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Y4 SA dermatology > Draining sinus tracts 2 > Flashcards

Draining sinus tracts 2 Flashcards

Infectious causes

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Dermatology Board Prep flashcards
1
Q

Infectious causes

A
  • Bacterial
  • Subcutaneous (deep) fungal infections
  • Protozoa/parasites
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2
Q

Bacterial causes

A
  • Deep pyoderma (common)
  • Bacterial granulomatous dermatitis
    – Mycobacterial granuloma/pyogranuloma (common)
  • Non-filamentous bacterial granulomas (botryomycosis): Staphs/Streps/Actinobacilli
  • Filamentous bacterial granulomas: Nocardia/Actinomyces
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3
Q

Subcutaneous (deep) fungal infection causes

A
  • Subcutaneous dermatophytic granuloma
  • Saprophytic s/c fungal infection
  • Sporotrichosis
  • Cutaneous involvement with systemic mycoses
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4
Q

Protozoal/parasitic causes

A
  • Leishmaniasis
  • Demodicosis
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5
Q

Which layer of the skin do all infectious causes affect?

A
  • the deep skin / subcutis
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6
Q

Treatment for any deep infection

A
  • 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
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7
Q

Deep pyoderma - Which skin structures are involved?

A
  • Infection outside epidermis or hair follicle epithelium
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8
Q

Deep pyoderma - What are the potential routes of infection, and which is most common?

A

§ rupture of hair follicle wall (furunculosis) – most common
§ penetrating wounds/ foreign bodies
§ haematogenous spread (sepsis) - rare

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9
Q

Deep pyoderma - What lesions are most commonly seen?

A

§ thickening of skin/subcutaneous tissue
§ +/- nodules
§ +/- draining sinuses

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10
Q

Deep pyoderma - What are the three most common manifestation of a deep pyoderma?

A
  • Furunculosis
  • Abscess
  • Cellulitis
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11
Q

Furunculosis - How does furunculosis usually develop?

A
  • Extension of folliculitis -> rupture of hair follicle wall -> microbes + free
    keratin in dermis -> provokes a foreign-body reaction
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12
Q

Furunculosis - What type of inflammation is present? How will you recognise this on cytology?

A
  • Usually pyogranulomatous reaction
    – see macrophages, neutrophils +/- rbcs
  • NB organisms may be hard to find – do not assume is sterile
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13
Q

Furunculosis - Are the lesions always pruritic?

A
  • Lesions often painful, variably pruritic
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14
Q

Furunculosis - How do you treat bacterial furunculosis?

A
  • 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.

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15
Q

Furunculosis - Why does inflammation often persist, even after bacterial infection is resolved?

A
  • 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)
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16
Q

Clinical manifestations of furunculosis

A

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
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17
Q

What organism do deep pyoderma most commonly involve? What about furunculosis

A
  • Deep pyoderma: Staphylococcal infections
  • Furunculosis: other organisms (including gram-negative bacteria), so cytology & C&ST is essential
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18
Q

What conditions may bacterial furunculosis occur secondarily to?

A
  • 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

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19
Q

Interdigital folliculitis/furunculosis - pathogenesis

A

§ 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.

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20
Q

What condition is interdigital folliculitis/furunculosis commonly seen with?

A
  • chronic pododermatitis
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21
Q

2 most common primary causes of chronic pododermatitis in dogs

A
  • AD/AFR (atopic dermatitis / adverse food reaction)
  • Conformation
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22
Q

Predisposing causes of interdigital folliculitis/furunculosis

A

– 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?

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23
Q

Interdigital folliculitis/furunculosis - secondary causes

A
  • 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

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24
Q

Interdigital folliculitis/furunculosis - perpetuating causes

A
  • 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

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25
Q

Interdigital folliculitis/furunculosis - approach to clinical case

A

§ 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?

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26
Q

Interdigital folliculitis/furunculosis - surgery

A

§ 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

27
Q

Acral lick dermatitis/granuloma - what is it? how does it present?

A

– 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

28
Q

Acral lick dermatitis/granuloma - underlying causes

A

§ 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

29
Q

Acral lick dermatitis/granuloma - clinical features

A

§ 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

30
Q

Acral lick dermatitis/granuloma - diagnosis

A
  • 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
31
Q

Acral lick dermatitis/granuloma - general management

A
  • may need lifelong control if chronic +/or unable to correct underlying cause
32
Q

Acral lick dermatitis/granuloma - management of the mild case

A

§ Treat deep pyoderma to resolve infection
§ Investigate/control underlying disease.
- NB suspect behavioural component once medical causes ruled out

33
Q

Acral lick dermatitis/granuloma - management of the more case

A

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

34
Q

Post-grooming folliculitis/furunculosis - presentation

A

§ 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

35
Q

Post-grooming folliculitis/furunculosis - cause

A
  • minor trauma to hair follicles followed by infection when bathed
    – contaminated bathing products implicated
    -> Pseudomonas grows in home-made shampoo
36
Q

Post-grooming folliculitis/furunculosis - diagnosis

A

§ Often G-ve organisms cultured, esp Pseudomonas
§ Distinctive histopathology

37
Q

What is an abscess? Which species are they common in?

A
  • Pooling of suppurative material in dermis/subcutis
    -–usually well-defined
  • Especially common in cats
38
Q

What is cellulitis?

A
  • Ill-defined inflammation involving deep s/c connective tissue
39
Q

When should you suspect an abscess/cellulitis?

A

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

40
Q

Abscess tx

A

– lance, drain, analgesia
- Systemic antibiotics (e.g. amoxicillin-clavulanate) if cellulitis or pyrexia

Amoxiclav used as also works against gram negative

41
Q

Cellulitis tx

A

– systemic antibiotics (e.g. amoxicillin-clavulanate)
– usually empirically

Amoxiclav used as also works against gram negative

42
Q

Where are foreign bodies commonly found?

A
  • Can occur at any site but common interdigitally
    § Esp grass awns, summer, dogs with hairy feet
43
Q

FB tx

A

§ 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

44
Q

Bacterial granulomatous dermatitis - cause, presentation

A

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

45
Q

Mycobacterial infections in cats - causative agents

A
  1. Mycobacterium tuberculosis complex (MTBC) - 30% feline mycobacterial infections
  2. Non-tuberculous mycobacteria (NTM)
46
Q

MTBC - species & their zoonotic risk

A
  • 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
47
Q

MTBC - at risk cats

A
  • males
  • hunters
  • young-middle aged
  • M bovis infection in areas with bovine TB
48
Q

MTBC - association with FIV/FeLV infection / immunosuppression?

A
  • no
49
Q

MTBC - infection route

A
  • via rodent bites
  • rarely oral/inhaled infection
50
Q

NTM 4 subgroups (& infection route)

A

§ 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

51
Q

What is NTM?

A
  • Non-tuberculous mycobacteria
  • Environmental mycobacteria
    – e.g. in soil, water
52
Q

Mycobacterium leprae complex (what is causes, signalment, is it zoonotic?

A
  • -> feline leprosy syndrome (FLS)
  • especially young cats (<4yo)
  • ‘cat is ‘dead end host’ -> not zoonotic
53
Q

M avium complex (MAC) (what is causes, signalment, is it zoonotic?

A

-> most commonly isolated in UK
- especially older cats
- associated with immunosuppression
- potential zoonosis (low risk unless immunocompromised)

54
Q

Mycobacterium tuberculosis complex (MTBC) - clinical presentation

A
  • 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
55
Q

Non-tuberculosis mycobacteria (NTM) - clinical presentation

A
  • 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

56
Q

Diagnosis of bacterial granulomatous dermatitis

A

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.

57
Q

Tx of bacterial granulomatous dermatitis

A

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

58
Q

What to do if M bovis infection is diagnosed in a pet cat or dog

A

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

59
Q

Subcutaneous (deep) fungal infections - caused by:

A

§ Subcutaneous dermatophytic granuloma (ringworm under the skin)
§ Saprophytic s/c fungal infection
§ Sporotrichosis (Sporothrix schenkii) – zoonotic, especially from cats

60
Q

Subcutaneous (deep) fungal infections - present as:

A
  • 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))
61
Q

Systemic mycoses

A

Can affect any organ system, including skin
-> granulomas/pyogranulomas/necrosis in organs affected
-> systemically ill
e.g. Cryptococcosis – zoonotic

62
Q

What is panniculitis?

A
  • inflammation of the fat
63
Q

If you see a cat with multiple draining sinuses what should your top ddx be?

A
  • mycobacteria

Y4 SA dermatology (22 decks)

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