Dermatology Book

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Digital ClubbingAka: Clubbing, Schamroth's Window Test, Schamroth's Sign, Digital Index

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  1. See Also
    1. Fingernail
    2. Nail Abnormality
    3. Hypertrophic Osteoarthropathy
  2. History
    1. First described by Hippocrates in 5th century B.C.
  3. Definition
    1. Bulbous digital deformity
    2. Watch-crystal deformity of Fingernail
  4. Pathophysiology
    1. Sign of Hypertrophic Osteoarthropathy (Acropachy)
  5. Signs: Schamroth's Window Test for clubbing
    1. Oppose fingers of both hands
    2. Observe space formed between nail bases
      1. Normal: Diamond-Shaped "window" seen
      2. Clubbing:
        1. Window erased
        2. V-shaped gap at distal end of nail is wider
  6. Signs: Digital Index
    1. Use non-elastic string to measure digit circumference
    2. Measure circumference at 2 sites on all 10 digits
      1. Nailbed circumference (NB)
      2. Distal interphalangeal joint circumference (DIP)
    3. Calculate NB/DIP ratio
    4. Results suggestive of digital clubbing
      1. NB/DIP ratio exceeds 1 on all fingers or
      2. Sum of all ten NB/DIP ratios >10
  7. Causes
    1. See Hypertrophic Osteoarthropathy Causes
  8. References
    1. Vazquez-Abad (1989) J Rheumatol 16:1518

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