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Porphyria cutanea tarda (PCT) in patients with CKD commonly presents as bullae on the dorsal surfaces of the hands and feet (Figure 7); bullae sometimes occur on the face as well, usually accompanied by facial hyperpigmentation (sclerodermoid plaques) and hypertrichosis.[113] Secondary infection of the bullous lesions often occurs and healing of these lesions is associated with scarring. The sporadic form of PCT occurs in approximately 5% of patients on dialysis; this form is caused by increased uroporphyrin concentrations and can be triggered by ingestion of alcohol, estrogens or iron and by chronic infections such as hepatitis B, hepatitis C or HIV.[113] Typical linear staining of IgG, C3 and fibrin at the dermoepidermal junction is noted on skin biopsy in patients with PCT; blood vessels are surrounded by periodic acid-Schiff-positive material with little inflammation.[113] Pseudoporphyria is triggered by medications (e.g. amiodarone, tetracyclines and naproxen); this condition presents in the same way as PCT but differs from PCT in that the patient's uroporphyrin levels are normal.[113]
Sun protection is a crucial element of treatment for patients with PCT. Uroporphyrin levels can be lowered by improving dialysis efficacy through use of high-flux membranes.[114] Drastic measures to lower uroporphyrin concentrations further (e.g. phlebotomy) are not routinely advocated. Iron or estrogen supplementation should be interrupted during treatment for PCT, vitamin B1 deficiency should be excluded, and patients should abstain from alcohol.[114]