Yellow nail syndrome

Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports

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Yellow nails are the main clinical manifestation (88% of cases) leading to yellow nail syndrome (YNS) diagnosis. Xanthonychia is unsightly and varies from pale yellow to a more or less dark and greenish color. The nail plate becomes thickened with enhanced transverse over-curvature, sometimes with a notable hump cross-ridging and a hard and difficult-to-trim nail plate. The cuticle may disappear, leading to erythema of the proximal nailfold causing a chronic paronychia. The nail grows half as fast and twice as thick. The color of the nail is due to lipofuscin, a pigment arisen from colorless lipid precursors and transformed by oxidation in tissue to produce varying degrees of yellow.

Contrasting with the xanthonychia belonging to YNS, which may improve without specific therapies in about one-half of patients (but may relapse), the other varieties of yellow nails are transient.

Lymphedema is observed in approximately 40% of cases and involves mainly the lower limbs. The most distal body parts are always more severely affected than proximal parts. Stemmer sign, which shows the inability to pinch the skin on the dorsal side or the base of the second toe, is pathognomonic. The face is rarely, and the eyelids are exceptionally, affected.

Respiratory disorders are observed in roughly 50% of patients; the most common respiratory manifestations of YNS are, in descending order, chronic cough, bronchiectasis, recurrent pneumonia, and restrictive lung disease (mainly due to the presence of a pleural effusion).