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

Grade	Finding
I	Increased fluctuation and softening of the nail bed
II	Loss of the normal angle between the nail and the nail fold (Lovibond angle exceeds 180°)
III	Increased curvature of the nail — the classic "parrot beak" or drumstick appearance
IV	Hypertrophic osteoarthropathy — painful swelling of the long bones

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.