Clubbing Causes for NEET PG: Grades, Schamroth’s Sign, and the Full List
Reflex · 24 May 2026 · 2 min read
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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.
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FAQ
Frequently asked questions
The questions aspirants ask most about this topic.
The disappearance of the normal diamond-shaped window when two corresponding fingernails are placed back to back — a bedside test for clubbing.
Grade I (increased fluctuation), Grade II (loss of the nail angle), Grade III (parrot-beak curvature), and Grade IV (hypertrophic osteoarthropathy).
Localized causes such as an aortic aneurysm or a Pancoast tumor — distinct from the systemic pulmonary, cardiac, or GI causes that typically produce bilateral clubbing.
In some cases, yes — particularly when the underlying cause (such as an infection or inflammatory condition) is treated early, though long-standing hypertrophic osteoarthropathy is less likely to fully reverse.
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