1. Clubbing
2. Koilonychia
3. Onycholysis, pitting, thickening
4. Colors: leuconychia, yellow, blue, red, Terry's, melanonychia
5. Nail bed: pallor, telangiectasia
6. Splinter hemorrhages
7. Bands: Beau's, Mees', Muehrke's

Clubbing

• What: when view fingernail from side, angle of base of nail is >160°.
• DDx: CLUBBING:
  • Cyanotic heart dz
  • Lung dz: hypoxia, lung CA, bronchiectasis, CF
  • UC, Crohn's
  • Biliary cirrhosis
  • Birth defect [harmless]
  • IE
  • Neoplasm [esp. Hodgkins]
  • GI malabsorption
• Staging:
  1: Loss of normal 160° angle at base of nail. Schamroth's window test: pt's holds 2 index finger nails touching each together: if normal, will show a diamond-shaped window.
  2: AP curvature increased.
  3: Bouncy, spongy nail when examiner presses down on nail.
  4: Drumstick shaped fingertip.
  5: Pt has wrist pain and wrist onion skinning.
  6: Hypertrophic osteopathy.

Koilonychia

• What: misshapen, spoon-shaped nails.
• DDx:
  • Iron deficiency
  • Birth abnormality, rarely

Onycholysis

• What: distal nail separation.
• DDx:
  • Trauma
  • Psoriasis
  • Thyrotoxicosis

Pitting

• DDx:
  • Psoriasis
  • Atopic eczema
  • Allopeica areata

Thickening

• What: extremely thickened nail, esp. great toe
• DDx:
  • Geriatric pt: onychogryphosis
  • Psoriasis
  • Local fungal infection 

Nail color: leuconychia

• What: leuco- means white, like a leucocyte.
• DDx:
  • Hypoalbuminemia

Nail color: yellow

• DDx:
  • Nicotine stains
  • Yellow nail syndrome [peripheral edema, bronchiectasis, pleural effusion] 

Nail color: blue

• DDx:
  • Cyanosis
  • Ochonosis
  • Wilson's [esp. lulunae of nails]
  • Blue-red: polycythemia

Nail colour: red

• DDx:
  • Cherry red: CO poisoning

Nail colour: Terry's nails

• What: distal half is brown-red, while proximal half is white-pink.
• DDx:
  • Cirrhosis
  • Chronic renal failure

Nail color: melanonychia

• What: multiple, brownish, longitudinal streaks
• DDx:
  • Black pt: normal
  • White pt: melanoma under fingernails 

Nail bed pallor

• What: pallor of the flesh underneath the nails.
• DDx:
  • Anemia. See Anemias Reference.

Nail bed erythema/ telangiectasia

• What: flushed skin or distended blood capillaries below and around nail, esp at nail base. See Skin Lesion Terminology Reference.
• DDx:
  • SLE

Splinter hemorrhages

• What: small, linear hemorrhages under the nail.
• DDx: SPLINT:
  • Sepsis elsewhere
  • PAN/SLE/RA
  • Limey [vitamin C deficiency]
  • IE
  • Neoplasm [hematologic]
  • Trauma

Bands: Beau's lines

• What: multiple, unpigmented, transverse lines, from an illness severe enough to transiently stop nail growth.
• DDx:
  • Shock Hx
  • Malnutrition Hx
  • Weight loss Hx

Bands: Mees's lines

• What: solitary, white, transverse band
• DDx:
  • Renal failure
  • Chemotherapy
  • Arsenic ingestion

Bands: Muehrke's

• What: multiple, opaque, transverse bands
• DDx:
  • Hypoalbuminemia
  • Chemotherapy