Test your diagnostic skills in our regular dermatology quiz. What is the cause of this asymptomatic eruption?
A 52-year-old woman presents with a reticulate, erythematous and pigmented eruption on her lower back (Figure). It is asymptomatic and was first noticed by her husband four months ago. The patient is generally well but suffers from osteoarthritis that affects her lower back. She regularly takes diclofenac and paracetamol for pain relief.