While ""regular"" otitis externa has existed since time immemorial, the first credited description of the necrotizing variety goes to French physician Adolphe Toulmouche in 1838. Toulmouche studied directly under René Laennec, the inventor of the stethoscope.

#pathognomonic #meded

From the pages of Pathognomonic Signs of Disease: bucket-handle fracture. A crescent-shaped metaphyseal fragment lifted from a long-bone end, usually near the growth plate. This is classic for non-accidental trauma in a young child.

#pathognomonic #meded

Are hepatic daughter cysts pathognomonic for echinococcosis? Yes! Truly! Complex cysts, septations, and debris have broad differentials, but true daughter cysts are endogenous brood capsules of a hydatid cyst and have not been documented in any other hepatic disease.

#pathognomonic #meded

Are Reinke crystals pathognomonic for Leydig cell tumor? Not really. They DO indicate a Leydig cell, but being a Leydig cell alone is not a crime...or a disease. So calling it "pathognomonic" is not correct, nor does it mean the cells are malignant.

#pathognomonic #meded

Christmas tree rash mechanism? Since the cause of pityriasis rosea is uncertain, this mechanism is also uncertain. The trunk lesions seem to align Langer's lines.

#pathognomonic #meded

From the pages of Pathognomonic Signs of Disease: American dermatologist Frank Crowe published his findings in 1964 where approximately 20% of NF1 cases he saw had axillary freckling. It was dubbed "Crowe's sign" in his honor.

#pathognomonic #meded

From the pages of Pathognomonic Signs of Disease: Giant cytoplasmic granules in leukocytes. These are oversized azurophilic inclusions on Wright-Giemsa smear, especially in neutrophils. This is a historically pathognomonic finding for Chédiak-Higashi syndrome.

#pathognomonic #meded

Are Call–Exner bodies pathognomonic for granulosa cell tumor? Not strictly. “Call–Exner-like” spaces may contain mucin or other eosinophilic material instead of basal lamina material as in true Call-Exner bodies.

#pathognomonic #meded

An Inflamed DIP joint means swelling plus redness at the distal interphalangeal joint (not just bony enlargement). It's an important clue to psoriatic arthritis, but also happens in gout, pseudogout, and erosive osteoarthritis.

This and others at pathognomonic.com

#pathognomonic #meded

Choroid tubercle mechanism: Hematogenous tuberculosis seeds the choroidal vasculature, where granulomatous inflammation produces pale yellow choroidal lesions. The choroid is so susceptible in part because it has the highest blood flow per unit tissue in the body.

#pathognomonic #meded

Dutch ophthalmologist Jan van der Hoeve coined the term "phakoma" in 1923 after the Greek phakos for ""lentil,"" as he observed multiple "mother spots" and round birthmarks on patients with tuberous sclerosis. Retinal phakoma are considered pathognomonic for the disease.

#pathognomonic #meded

Lisch Nodules: Small, dome-shaped, well-defined tan to brown raised spots on the surface of the iris, typically multiple, smooth, and visible on slit-lamp eye exam rather than to the naked eye. The academy tells us this automatically points to neurofibromatosis type 1.

#pathognomonic #meded

Is erythema migrans pathognomonic for Lyme disease?

Well, no.

STARI can produce an indistinguishable expanding rash, and similar lesions occur with Asian tick-associated rash illness; tick saliva may sometimes cause the eruption without Borrelia.

#pathognomonic #meded

PAS-positive macrophages point to Whipple’s disease. Key mimic: MAC, which is PAS-positive but acid-fast positive; T. whipplei is acid-fast negative. Rhodococcus and fungi can also complicate specificity. That's why this is not truly pathognomonic.

#pathognomonic #meded

Burton’s line mechanism: Lead in gingival capillaries reacts with hydrogen sulfide made by oral anaerobic bacteria, depositing dark lead sulfide at the gumline. It's an elegant intersection chemistry, toxicology, and microbiology.

#pathognomonic #meded

The moment anterior lenticonus enters the pathognomonic arena: A paper published in 1966 by Arnott, Crawfurd, and Toghill details a case report and in-depth literature review linking anterior lenticonus as a specific sign of Alport’s syndrome.

#pathognomonic #meded

Pneumatosis intestinalis: linear or bubbly gas within the bowel wall on abdominal imaging. When this pattern appears in preterm neonates, necrotizing enterocolitis should move high on the differential.

#pathognomonic #meded

Is electrical alternans pathognomonic for a large pericardial effusion? Not even close. It also occurs with rapid supraventricular rhythms, myocardial ischemia, intermittent bundle or fascicular block, hypertrophic cardiomyopathy, severe hypocalcemia, and drug toxicity.

#pathognomonic #meded

Howell–Jolly bodies are nuclear remnants inside RBCs, seen during hyposplenia. A worthwhile association to know, but far from pathognomonic. They also show up in certain chemotherapies and corticosteroids, megaloblastic anemia, myelodysplastic syndrome, and hemolytic anemia.

#pathognomonic #meded

Bilateral conjunctival suffusion, the hallmark of leptospirosis...on exams. Its mechanism: Leptospira injures conjunctival endothelium and loosens junctions, causing vascular leak and red eyes without purulent conjunctivitis.

#pathognomonic #meded