Dermatology

• describe the lesion

  circular alopecia

  
• what s your top differential?

  ringowrm

  
• Papules = raised and firm lumps less than 1cm
• nodule raised and firm lumps larger than 1cm
• what is your top differential?

  pemphigus foliaceous

  
• in general crusts are non-specific but they are more helpful on the pinna, scale and alopecia on the trunk are also not helpful. Punched out ulcers on the pads are very helpful as this only occurs in auto-immune conditions. Hence, some lesions are more useful than others.
• lesion morphology

  • Primary e.g. papules, pustules, follicular casts
  • Look for these, they are important diagnostically as differentials are often limited
  • Often transient
  • Secondary e.g. crusts
  • These result from the primary lesion or an external factor
  • Maybe useful diagnostically
  • NB Above may co-exist and/or change as disease progresses
• common causes of skin disease in dogs

  • Ectoparasites
  • Infections
  • Staphylococci
  • Malassezia
  • Dermatophytes
  • Viral/protozoal
  • Allergic
  • Neoplastic
  • Endocrine
• common causes of skin disease in cats

  • Ectoparasites
  • Infections
  • Dermatophytes
  • Viral
  • Staphylococci
  • Malassezia
  • Allergic
  • Neoplastic
• It is important to remember where different parasites live as this can help indicate what test to do.

  • Cheyletiella remains on the skin surface so can be diagnosed with a superficial skin scrape
  • Sarcoptes buries in the epidermis so needs a deem skin scrape.
  • Demodex (There is more than one) is even deeper so these skin scrapes need to be done until they bleed.
  • There are different types of demodex e.g., demodex gatoi which lives on the surface, which can present slightly differently.
• what is your diagnosis?

  sarcoptes

  
• what is your diagnosis?

  Cheyletiella

  
• D gatoi is a surface mite while D canis is deep
• chewing / biting lice has a head wider than the horax
• sucking lice has a head narrower than the thorax
• lice are insects so have 6 legs while mites are arachnids so have 8
• surface mites have longer legs than burrowing mites
• Which sample will you take to investigate the presence of bacteria on the surface of an exudative plaque?

  Direct impression smear