Nail Signs in Systemic Disease
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Direct answer
Clubbing, leukonychia and splinter haemorrhages turn a nail examination into a systems screen: Schamroth's positive window and a Lovibond angle above 180 degrees flag clubbing of cardiac, pulmonary or gastrointestinal origin; Terry's proximal white nails accompany cirrhosis in up to 80% of cases in classical series; the half-and-half (Lindsay) nail belongs to chronic renal failure; and paired Muehrcke bands track serum albumin below roughly 2.2 g/dL. For NEET-PG Medicine, the decisive viva skill is separating true nail-plate signs, which migrate as the nail grows, from nail-bed signs, which stay put.
What you must remember
- Clubbing: loss of the diamond-shaped Schamroth window; Lovibond angle greater than 180 degrees; causes include lung cancer, bronchiectasis, cyanotic congenital heart disease, infective endocarditis, inflammatory bowel disease and cirrhosis.
- Koilonychia (spoon nails): iron deficiency anaemia and Plummer-Vinson syndrome; a degree is physiological in infants.
- Terry's nails: proximal 80% white with a distal pink band — cirrhosis (reported in up to 80%), chronic cardiac failure, diabetes and ageing.
- Lindsay half-and-half nails: proximal white, distal reddish-brown band over about 20–60% of the nail — chronic renal failure, seen in a substantial proportion of dialysis patients.
- Muehrcke's nails: paired, parallel white transverse bands of the nail bed that do not move with growth; classically with serum albumin below about 2.2 g/dL in nephrotic syndrome.
- Beau lines: transverse depressions in the plate itself after high fever, chemotherapy or severe illness — they migrate distally at roughly 3 mm per month for fingernails.
- Mees lines: true plate leukonychia after arsenic or thallium exposure, also migrating with growth.
- Splinter haemorrhages: linear red-brown streaks; proximal or multiple lesions raise endocarditis, though distal single lesions are usually traumatic.
- Pitting with oil-drop discolouration and onycholysis means nail psoriasis; trachyonychia and geometric pitting suggest alopecia areata.
- Yellow nail syndrome triad: slow-growing yellow nails, lymphoedema and pleural effusion.
- Pterygium — scarring wing from proximal nail fold — marks lichen planus.
How to reason through the examination
A 54-year-old alcoholic with distension of the abdomen extends his hands: all ten nails are white in their proximal four-fifths with a narrow distal pink rim, and the index fingers show faint paired transverse pale bands.
Step one: name the signs — Terry's nails first; the paired bands need one decisive test: bands that stay fixed while the plate grows over months are Muehrcke bands of the bed, explained by his ascites and heavy proteinuria through hypoalbuminaemia. Step two: contrast the mimics in one sentence for the examiner — a Beau line or Mees line sits in the plate and marches distally, whereas Muehrcke's lines are bed phenomena that stay still; mixing them is the classic penalty. Step three: complete the systemic sweep that the nails provoke — examine for clubbing and spider naevi, completing the cirrhotic's hand; look for splinter haemorrhages with a new murmur to prompt blood cultures for endocarditis; note half-and-half discolouration and ask about uraemia and dialysis. Step four: localise before systematising — distal onycholysis with oil-drop salmon patches points to psoriasis; proximal whitening with pterygium points to lichen planus and warrants a mucosal examination for the reticular rash. Step five: use growth kinetics prospectively — a Beau line dated from a dengue admission lets you estimate nail growth and reassure the patient that the furrow will grow out.
Where students slip
The commonest slip is presenting every white line as "leukonychia due to calcium deficiency" — true leukonychia reflects keratinisation and trauma, not calcium, and the exam expects the protein-related nail-bed bands instead. The second is failing the fixed-versus-mobile test between Muehrcke and Mees/Beau. Third, quoting Terry's nails for "anaemia" rather than cirrhosis, cardiac failure and diabetes loses the association mark. Fourth, single distal splinter haemorrhage treated as proof of endocarditis — the stem will say "multiple, proximal, with fever and murmur" when it wants the blood cultures. Finally, forgetting yellow nail syndrome's triple presentation when a stem pairs pleural effusion with lymphoedema.
Frequently asked questions
How is clubbing confirmed at the bedside?
Schamroth's window test — opposing the dorsal surfaces of two fingers from the same hand normally leaves a diamond-shaped gap; obliteration of this window, with Lovibond angle exceeding 180 degrees, confirms clubbing.
What is the difference between Muehrcke and Mees lines?
Muehrcke's lines are paired white bands in the nail bed that do not migrate with nail growth and classically accompany hypoalbuminaemia; Mees lines are in the nail plate itself, migrate distally, and follow arsenic or thallium exposure.
Which nail sign is associated with chronic renal failure?
The half-and-half (Lindsay) nail — proximal white discolouration with a distal reddish-brown band — common in uraemia and dialysis.
What causes Beau lines?
Transient arrest of nail matrix activity during severe systemic illness, high fever or chemotherapy, producing transverse plate depressions that grow out at about 3 mm per month.
Which nail features characterise psoriasis?
Pitting, oil-drop salmon discolouration, onycholysis beginning distally, and subungual hyperkeratosis — distinguished from onychomycosis by KOH negativity and asymmetry.