Nodules (Marsella)

Question 1

Nodules

Answer 1

Solid elevations that extend deep into the dermal or subcutaneous tissue (inflammatory or neoplastic)

Question 2

DDX for nodules: Fungal

Answer 2

• Cryptococcus
• Histoplasma
• Coccidiodomycosis
• Sporotrichosis
• Kerion
• Mycetoma/pseudomycetoma
• Phaeohyphomycosis
• Oomyces (pythiosis)

Question 3

DDX for nodules: Bacterial

Answer 3

• Deep pyoderma
• Acral lick dermatitis
• Cutaneous bacteral granuloma
• Botryomycosis
• Abscess
• Staphylococcus furunculosis
• Opportunistic/atypical mycobacteria
• Actinomyces
• Actinobacillus
• Leprosy

Question 4

DDX for nodules: non-infectious/sterile

Answer 4

• Allergy (cats)
  
  • Eosinophilic granuloma
  • Mosquito hypersensitivity
• Sterile nodular panniculitis
• Sterile nodular granuloma/pyogranuloma
• Plasma cell pododermatitis (cats)
• Neoplastic

Question 5

Nodule diagnostic approach

Answer 5

• FNA
• Biopsy for histopath & culture
• R/O other infectious causes

Question 6

Systemic fungal infections

Answer 6

• Cryptococcosis
• Histoplasmosis
• Blastomycosis
• Coccidiodomycosis

Question 7

Subcutaneous fungal infections

Answer 7

• Sporotrichosis
• Phaeohyphomycosis
• Mycetoma
• Kerion

Question 8

Sporotrichosis (general info)

Answer 8

• Sporothrix schenckii
• Thermally dipmorphic (yeast in tissues)
• In soils and decaying organic matter
• Spread by inoculation (contaminate wound) or inhalation (rare)
• ZOONOTIC

Question 9

Infection of sporotrichosis from cats (to humans)

Answer 9

• Large number of organisms in feline exudate
• No immune suppression necessary
• Wear gloves
• Wash hands in chlorohexidine and povidone iodine

Question 10

Feline sporotrichosis

Answer 10

• Draining nodules (head, distal limb, tail)
• Hx of poor response to abx
• Autoinoculation in other parts by grooming
• Most cats develop disseminated dz

Question 11

Sporotrichosis diagnosis

Answer 11

Easiery in cats due to large number of organisms

• Cytology
• Culture
• Histopath

Question 12

Sporotrichosis treatment

Answer 12

• Itraconazole
• Ketoconazole
• Iodides
• Treat at least 1 month past resolution of clinical signs

Question 13

Iodism

Answer 13

• Oral iodine treatment not tolerated well
• Vomit, anorexia, depression
• Twitching, hypothermia
• Ocular & nasal discharge
• Dry coat, excessive scaling

Question 14

Kerion

Answer 14

• Exudative nodular lesions
• Reaction to dermatophytic infection
  
  • M. gypseum
  • T. mentagrophytes
  • Furunculosis

(Dermatophytes don’t like to be in dermis, usually die and act as foreign body)

Question 15

Dermatophytic psuedomycetoma

Answer 15

• Subcutaneous nodules
• Most common on trunk
• Frequent ulceration
• M. canis
• Persian cats
• Histopath - pyogranulomatous dermatitis w/ fungal hyphae, tissue grains

Question 16

Pythiosis (general info)

Answer 16

• “Swamp cancer” (not actual cancer)
• Fungus/algae-like oomycete
• Plant parasite
• Subtopical/tropical areas
• Infection by contact w/ contaminated water

Question 17

Pythiosis affects what species?

Answer 17

• Humans
• Dogs (esp. german shepherds, golden retrievers)
• Horses (not as aggressive as in dogs)
• Cattle

Question 18

Pythiosis clinical signs

Answer 18

• Rapidly developing nodules & draining tracts
• Intense pruritis

Question 19

Pythiosis diagnosis

Answer 19

• Cytology - eosinophils, rarely hyphae
• Biopsy
  
  • Histopath
    
    • Nodular to diffuse pyogranulomatous dermatitis
    • “Ghost” hyphae (hard to see)
  • Culture
  • Immunohistochem

Question 20

Pythiosis treatment

Answer 20

• 100% mortality w/ out treatment
• Response dependent on age of lesions
• WIDE surgical excision
• Treat 2º bacterial infections
• Amphotericin B
• Itraconazole (synergistic w/ doxy)
• Terbinafine
• Hyperbaric chamber
• Vaccine changes immune response, not preventative

Question 21

Lagenidiosis

Answer 21

• Oomyces
• Infeciton occurs by contact w/ contaminated water
• Nodules & draining tracts

Question 22

Zygomycosis

Answer 22

• Caused by fast growing, sapropytic fungi
• Wound contamination
• Nodular lesions (pyogranulomatous dermatitis & panniculitis)
• Clinically indistinguishable from pythiosis
• Poor prognosis

Question 23

Deep pyoderma

Answer 23

• Furuncolosis
• Panniculitis
• Diagnos by clinical signs, cytology, biopsy
• Tx 2-3 mos of systemic abx
• ID & corrent underlying dz

Question 24

Acral lick dermatitis presentation

Answer 24

• Raised, ulcerated mass usually on extremities
• Caused by or worsened by licking
• Incr. incidence in large breeds
• Furunculosis
• Associated w/ 2º infections

Question 25

Possible underlying causes of acral lick dermatitis

Answer 25

* Demodex * Dermatophytes * Allergies (fleas) * Hypothryroidism * Pain

Question 26

Acral lick dermatitis diagnosis

Answer 26

* Skin scrape * Fungal culture * Biopsy - histopath, culture * R/O pythium

Question 27

Acral lick dermatitis treatment

Answer 27

* Abx for 6+ wks * Tx underlying cause * Mechanical devices * Topicals * Hycodan (narcotic) * Naltrexone (narcotic antagonist) * Behavior modification * Acupuncture * Cryosurgery * Guarded long term prognosis

Question 28

Opportunistic mycobacteria

Answer 28

* Non-healing wounds * Chronic ulcers * Draining tracts * Lesions in cats often in ventral fat pads

Question 29

Diagnosis of mycobacteria

Answer 29

* Cytology (very few organisms) * Biopsy - histopath, culture (may still be false negative)

Question 30

Mycobacteria treatment

Answer 30

* Specific sensitivity testing * Fluoroquinolones * Doxycycline * Clarithromycin

Question 31

Nocardia

Answer 31

* Mimic mycobacteria, but animal is sick, anorexic * Culture * Tx w/ * penicillin and sulfa * Na iodide * Guarded prognosis

Question 32

Sterile nodular panniculitis

Answer 32

* Uncommon * Nodules w/ discharge * Systemic signs * Combo of foreign body & hypersensitivity * Associated w/ vax & injections * Dachshunds, collies, GSD predisposed * R/O infection

Question 33

Sterile pyogranulomas

Answer 33

* Rare * Typically solitary lesions, frequently on head * R/O infectious causes * Immunomodulation successful in some cases