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11 Cards in this Set

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What diagnostic plan would be useful for skin lesions characterised by nodules, sinuses or non-healing wounds?
1 Full general and dermatological Hx

2 PE and dermatological exam

3 Problem list

4 Cytology of primary lesions, exudates, aspirates and regional lymph nodes.
Inform the laboratory that an unusual organism is suspected
5 Biopsy for histopathology
o multiple specimens, do not prep the site
o ideally a wedge incorporating normal tissue and fully developed lesion
o request special stains
Biopsy for culture and sensitivity
o surgically prep the site and collect deep tissue aseptically
o ideally sample open and closed lesions
o request aerobic and anaerobic bacterial culture and fungal culture

6 Screen for systemic illness:
• Blood and urine for CBC, biochemistry, urinalysis +/- serology eg LCAT.
• Consider diagnostic imaging
What are some differentials for skin lesions characterised by nodules, sinuses or non healing
• Bacterial
o Actinomycoses, Nocardiosis, pseudomycetoma
o Mycobacteriosis, leproid granuloma
• Fungal
o Aspergillosis (blastomycosis, histoplasmosis, coccidiomycosis)
o Cryptococcosis
o Dermatophytosis
o Opportunist fungal infections
• Algal
o protothecosis
• Parasitic
o Leishmaniasis
o Neosporosis
o Sarcocystosis
o Parasitic larvae: dirofilariasis, habronemiasis
• Non-infectious, inflammatory
o foreign body
o sterile nodular panniculitis
o eosinophilic granuloma
o sterile granuloma/ pyogranuloma syndrome
o reactive histiocytosis
• Neoplastic
o malignant histiocytosis
o mast cell tumour
o perianal sebaceous adenoma/ carcinoma
o lipoma
o sebaceous adenoma/ hyperplasia
o squamous cell carcinoma
o melanoma
o fibrosarcoma
o basal cell tumour
o haemangioma, haemangiosarcoma
The lesions in this picture are caused by Actinomycosis. What are some clinical features associated with this disease and how would you diagnose and treat it?
Chronic, pyogranulomatous disease of dogs and cats

Actinomycetaceae are saprophytes of mucous membranes. Not normally pathogenic, but cause disease if innoculated into tissue

Dog: nodules and sinuses in the skin and subcutis of the face, +/- osteomyelitis,
pneumonia, mediastinitis, pyothorax and pleuritis, pericardial effusion, abdominal masses and peritoneal effusion, retroperitoneal masses and effusions +/- vertebral osteomyelitis
cutaneous masses and draining sinuses

Cat: pyothorax and subcutanous bite wound abscesses.
Dx: lesions suppurative to pyogranulomatous
“Sulphur granules” may be visible macroscopically
need to collect anaerobically and request special culture
Histopathology: core of neutrophils and organisms surrounded by dense granulation tissue

Tx: prolonged penicillin G or V & surgical debridement, irrigation and search for FB
Which common soil saphrophyte could be the causative organism for this lesion?
What CS are associated with the resulting disease and how would you proceed to diagnose and treat?
Nocardiaceae: Gram positive, partially acid fast filamentous bacteria, opportunistic pathogen esp. immunocompromised patients

uncommon in dogs, typically pulmonary (bronchopneumonia/mass lesions/pleural effusion), disseminated (with concuttent pulmonary infection)
or cutaneous/subcutaneous -> firm to fluctuant swellings that
may ulcerate or develop fistulous tracts with reddish-brown exudate +/- sulphur granules

Feline nocardiosis occurs in the same three forms as dogs but most commonly as
cutaneous/subcutaneous abscesses or mycetomas
Dx: cytology-> suppurative to pyogranulomatous inflammation, C&S

Tx: sulphonamides so sulphonamide-trimethoprim is DoC 1-3m for skin lesions, up to 12m if disseminated or immuno compromised patient
Lesions should be debrided, drained and lavaged
Which 2 important syndromes are associated with cutaneous mycobacterial infections?
• canine feline leprosy (leproid granuloma) and
• mycobacterial panniculitis
What do you know about canine and feline leproid granuloma?
Single to multiple small (<4 mm) painless, raised, fleshy nodules occurring on pinnae, limbs and head

Dogs infected with MAC acquire a subclinical, progressive granulomatous disease of bowel, spleen, liver and mesenteric lymph nodes
Dx: Cytology, histopathology with acid-fast/ ZN staining

Tx: Many cases are self-limiting with 3 months. Some progress >disfigurement.
Surgical excision may be curative.
rifampin plus clarithromycin or doxycycine may be
used in severe or refractory cases
What is mycobacterial panniculitis?
chronic infection of subcutis and skin with rapidly growing
saprophytic mycobacteria RGM. Infection typically requires host immunocompromise and can result in mycobacterial panniculitis,
pyogranulomatous pneumonia or disseminated disease

Routine surgical debridement and empirical antibiotic therapy typically results in wound breakdown with development of a non-healing suppurative
tract surrounded by granulation tissue.
Dx: appropriately stained cytology of exudate or deep tissue
specimens in conjunction with culture.

Tx: sensitivity essential, commence empirical therapy with high
doses of doxycycline or cyprofloxacin initially whilst MC&S pending
continue for 3-6 months and 1-2 months after clinical remission
What disease is caused by the organism in this picture?
nodules or non-healing wounds +/- draining tracts
ZOONOTIC dimorphic fungus: mycelium at environmental temperatures and a yeast at body temperature. ubiquitous in soi l-> infection is by direct innoculation from thorns, splinters or contaminated claws
Dx: cytology, culture of deep exudate or tissue

Tx: dogs: potassium iodide
cats: itraconazole
corticosteroids contraindicated
Which systemic mycosis is associated with dermatological signs in Australia?
Cryptococus neoformans

disease in immunocompromised patients, eg. FIV

CS: upper respiratory with sneezing, snuffling, stertor, nasal discharge, a visible granulomatous polyp and/or swellling over the bridge of the nose.
Cutaneous lesions elsewhere are characterised by multiple papules or nodules that may ulcerate, on face, pinnae and paws may have CNS and occular involvement
Dx: nasal exudate, BAL, CSF, aqueous/vitreous, or FNA of nodules or enlarged lymph nodes. Stain with New Methylene Blue, Diff Quik or Gram to demonstrate the large unstained capsule. C&S

Tx: amphotericin B for severe or neurologicaldisease; itraconazole, fluconazole,
This uncommon, oedematous, vesicopustular dermatitis primarily affects the skin around the mouth, eyes and pinnae of puppies
Canine juvenile cellulitis
non-infectious, mutiple granulomatous or pyogranulomatous lesions
What describes the term panniculitis? How would you diagnose a nodular panniculitis?
general term for inflammation of subcutaneous fat
single or multiple subcutaneous nodules, localised or generalised, up to several
cm in diameter. Nodules may be firm or fluctuant and may ulcerate or exhibit draining tracts with oily to haemorrhagic exudate.
Dx of exclusion