Draining sinus tracts

• How does furunculosis usually develop?

  Extension of folliculitis -> rupture of hair follicle wall -> microbes + free keratin in dermis -> provokes a foreign-body reaction
• What type of inflammation is present in furunculosis?

  Usually pyogranulomatous reaction - see macrophages, neutrophils +/- rbcs - NB organisms may be hard to find - do not assume is sterile.
• Are the lesions of furunculosis always pruritic?

  Lesions often painful, variably pruritic.
• How do you treat furunculosis?

  Usually require extended systemic antibiotic course based on culture + susceptibility testing (culture of tissue (ideally) or exudate). Continue to 2 weeks post-resolution (minimun 4 weeks, often 6-8 weeks total).

  Topical chlorhexidine shampoos/foams also.
• What are the clinical manifestations of furunculosis?

  Chin/muzzle folliculitis/furunculosis

  Nasal folliculitis/furunculosis

  Interdigital folliculitis/furunculosis

  Acral lick dermatitis/granuloma.

  Post-grooming folliculitis/furunculosis

  GSD pyoderma (rare)
• What are the diagnostic considerations for furunculosis?

  Allergies

  Ectoparasites - NB demodicosis

  Infections - NB Dermatophytosis

  Systemic immunosuppression/endocrinopathy

  Pressure driving hair back into skin
• Interdigital folliculitis/furunculosis

  Very common in bulldogs.

  Chronic pododermatitis with interdigital folliculitis/furunculosis - common and complex problem.

  Multifactorial pathogenesis - starts as sterile process but become infected when lesions rupture and are licked.
• What are the primary causes of interdigital folliculitis/furunculosis?

  AD/AFR

  Conformation
• What are the predisposing interdigital folliculitis/furunculosis?

  Breed - includes EBD, FBD and mastiff types.

  Increased weight-bearing - fore more than the hindlimb.

  Altered weight-bearing

  • Congenital limb deformity
  • OA
  • Cruciate disease/other joint problems
  • Restrictive harnesses?
• How do you treat interdigital folliculitis/furunculosis?

  Consider primary cause - NB always rule out demodicosis/ 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:

  • Reduce weight, analgesia if underlying pain, corrective surgery
• What is Acral lick dermatitis/granuloma?

  A deep pyoderma that does not present with sinus tracts - a d/d for cutaneous masses.

  Localised folliculitis/furunculosis on lower limbs due to self-trauma.
• What are the underlying causes of Acral lick dermatitis/granuloma?

  Pruritus - allergies, Ectoparasites.

  Pain - small injury/ underlying orthopaedic/ neurological disorder.

  Neoplasia - uncommon.

  Anxiety/boredom.
• What are the clinical signs of Acral lick dermatitis/granuloma?

  Usually large breed, middle-aged/ older dogs.

  Lesions

  • Plaque-like, firm +/- ulceration
  • Often hyperpigmented, lichenified.
  • Often forelimbs

  Initial deep infection but, with chronicity, can develo:

  • Ongoing inflammation/pruritus due to FB reaction to intradermal keratin.
  • Obsessive-compulsive behavioural component.
• How do you diagnose Acral lick dermatitis/granuloma?

  Often visually distinctive, especially when small.

  Cytology (squeeze lesion) and deep bacterial culture ideal.

  Biopsies if unsure regarding diagnosis - d/d neoplasia, deep fungal infection.
• Post-grooming folliculitis/furunculosis

  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.
• A 9 year old Rottweiler presents with discharging sinuses on the muzzle. Which investigations will you perform first?

  1 Examine an impression smear of the exudate and deep skin scrapes.

  2 Examine an impression smear of the exudate and submit a sample for fungal culture.

  3 Take biopsies of the lesion and examine deep skin scrapes

  4 Take biopsies of the lesion and submit a sample for fungal culture.

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