A bullseye rash (erythema migrans) lesion is considered to be pathognomonic for Lyme disease. What does this difficult word mean? Find out in this glossary entry.
Pathognomonic is defined as a clinical sign or lesion is so characteristic of a specific disease that one can make a diagnosis (definitive or highly suggestive diagnosis) based on simply seeing the sign or lesion.
This word is greek in origin: pathos (disease) and gnome (judgment).1
There are few true single pathognomonic findings that will allow a doctor to definitively diagnose a disease, but sometimes a group of clinical findings and lab test results will be termed as pathognomonic for a particular disease.
Here are some examples of pathognomonic signs seen in veterinary medicine:
- Increased intraocular pressure (IOP) of the eye is often pathognomonic for glacoma.
- Negri Bodies, cellular changes seen on microscopic exam, are considered pathognomonic for Rabies, seen in approximately 70% of Rabies cases.2
- Symmetrical hair loss and enlargement of the vulva in female ferrets is considered to be pathognomonic for ferret adrenal disease.
- Some skin lesions, such as the diamond to rectangular ones seen in swine erysipelas are pathognomonic lesions.
- A "moth-eaten" microscopic appearance of bovine brain tissue is pathognomonic for Mad Cow Disease, or Bovine Spongiform Encephalopathy.
References
Word Origin1 Wikipedia
Rabies - Hydrophobia ref.2 eMedicine
