That temperamental dignotions, and conjecture of prevalent humours, may be collected from spots in our nails, we are not averse to concede.
—Sir Thomas Browne
IT HAS long been appreciated that systemic disease can produce changes in the nails. Hippocrates, in his classic description of the clubbing phenomenon in empyema, first directed attention to the systemic onychopathies. A relative spate of descriptive reports in more recent times was begun by J. C. Reil's 1792 notation on white transverse bands and sulci following febrile diseases.1 Gradually, such entities as Beau's lines,2 Mees' lines,3 splinter hemorrhages,4 koilonychia,5 pigmented nails,6 onycholysis,7 Terry nails,8 Muehrcke's striae,9 azure lunulae,10 rubra lunulae,11 platonychia,12 the nail-patella syndrome,13 and the yellownail syndrome,14 came to be recognized as nail signs of diagnostic significance. There are now more than 40 described onychopathies due to systemic illnesses and three monographs focusing on the nails in disease.1517
That certain nail
Lindsay PG. The Half-and-Half Nail. Arch Intern Med. 1967;119(6):583-587. doi:10.1001/archinte.1967.00290240105007