Clubbing Causes for NEET PG: Grades, Schamroth’s Sign, and the Full List

Clubbing questions in NEET PG General Medicine tend to come in two forms — identify the grade or test, or match clubbing to its underlying cause across systems. Both are fast, high-value marks once the list is organized properly.

The Four Grades of Clubbing

Schamroth’s Window Test

Place the corresponding fingernails of both hands (typically index fingers) back to back. Normally, this creates a small diamond-shaped window between the nail beds. In clubbing, that window disappears, because the increased nail bed angle eliminates the gap. It’s a quick bedside test frequently referenced in clinical vignette questions.

Causes by System

Pulmonary: bronchogenic carcinoma, bronchiectasis, lung abscess, empyema, pulmonary fibrosis, mesothelioma.

Cardiac: cyanotic congenital heart disease, infective endocarditis.

Gastrointestinal: inflammatory bowel disease, cirrhosis, celiac disease.

Others: thyroid acropachy (seen in Graves’ disease).

The Unilateral Clubbing Distractor

Most causes above produce bilateral clubbing. Unilateral clubbing is a specific, high-yield distractor pointing to a localized vascular or mechanical cause — classically an aortic aneurysm compressing local structures, or a Pancoast tumor affecting one side. If a question specifies unilateral clubbing, it’s testing whether you reach for a systemic cause (wrong) or a localized one (right).

Cause-matching questions like this reward organized recall over rote lists — exactly what Reflex’s daily TROCAR Medicine rounds are built to reinforce.