Thumb sign – Orris AI

Thumb sign

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The thumb sign refers to two distinct clinical/radiological findings in medicine:

1. Thumb Sign — Epiglottitis (Radiological)

On a lateral neck X-ray, a swollen epiglottis takes on a rounded, bulbous appearance resembling a thumb projecting from the anterior wall of the hypopharynx. This is the classic radiological sign of acute epiglottitis (supraglottitis).

Lateral neck X-ray showing thumb sign of epiglottitis — the bulbous epiglottis is marked by the white arrow

Key points:

An epiglottis width >5.5 mm on lateral neck radiograph constitutes the thumb sign; this has moderate sensitivity but cannot rule out epiglottitis
Usually accompanied by thickening of the aryepiglottic folds and distension of the hypopharynx
Most common pathogen: Haemophilus influenzae (children 3–6 years); also seen in adults
Important caveat: patients with suspected epiglottitis have a tenuous airway — personnel skilled in emergent intubation must accompany the patient to radiology, and equipment for tracheotomy should be ready
CT can also demonstrate supraglottic thickening, but lateral plain film is preferred initially because the recumbent position for CT may provoke abrupt airway occlusion

— Cummings Otolaryngology Head and Neck Surgery; Rosen's Emergency Medicine; Tintinalli's Emergency Medicine

2. Thumb Sign (Steinberg Sign) — Marfan Syndrome (Clinical)

Also called the Steinberg sign, this is a bedside test for arachnodactyly (abnormally long thumb) in suspected Marfan syndrome.

How to perform: The patient adducts the thumb across the palm and closes the fingers over it into a fist. The test is positive if the entire nail (distal phalanx) of the thumb projects beyond the ulnar border of the hand.

Positive Steinberg thumb sign — thumb tip visibly protrudes beyond the ulnar border of the clenched fist, consistent with arachnodactyly in Marfan syndrome

Scoring in the Revised Ghent Nosology (systemic score for Marfan diagnosis):

Finding	Points
Wrist AND thumb sign both positive	3
Wrist OR thumb sign positive	1

Often seen alongside:

Wrist sign (Walker–Murdoch sign): thumb and little finger overlap when gripping the opposite wrist
Pectus deformities, scoliosis, tall stature, superior lens dislocation, aortic root dilation

— Fuster & Hurst's The Heart, 15th Ed.; Emery's Elements of Medical Genetics and Genomics; Miller's Review of Orthopaedics, 9th Ed.

Summary Table

Context	What it means	How detected
Epiglottitis	Swollen, rounded epiglottis resembling a thumb	Lateral neck X-ray
Marfan syndrome	Overly long thumb projecting past ulnar hand border	Clinical bedside maneuver

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