Cause:SBE, IBD, lung cancer, abscesses, bronchiectasis, benign familial

Si:(Jama 2001;286:341):

• Loss of angle (Lovibond's) between base of nail and dorsal finger surface, hence positive Schamroth sign (no space when dorsal distal phalanges juxtaposed)
• Thickness of distal phalanx at nail bed > thickness at dip joint
• Soft nail bed

Xray:Phalanges and distal arm and leg have periosteal elevations