The term pathognomonic in radiology, as well as clinical medicine in general, refers to a finding or a sign that is only found in a single specific condition or specific group of conditions, i.e. the finding has 100% specificity. Thus by implication, a pathognomonic finding cannot and does not have a differential diagnosis.
A finding that is pathognomonic today, may not be tomorrow. As new conditions are discovered, old conditions re-classified and case reports published, pathognomicity can change e.g. in the early days of radiology rib notching was thought to be pathognomonic for coarctation of the aorta 1.
It does not imply anything about the sensitivity of the finding, indeed the finding may be rare, and therefore the absence of the finding cannot be taken as a comment on the likelihood of that condition occurring.
The term Aunt Minnie is sometimes also used for imaging signs/findings that are pathognomonic for a condition. However whilst many Aunt Minnies are truly pathognomonic, some are merely classical for a particular condition, but could be rarely found in other disease entities.
History and etymology
Pathognomonic derives from two Ancient Greek roots, παθος (pathos) meaning disease and γνωμων (gnomon) meaning indicator.
- 1. Felson B. Chest roentgenology. AITBS Publishers. (2018) ISBN 978-9374734872. https://www.amazon.co.uk/Chest-Roentgenology-Benjamin-Felson/dp/9374734877