From the Guidelines
Porphyria cutanea tarda (PCT) is diagnosed through a combination of laboratory tests, including measuring urinary porphyrins, particularly uroporphyrin and heptacarboxyl porphyrin, and plasma porphyrin levels, which show a characteristic fluorescence peak, as recommended by the most recent study 1. The primary diagnostic tests for PCT include:
- Measuring urinary porphyrins, which are typically elevated in PCT patients
- Plasma porphyrin levels, which show a characteristic fluorescence peak
- Fractional analysis of porphyrins in urine, faeces, and erythrocytes to differentiate between bullous porphyrias, as stated in the study 1 Other important tests include:
- Liver function tests
- Hepatitis serology
- Iron studies, including ferritin levels
- Genetic testing for HFE mutations to identify underlying factors, as mentioned in the study 1 The most effective treatment approach for PCT is a combination of phlebotomy, low-dose antimalarial medications, and addressing underlying factors, as supported by the study 1. Treatment of PCT focuses on three main approaches:
- Phlebotomy (removal of 450-500 mL of blood every 2 weeks) to reduce iron stores until ferritin levels reach 20-50 ng/mL
- Low-dose antimalarial medications, such as hydroxychloroquine (100 mg twice weekly) or chloroquine (125 mg twice weekly), to mobilize porphyrins from the liver
- Addressing underlying factors, including stopping alcohol consumption, discontinuing estrogens, treating hepatitis C if present, and avoiding sun exposure by using protective clothing and high-SPF sunscreen, as recommended in the study 1 Most patients respond well to treatment within 6-12 months, though they may require maintenance therapy and should have porphyrin levels monitored periodically to detect recurrence, as stated in the study 1.
From the Research
Diagnostic Tests for Porphyria Cutanea Tarda
- The diagnosis of porphyria cutanea tarda (PCT) can be made based on the skin symptoms, a characteristic urinary porphyrin excretion profile, and the detection of isocoproporphyrin in the feces 2.
- Gross examination of the urine can provide a valuable clue, since urine of PCT patients is red to brown in natural light and pink to red in fluorescent light 3.
- Biopsy of a bullous lesion is useful to rule out other diseases 3.
- Confirmation of PCT requires measurement of porphyrin levels in a 24-hour urine collection 3.
- In red blood cells of individuals with type II PCT, uroporphyrinogen decarboxylase (UROD) activity is decreased by approximately 50% due to heterozygous mutations in the UROD gene 2.
Treatment Options for Porphyria Cutanea Tarda
- Therapeutic measures for PCT include avoidance of exacerbating factors, especially ultraviolet light, ethanol, and certain medications 3.
- Phlebotomy or chloroquine therapy is reserved for patients in whom conservative measures fail 3.
- Phlebotomy is consistently effective and probably exerts its effect mainly by reduction of iron stores 4.
- The effect of phlebotomy on patients with PCT is a decrease in urinary uroporphyrin excretion, which can lead to remission of the disease 4.
- Other therapeutic strategies that can be applied include reducing the availability of iron in the liver and genetically steered inducibilities of the genes programming for CYP4501A and the rate-limiting enzyme in heme synthesis, 5-aminolevulinate synthase 5.