The mother of a 10-year-old boy brings him in for evaluation of his moles (which are all benign). During the visit, the mother asks about the lesions on the first 2 knuckles of his right hand; she initially noticed them several months earlier. The boy is otherwise healthy.
Further questioning revealed that the patient had a “nervous,” or compulsive, habit of chewing and biting on his knuckles, especially during stressful situations at school.
Warts would have a more verrucous appearance, and psoriasis would be more erythematous and scaly. Lichen planus is characterized by polygonal purplish papules, which are unlike the changes seen here. Dermatomyositis can produce erythematous papules overlying the joints of the hands; however, these lesions are associated with proximal muscle weakness, which was absent in this healthy 10-year-old boy.