Knuckle lesions in inherited and acquired disorders

Skin lesions occurring over the knuckles can be a primary or characteristic manifestation of a disorder. Characteristic knuckle lesions may also be important cutaneous features of various internal disorders when they serve as useful clinical pointers, as well as may speak of the disease severity in certain instances. Furthermore, knuckle lesions also speak of various external factors as the underlying cause of the disease/lesions, such as trauma – occupational or otherwise, and contact dermatitis. Although knuckles essentially imply dorsal aspect of the metacarpophalangeal joints, many of the lesions described as those 'involving the knuckles' are seen over the proximal and/or less frequently, the distal interphalangel joints as well. This review presents a compilation of various inherited and acquired dermatoses and dermatological manifestations of various internal disorders associated with different forms of knuckle lesions.