A 56-year-old man comes to the physician because of an intermittent, non-pruritic skin rash that appeared approximately one year ago. The rash starts as skin irritation followed by blistering and then crusting that is sometimes very painful. The rash affects the back of his hands and sometimes his neck. He initially thought the irritation was caused by his soap, but switching to a different brand did not help. He feels he is in good health otherwise and does not see doctors. He was told that he has "borderline diabetes" and high blood pressure several years ago. He is a former intravenous drug abuser. He smokes one pack of cigarettes per day and drinks beer over the weekend.
His blood pressure is 152/77 mm Hg and pulse is 82/min. His BMI is 32 kg/m². The oral mucosa is moist without any lesions. There is no lymph node enlargement. Lungs are clear to auscultation and there are no heart murmurs. Abdomen is non-tender. Inspection of the skin reveals areas of erosion, crusting, skin hyperpigmentation, and fine scarring affecting the dorsum of both hands, ears, extensor surfaces of the arms, and the back of the neck.
Which of the following is most likely related to this patient's condition?

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11ec193a_9777_c92a_853d_3d6bf43c7e8f_MD0002_00 This patient's presentation is consistent with porphyria cutanea tarda (PCT). Porphyrias are hereditary or sporadic disorders of heme synthesis. Porphyria cutanea tarda is the most common porphyria and presents with skin blisters and/or skin hypo/hyperpigmentation in sun-exposed areas. There is a strong association between the sporadic form of PCT and hepatitis C (HCV), with significant geographic variability. Over 50% of patients in the United States with newly diagnosed PCT also have HCV, but the exact underlying pathophysiology is unknown. Diagnosis is suggested clinically by skin findings and confirmed by elevated serum/urine uroporphyrin levels. Patients diagnosed with concomitant HCV require treatment for HCV in addition to phlebotomy. If phlebotomy is not possible, alternative therapies include iron chelation therapy or hydroxychloroquine. Patients should also avoid sun exposure by wearing protective clothing. (Choice B) Fat malabsorption (steatorrhea) can be due to bile acid deficiency, pancreatic enzyme insufficiency, poor absorption secondary to defective mucosa (e.g., abnormal bacterial overgrowth), or short bowel syndrome. This patient's lack of steatorrhea makes this unlikely. (Choice C) Insulin resistance is classically associated with acanthosis nigricans. acanthosis nigricans (Choice D) Lung malignancies can be associated with paraneoplastic syndromes (e.g., dermatomyositis), but not usually with PCT. (Choice E) Parasitic infections are usually not associated with PCT. Educational objective: Porphyria cutanea tarda usually presents with skin lesions (e.g., blisters, bullae, scarring) in sun exposed areas and is associated with hepatitis C infection. Diagnosis is confirmed by elevated serum/urine uroporphyrin level. Treatment involves phlebotomy and treatment for HCV in patients diagnosed with the virus. __________ References: Prevalence of hepatitis C infection in porphyria cutanea tarda: systematic review and meta-analysis (http://www.ncbi.nlm.nih.gov/pubmed/12971974)

A 56-Year-Old Man Comes to the Physician Because of an Intermittent