Pathognomonic

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 .

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.

Examples of pathognomonic imaging signs

• bamboo spine: ankylosing spondylitis
• exclamation mark sign: limy bile
• Tam o' Shanter sign: Paget disease
• Wimberger sign: congenital syphilis

History and etymology

Pathognomonic derives from two Ancient Greek roots, παθος (pathos) meaning disease and γνωμων (gnomon) meaning indicator.