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).