Pseudoporphyria: A clinical and biochemical study of 20 patients

Objective: To describe the clinical and laboratory findings in patients wit h pseudoporphyria. Patients and Methods: This retrospective review identified 261 patients wit h either porphyrin metabolism abnormalities or pseudoporphyria who were see n at the Mayo Clinic in Rochester, Minn, between 1992 and 1996. All patient s with documented porphyria cutanea tarda (PCT), noncutaneous porphyrias, o r variegate porphyria were excluded. Results: Twenty patients had active cutaneous lesions resembling PCT with n o diagnostic laboratory abnormalities. The major presenting clinical featur es were blistering in 19 patients (95%), scarring in 14 (70%), photosensiti vity in 13 (65%), skin fragility in 13 (65%), and milia in 8 (40%). Histolo gically, of 17 patients tested, 12 (71%) had classic findings of subepiderm al separation with festooning of dermal papillae. None of the 11 patients t ested had hepatitis B or C. In all 20 patients, porphyrin profiles were non diagnostic. Of 16 patients for whom follow-up was available, 11 reported pe rsistent symptoms for a mean of 2.5 years after evaluation. Five patients w ere free of symptoms 1 week to 6 months after discontinuation of the presum ed offending agent. Conclusion: Pseudoporphyria mimics the cutaneous symptoms of PCT in the set ting of normal or near-normal porphyrin levels in the serum, urine, or stoo l. Despite efforts to discontinue an offending medication, symptoms may per sist indefinitely.