Vitamin B12 induced acneiform eruption.

A 47-year-old, north african, male patient, has recently been diagnosed with pernicious anemia, treated with weekly intramuscular hydroxocobalamin. 6 weeks after its initiation, the patient presented a sudden, extensive and monomorphic eruption of inflammatory papulo-pustules and nodules, affecting the face, and the trunk. The eruption was pruritic, and comedones were also present, on the chest. The patient was diagnosed with vitamin B12-induced acneiform eruption. Levels of vitamin B12 were normalized. Hydroxocobalamin was therefore stopped and lymecycline was started, allowing a complete resolution of the lesions within 3 months. Drug intake, sudden and uncommon age of onset, pruritus, a monomorphic pattern and an involvement of extra-seborrheic areas are features that distinguish acneiform eruptions from acne vulgaris.