Derm Dx: Rash on the Abdomen and Upper Arms

A 75-year-old, obese woman is referred for evaluation of a rash affecting her abdomen and upper arms. The condition was first noted 6 months prior to evaluation and is asymptomatic. Medical history includes adult-onset diabetes and hypertension. Prior treatments for the rash include ketoconazole shampoo and triamcinolone cream, both of which were ineffective.

Can you diagnose this condition?