This 3-year-old boy had a firm, rock-hard papule on his big toe, possibly since birth. The parents deny any known trauma. He is otherwise healthy. Calcium can deposit into the tissues in a variety of settings, leading to calcinosis cutis. This is a case of a subepidermal calcified nodule, a lesion commonly found on the extremities and ears of infants, but also occasionally seen in adults. A subepidermal calcified nodule is an example of dystrophic calcification, likely secondary to trauma.
Histologic sections of acral skin show a large acellular deposit within the superficial dermis and causing an attenuated epidermis and stratum corneum. The deposit shows pinkish amorphous necrotic-appearing debris with a peripheral rim of basophilia.