Case description
A 55-year-old non-atopic woman with an underlying condition of herniated nucleus pulposus presented slate-grey hyperpigmented macules and patches on face, neck and upper back for 2 years (Fig. 1). She had a history of taking vitamin B12 supplement 600 µg daily due to her neuropathic pain for 3 months before onset of hyperpigmented lesion. She denied having direct contact with cobalt, or any other metals and also agents which can induce slate grey hyperpigmentation including fragrances, rubber products or hair dye. Histopathology of the lesions showed focal vacuolar degeneration of the epidermis with superficial perivascular infiltration of lymphocytes and marked increase of dermal melanophages (Fig. 2).
Fig. 1 . Slate-grey hyperpigmented macules and patches on both cheeks
Fig. 2 . Histopathology from hyperpigmented lesions showed focal vacuolar degeneration of the epidermis and marked increase of dermal melanophages (black arrows) with superficial perivascular lymphocytic infiltration (H&E x40, x100).
Systemic pigmented contact dermatitis was suspected, so patch testing was performed using the European Society of Contact Dermatitis guideline standard and cosmetic series (3). Readings were performed at 48 and 72 hours according to the International Contact Dermatitis Research Group criteria. Pigmented reactions to cobalt showed positive hyperpigmentation after 48 and 72 hours, while other standard and cosmetic allergens were negative (Fig. 3). We further performed tissue biopsy on the positive pigmented reaction. Histopathology showed focal parakeratosis with focal vacuolar interface dermatitis at the dermo-epidermal junction and superficial perivascular infiltration with lymphocytes and melanophages consistent with pigmented systemic contact dermatitis similar to her previous active lesions (Fig. 4). The patient was advised to avoid taking oral vitamin B12. One year after diagnosis, the hyperpigmentation gradually faded after discontinuing cobalamin and adjunctive treatment with topical low potency corticosteroid and topical retinoic acid.
Fig. 3. Patch test read at 72 hours gave hyperpigmented reactions to cobalt (No.22).
Fig. 4 . Histopathology from positive patch test pigmented reaction showed focal vacuolar degeneration of the epidermis with dermal melanophages (black arrows) with superficial perivascular lymphocytic infiltration (H&E x40, x100).