Sienna is a 16-year-old who presents with gradually progressive discolouration on the chest and neck (pictured) over the past 12 months.

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<p>Sienna is a 16-year-old who presents with gradually progressive discoloration on the chest and neck (pictured) over the past 12 months.</p><p>The rash is otherwise asymptomatic and no other areas are affected.</p><p>Sienna is generally well, with no past history of note, no known allergies and taking no medications.</p><p>Her BMI is in the overweight range and there is no family history of dysglycaemia.</p><p>She has tried antifungal shampoos and creams, with no effect.</p><p>On examination, the only findings of note are reticular hyperpigmented papules and plaques on the anterior chest, posterior neck (pictured) and bilateral axillae.</p><p>These do not fluoresce under Wood’s lamp. Fungal cultures are negative, and fasting BSL and insulin are normal.</p>

Dr Kate Kelso is a GP and medical editor at Australian Doctor.