Porphyria Cutanea Tarda and Pseudoporphyria
Porphyria cutanea tarda (PCT) is a metabolic disorder caused by genetic or acquired partial deficiencies in the heme biosynthesis pathway. This results in accumulation of photoactive porphyrins, mainly uroporphyrins. Pseudoporphyria is a disorder caused by abnormal drug metabolites that accumulate as photoactive substances. PCT and pseudoporphyria clinically present with symptoms including photosensitivity, skin fragility, bullae, erosions, crusts, and scarring. Cutaneous symptoms exclusively involve sun-exposed skin.
Diagnosis is based on a combination of clinical and immune-histopathological features. The level of uroporphyrin in urine is raised in PCT, whereas it is normal in pseudoporphyria.
Therapy consists of sun protection. Triggering factors like alcoholism, estrogen therapy, and hepatitis C should be eliminated in patients with PCT. Phlebotomy and low-dose chloroquine are therapeutic options. In pseudoporphyria the culprit drug should be stopped.
KeywordsPorphyria cutanea tarda Pseudoporphyria Vesicular bullous disease Sun exposure
We wish to thank M. Gyldenløve (Department of Dermato-Allergology, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark) for providing Figure 22.3.
On the Web
- Rare Diseases Clinical Research Network NHI: https://www.rarediseasesnetwork.org/porphyrias/patients/PCT/