Draining sinus tracts 2 Flashcards
Infectious causes
Infectious causes
- Bacterial
- Subcutaneous (deep) fungal infections
- Protozoa/parasites
Bacterial causes
- Deep pyoderma (common)
- Bacterial granulomatous dermatitis
– Mycobacterial granuloma/pyogranuloma (common) - Non-filamentous bacterial granulomas (botryomycosis): Staphs/Streps/Actinobacilli
- Filamentous bacterial granulomas: Nocardia/Actinomyces
Subcutaneous (deep) fungal infection causes
- Subcutaneous dermatophytic granuloma
- Saprophytic s/c fungal infection
- Sporotrichosis
- Cutaneous involvement with systemic mycoses
Protozoal/parasitic causes
- Leishmaniasis
- Demodicosis
Which layer of the skin do all infectious causes affect?
- the deep skin / subcutis
Treatment for any deep infection
- Treat systemically for extended period to minimum 2 weeks post-resolution
- Antimicrobial choice usually based on culture
- +/- adjunctive topical therapy
- Avoid immunosuppressive drugs (e.g. corticosteroids)
- Consider underlying cause
Deep pyoderma - Which skin structures are involved?
- Infection outside epidermis or hair follicle epithelium
Deep pyoderma - What are the potential routes of infection, and which is most common?
§ rupture of hair follicle wall (furunculosis) – most common
§ penetrating wounds/ foreign bodies
§ haematogenous spread (sepsis) - rare
Deep pyoderma - What lesions are most commonly seen?
§ thickening of skin/subcutaneous tissue
§ +/- nodules
§ +/- draining sinuses
Deep pyoderma - What are the three most common manifestation of a deep pyoderma?
- Furunculosis
- Abscess
- Cellulitis
Furunculosis - How does furunculosis usually develop?
- Extension of folliculitis -> rupture of hair follicle wall -> microbes + free
keratin in dermis -> provokes a foreign-body reaction
Furunculosis - What type of inflammation is present? How will you recognise this on cytology?
- Usually pyogranulomatous reaction
– see macrophages, neutrophils +/- rbcs - NB organisms may be hard to find – do not assume is sterile
Furunculosis - Are the lesions always pruritic?
- Lesions often painful, variably pruritic
Furunculosis - How do you treat bacterial furunculosis?
- Usually require extended systemic antibiotic course based on C&ST (culture of tissue or exudate)
– Continue to 2 weeks post-resolution (minimum 4 weeks, often 6-8+ weeks total) - Topical chlorhexidine shampoos/foams also
Can have occasional cases where its sterile and would treat with steroids. But otherwise treat with antibiotics based on culture.
Furunculosis - Why does inflammation often persist, even after bacterial infection is resolved?
- Inflammation may persist after infection resolved due to foreign body reaction to keratin – at this stage may therefore need anti-inflammatory medication (corticosteroids/ ciclosporin/ tacrolimus)
Clinical manifestations of furunculosis
Furunculosis may occur at any site but there are several specific presentations:
- Chin/muzzle folliculitis/furunculosis
– ‘Canine acne’ particularly in young dogs - Nasal folliculitis/furunculosis
– Affects haired skin of dorsal muzzle
– d/d canine eosinophilic folliculitis/furunculosis
-> cytology + biopsy - Interdigital folliculitis/furunculosis
- Acral lick dermatitis/granuloma
- Post-grooming folliculitis/furunculosis
- German Shepherd Dog pyoderma (rare)
– Widespread severe furunculosis/cellulitis
– Underlying cause poorly understood
– Seen particularly along the trunk
– More common historically
What organism do deep pyoderma most commonly involve? What about furunculosis
- Deep pyoderma: Staphylococcal infections
- Furunculosis: other organisms (including gram-negative bacteria), so cytology & C&ST is essential
What conditions may bacterial furunculosis occur secondarily to?
- Allergies
- Ectoparasites – NB demodicosis
- Infections – NB dermatophytosis
- Systemic immunosuppression/endocrinopathy
- Pressure driving hair back into skin, e.g.
– Over bony prominences of heavy short-coated dogs
– Conformation defects causing dog to walk on haired skin
NB demodicosis and dermatophytosis both also cause folliculitis
Interdigital folliculitis/furunculosis - pathogenesis
§ Multifactorial pathogenesis
§ Starts as sterile process but become infected when lesions rupture and are licked
§ NB Lesions originate on palmo-plantar surface of foot but rupture as draining sinus tracts on dorsal aspect
Some sort of pathology to the underside of the foot that causes thickening of the skin. Thickening of the skin means hair follicles can’t drain, cysts form, go up the skin and burst within the web, FB reaction to it, sinus open up on the dorsal aspect of the web.
What condition is interdigital folliculitis/furunculosis commonly seen with?
- chronic pododermatitis
2 most common primary causes of chronic pododermatitis in dogs
- AD/AFR (atopic dermatitis / adverse food reaction)
- Conformation
Predisposing causes of interdigital folliculitis/furunculosis
– Breed
* Includes EBD, FBD, Mastiff-types
* Short hairs around pad margins/ interdigital skin
* Often with splayed feet and poor conformation
– Increased weight-bearing
* Fore > hind
* Obesity
– Altered weight-bearing (that cause weight bearing on haired skin)
* Congenital limb deformity
* OA
* Cruciate disease/other joint problems
* Restrictive harnesses?
Interdigital folliculitis/furunculosis - secondary causes
- secondary causes -> secondary infections
- Surface/superficial/ deep infections
– Potentially multiple infections at different depths, esp if chronic, e.g.
§ Staph pseudintermedius
§ Streptococcus spp
§ E coli/ Klebsiella spp/ Pseudomonas spp
§ Malassezia
NB If primary cause not addressed -> recurrent bacterial infections (+/- fungal) -> antibiotic resistance
Interdigital folliculitis/furunculosis - perpetuating causes
- Altered weight-bearing
- Weight-bearing on haired skin
- Lichenification/scarring
- Chronic inflammation
All ^ lead to a self-perpetuating cycle of increasing inflammation and abnormal pedal conformation, which leads to:
- Conjoined pads/new pad formation In-grown hairs
- Sinus tracts
- Deep tissue pockets
All ^ which:
- Trap debris
- Encourage infection
- Prevent effective cleaning/Tx
Interdigital folliculitis/furunculosis - approach to clinical case
§ Consider primary cause – NB always rule out demodicosis. Other investigations/treatment as
indicated
§ Investigate and treat secondary infections
§ Control inflammation once infection controlled
– GCCs – topical/systemic
– Ciclosporin/ 0.1% tacrolimus
– Not oclacitinib / lokivetmab
§ Address predisposing triggers, where possible
– e.g. reduce weight, analgesia if underlying pain, corrective surgery re conformation?, boots at exercise to protect feet?
Interdigital folliculitis/furunculosis - surgery
§ For end-stage disease, refractory to medical management
§ Excision or fusion podoplasty
§ Scalpel or laser surgery – essential to remove all diseased tissue
§ Recurrence less likely with laser podoplasty, as all diseased tissue ablated and replaced with scar tissue
Acral lick dermatitis/granuloma - what is it? how does it present?
– a deep pyoderma but does not present with sinus tracts
– a d/d for cutaneous masses
- Localised folliculitis/furunculosis on lower limbs due to self trauma
Acral lick dermatitis/granuloma - underlying causes
§ Pruritus - allergies, ectoparasites
§ Pain – small injury/ underlying orthopaedic/neurologic disorder
§ Neoplasia - uncommon
§ Anxiety/boredom – causes +/or exacerbates?
NB several factors may coexist – all need to be addressed
Acral lick dermatitis/granuloma - clinical features
§ Usually large breed, middle-aged/older dogs
§ Lesions
– Plaque-like, firm +/- ulceration
– Often hyperpigmented, lichenified rim
– Often forelimbs
– Can look slightly like a crater
§ Initial deep infection but, with chronicity, can develop
– ongoing inflammation/pruritus due to FB reaction to intradermal keratin
– obsessive-compulsive behavioural component
Acral lick dermatitis/granuloma - diagnosis
- Often visually distinctive, especially when small
- Cytology (squeeze lesion) and deep bacterial culture ideal
- Biopsies if unsure re diagnosis – d/d neoplasia, deep fungal infection
- Careful history/clinical exam re establishing underlying cause essential
Acral lick dermatitis/granuloma - general management
- may need lifelong control if chronic +/or unable to correct underlying cause
Acral lick dermatitis/granuloma - management of the mild case
§ Treat deep pyoderma to resolve infection
§ Investigate/control underlying disease.
- NB suspect behavioural component once medical causes ruled out
Acral lick dermatitis/granuloma - management of the more case
Treat deep pyoderma to resolve infection
Physical prevention of licking – E-collars, wrap, sock, ?muzzle
Control inflammation once infection controlled: topical/systemic GCCs, ciclosporin/ 0.1% tacrolimus
Behavioural modification +/or behaviour-modifying drugs? (e.g. clomipramine, fluoxetine) – behavioural referral?
Laser surgery for recalcitrant lesions? – NB
* Lack of free skin hampers wound closure for sharp surgery
* Surgical site may become new focus for licking
Post-grooming folliculitis/furunculosis - presentation
§ Uncommon but distinctive furunculosis of dorsal trunk
§ History important for diagnosis: Acute onset within few days of bathing/traumatic grooming procedure. Skin lesions may be preceded by fever, depression
§ Very painful – d/d back pain
Post-grooming folliculitis/furunculosis - cause
- minor trauma to hair follicles followed by infection when bathed
– contaminated bathing products implicated
-> Pseudomonas grows in home-made shampoo
Post-grooming folliculitis/furunculosis - diagnosis
§ Often G-ve organisms cultured, esp Pseudomonas
§ Distinctive histopathology
What is an abscess? Which species are they common in?
- Pooling of suppurative material in dermis/subcutis
-–usually well-defined - Especially common in cats
What is cellulitis?
- Ill-defined inflammation involving deep s/c connective tissue
When should you suspect an abscess/cellulitis?
Suspect on basis of
* History/signalment, e.g.
– outdoor cat (bite wounds)
– dog with hairy feet in summer (grass seed)
* Clinical examination
– Painful swelling, usually solitary lesions
– Evidence of wound? (NB bite wounds often in pairs!)
– +/- pyrexia, lethargy
* FNA abscess – gross appearance usually diagnostic – cytology to check if any doubt
Abscess tx
– lance, drain, analgesia
- Systemic antibiotics (e.g. amoxicillin-clavulanate) if cellulitis or pyrexia
Amoxiclav used as also works against gram negative
Cellulitis tx
– systemic antibiotics (e.g. amoxicillin-clavulanate)
– usually empirically
Amoxiclav used as also works against gram negative
Where are foreign bodies commonly found?
- Can occur at any site but common interdigitally
§ Esp grass awns, summer, dogs with hairy feet
FB tx
§ Poultice/bathe to‘draw’, then explore carefully UGA with alligator forceps -> remove FB
§ Can track up limb – possible use of contrast radiography +/or US
§ Avoid antibiotics till explored
NB Usually solitary lesions, though occasionally contain >1 FB – check
Bacterial granulomatous dermatitis - cause, presentation
Caused by traumatic implantation of saprophytic organisms
a. Mycobacterial granulomas/ pyogranulomas
b. Non-filamentous bacterial granulomas - rare
- e.g. Staphylococci, Streptococci, Actinobacillus
- Also called botryomycosis
- Lesions contain small yellow granules (‘sulphur’ granules)
c. Filamentous bacterial granulomas - rare
- e.g. Nocardia, Actinomyces
- -> nodular masses which may involve bone
- affect dogs/cats
Mycobacterial infections in cats - causative agents
- Mycobacterium tuberculosis complex (MTBC) - 30% feline mycobacterial infections
- Non-tuberculous mycobacteria (NTM)
MTBC - species & their zoonotic risk
- M microti (rodent-adapted)
- *M bovis (cattle adapted)
M microti & bovis are most common in cats – regional distributions; low zoonotic risk
**M tuberculosis (human-adapted) – rare - cats relatively resistant; significant zoonotic risk -> euthanasia
- NOTIFIABLE ANIMAL disease–contact APHA
** NOTIFIABLE human disease – contact UK Health Security Agency
MTBC - at risk cats
- males
- hunters
- young-middle aged
- M bovis infection in areas with bovine TB
MTBC - association with FIV/FeLV infection / immunosuppression?
- no
MTBC - infection route
- via rodent bites
- rarely oral/inhaled infection
NTM 4 subgroups (& infection route)
§ Mycobacterium leprae complex (MLC)
§ M avium complex (MAC)
§ Slow-growing NTM
§ Rapid-growing NTM (e.g. M fortuitum, M chelonae)
All opportunist pathogens – infect cats via contamination of open wounds
What is NTM?
- Non-tuberculous mycobacteria
- Environmental mycobacteria
– e.g. in soil, water
Mycobacterium leprae complex (what is causes, signalment, is it zoonotic?
- -> feline leprosy syndrome (FLS)
- especially young cats (<4yo)
- ‘cat is ‘dead end host’ -> not zoonotic
M avium complex (MAC) (what is causes, signalment, is it zoonotic?
-> most commonly isolated in UK
- especially older cats
- associated with immunosuppression
- potential zoonosis (low risk unless immunocompromised)
Mycobacterium tuberculosis complex (MTBC) - clinical presentation
- Localised cutaneous nodules +/- ulcers/draining tracts, especially ‘fight and flight’ sites – face, extremities, tail base
- +/- localised/generalised lymphadenopathy
- +/- GI disease, lung disease, weight loss, pyrexia
Non-tuberculosis mycobacteria (NTM) - clinical presentation
- Cutaneous or s/c nodules – as MTBC
- Diffuse panniculitis – multiple punctate draining tracts and
s/c nodules, esp inguinum, flanks, tailbase – may coalesce - Variably painful
- Disseminated disease uncommon
NB Feline leprosy syndrome – non-painful, mobile cutaneous nodules only
Diagnosis of bacterial granulomatous dermatitis
NB take rigorous hygiene precautions re infection/contamination
Biopsy
§ Biopsy any non-resolving skin lesions/abscesses/ enlarged peripheral
lymph-nodes! Ensure to include subcutis, multiple samples
§ Bisect – half for histology (request Ziehl-Neelsen (ZN) stain – 50%
sensitivity), half to freeze for future tests
§ Wedge not punch biopsy to get to the subcutis.
Cytology
§ Granulomatous/pyogranulomatous response (mixed inflammatory cells).
May see organisms with ZN stain but low sensitivity
Culture
§ Gold standard but need special laboratories, culture slow (e.g. 3 months) and fails 50% of time, even when ZN +ve organisms seen
IFN-gamma-release assay (IGRA) on blood
– quicker
–sensitivity variable
– distinguishes between NTMs only
PCR
– fixed or fresh tissue
- Not 100% sensitive
Once diagnosis made -> screen for immunosuppressive factors and thoracic radiography – assess lung involvement
NB cannot speciate organisms, even if seen on biopsy or cytology.
Tx of bacterial granulomatous dermatitis
Treatment complex - consult experts/current literature when needed
Antibiotics
§ Need long courses (e.g. 6+ months), based on C+S where possible – some need permanent tx to prevent relapse. Resistance can develop.
§ Usually combination therapy of 2 or 3 drugs required – e.g. empirical fluoroquinolone + doxycycline + clarithromycin for NTM pending sensitivity results
§ Can be controversial as some drugs restricted, e.g. rifampicin
§ Continue antimicrobial therapy for 2 months post-resolution – prognosis guarded
Wide surgical resection where possible – likely curative for FLS
What to do if M bovis infection is diagnosed in a pet cat or dog
Vet must notify APHA who will
§ notify UK Health Security Agency -> assess if TB screening of close contact people needed
§ consider risks to nearby animals
-. Develop plan to protect other pets/livestock, if necessary
-> Advise if TB testing required for livestock on premises
Euthanasia of affected pet, although not mandatory, may be elected due to concerns re
§ Treatment length (6mo+) and need for concurrent use of multiple drugs -> compliance issues
§ AMR concerns (course length, potential use of restricted antibiotics)
§ Guarded prognosis – often do not recover fully
§ Zoonosis (low risk) and contagion
Subcutaneous (deep) fungal infections - caused by:
§ Subcutaneous dermatophytic granuloma (ringworm under the skin)
§ Saprophytic s/c fungal infection
§ Sporotrichosis (Sporothrix schenkii) – zoonotic, especially from cats
Subcutaneous (deep) fungal infections - present as:
- cutaneous papules or s/c nodules
- +/- ulceration/discharging tracts/tissue
- +/- tissue granules/grains (i.e. gritty feeling under the skin)
- Usually due to traumatic implantation of fungus - most commonly on feet/limbs or head
- Regional lymphadenopathy common
- Occasionally disseminate to other organs
- Check underlying health (e.g. FeLV/FIV (cats) thyroid (dogs))
Systemic mycoses
Can affect any organ system, including skin
-> granulomas/pyogranulomas/necrosis in organs affected
-> systemically ill
e.g. Cryptococcosis – zoonotic
What is panniculitis?
- inflammation of the fat
If you see a cat with multiple draining sinuses what should your top ddx be?
- mycobacteria
