The differential diagnosis of bluish-gray pigmentation of the skin includes dermal melanocytosis, malignant melanoma and metallic discoloration. Of these disorders, metallic discoloration, which develops from deposits of fine metallic particles on the skin, is an uncommon dermatologic disease. We report a case of metallic discoloration of the right shin caused by titanium alloy prostheses in a patient with right total knee replacement. The patient had bluish-gray pigmentation on her right shin as well as pain while walking. Histopathologic findings of the skin lesion showed abundant black particles in the perivascular area of the lower dermis. Polarizing microscopy revealed refractile foreign materials in the dermis. An energy dispersive X-ray spectrophotometer unit attached to a transmission electron microscope detected titanium and aluminium peaks in the specimen.
Keywords: Metallic discoloration; Titanium-aluminium alloy; Total knee replacement.