A solitary lesion of idiopathic calcinosis cutis in an infant: subepidermal nodular calcinosis or milia-like idiopathic calcinosis cutis?

Milia-like idiopathic calcinosis cutis (MICC) and subepidermal calcified nodule (SCN) are described as different entities under the heading of idiopathic calcinosis cutis. Although there are some clinical differences, they share many features. Whereas MICC lesions are located mostly on the extremities and rarely on the face, SCN manifests itself mostly on the face, rarely on the extremities. Milia-like idiopathic calcinosis cutis almost always presents with multiple lesions, whereas SCN shows mainly solitary and rarely multiple lesions. Association with Down syndrome (DS) has been reported in up to two-third of the cases with MICC, but not in SCN. We herein present a 5-months-old girl without DS, manifesting a 2mm solitary, white hard papule surrounded by erythema, located on the finger. Histopathologic findings revealed the presence of dermal calcium deposits. When a solitary papular lesion of idiopathic calcinosis is seen in a child, especially if not associated with DS, it is difficult to differentiate MICC from SCN. We believe that these entities may represent variants of the same pathology and it may be more appropriate to designate a solitary lesion as SCN, regardless of its location.