Hyperpigmentation in a middle aged woman: a common yet underdiagnosed condition

M elasma is a relatively common, but underdiagnosed, skin condition that can be a challenge to treat for primary care physicians. Our case involves a 39-year-old G3P2A1 Hispanic female not on any hormonal manipulation for birth control and no significant past medical history who presented with a facial rash of 4 years’ duration which had not been relieved by moisturizer and over-the-counter steroid creams. Examination was remarkable for hyperpigmented macules found exclusively on her cheeks (see Figs. 1 and 2). There had been no progression of the rash since the onset, which notably began 1 year after her last labor. She denied associated symptoms of pain, arthralgias, myalgia, fevers, or history of autoimmune disorders, but reported occasional mild pruritus. She was prescribed hydroquinone cream 0.4% to be applied twice daily. Melasma affects approximately 5 million people in the United States (1) with a prevalence rate up to 40% in certain populations (2). It presents as hyper-pigmented macules or patches distributed symmetrically on sunexposed areas such as the upper lip, chin, forehead, or, as in our case, the cheeks. Distribution can be classified into three groups: centrofacial, involving the areas of the forehead, cheeks, nose, upper lip, and chin; malar, which involved only the nose and cheeks; and mandibular, involving solely the ramus of the mandible. Distribution is hypothesized to be related to sebaceous gland density. In rare instances, melasma can occur in extensor aspect of forearms and upper chest. Melasma is much more common in women and has a presumptive genetic component, as 48% have reported a positive family history according to a 2009 survey (3). Pathophysiology of melasma involves excess sunlight/ radiation which causes peroxidation of lipids in the cellular membrane that further generates free radicals subsequently stimulating excess melanin. Melanin is increased in the epidermis and/or dermis. Melanocyte numbers are not increased, but they tend to be larger, more dendritic, and more active. This condition is also seen in pregnancy and is possibly related to hormonal stimulation from