Osteoma cutis may occur in numerous skin disorders including long-standing acne. An unusual type of postacne osteoma cutis presents with small pigmented nodules in the area of involvement. X-ray diffraction analysis was carried out on an osteoma surgically removed from a patient with moderately severe long-standing acne. The analysis results confirmed that the crystalline component of the specimen is hydroxyapatite, a primary constituent of true bone.
Basler RSW, Taylor WB, Peacor DR. Postacne Osteoma CutisX-ray Diffraction Analysis. Arch Dermatol. 1974;110(1):113-114. doi:10.1001/archderm.1974.01630070077022