Diagnosis: Porphyria cutanea tarda
The clinical presentation, along with the elevated laboratory values, suggested that this might be a case of porphyria cutanea tarda (PCT). Therefore, a sample of the patient’s urine was examined under Wood lamp and compared to a sample from a healthy control. In the sample of urine from our patient, a vivid red-pink fluorescence could be visualized under the lamp (FIGURE 2), confirming the diagnosis.
The porphyrias are a group of metabolic diseases that affect the heme biosynthesis. They can be classified into 1 of 3 groups, according to clinical features:
- acute hepatic porphyrias, with neurovisceral symptoms (eg, acute intermittent porphyria),
- nonblistering cutaneous porphyrias, with severe photosensitivity but without bullae formation (eg, erythropoietic protoporphyria), or
- blistering cutaneous porphyrias (eg, PCT, hepatoerythropoietic porphyria, and variegate porphyria).
PCT is the most common type of porphyria, with a global prevalence of 1 per 10,000 people.1,2 It affects adults after the third or fourth decade of life.
PCT involves dysfunction of the uroporphyrinogen decarboxylase enzyme (UROD), the fifth enzyme in heme biosynthesis, which catalyzes the conversion of uroporphyrinogen to coproporphyrinogen. This dysfunction causes the accumulation of porphyrinogens that are auto-oxidized to photosensitizing porphyrins.1-4 PCT can be classified as “sporadic” or “familial” based on the absence or presence of UROD mutation. Approximately 80% of cases of PCT are sporadic.2
In sporadic PCT, triggers for UROD dysfunction include alcohol use, use of estrogens, hemochromatosis or iron overload, chronic HCV infection, and HIV infection.1-4 HCV (which this patient had) is the most common infection associated with sporadic PCT, with a prevalence of about 50% among these patients.5
Continue to: Dermatologic manifestations of PCT