Eosinophilic Dermatitis
• 4 reaction to Culicoides

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Ventral Midline Dermatitis Management

• Topical corticosteroids /- antibiotics
• Protect from gnats and flies
• Check stable hygiene (remove straw bedding if
  diagnose Pelodera)

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Culicoides Preventative strategies

• Stable dusk to dawn
• Fans in stalls
• 32 mesh screens
• Insecticides and repellants
• Eliminate standing water (breeding areas for the
  gnats)

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