Enrichment of HFE mutations in Swedish patients with familial and sporadic form of porphyria cutanea tarda

Familial and Sporadic Porphyria Cutanea Tarda: Characterization and Diagnostic Strategies

Background: Porphyria cutanea tarda (PCT) occurs in sporadic (sPCT) and familial (fPCT) forms, which are generally clinically indistinguishable and have traditionally been differentiated by erythrocyte uroporphyrinogen decarboxylase (UROD, EC 4.1.1.37) activity. We used UROD gene sequencing as the reference standard in assessing the diagnostic accuracy of UROD activity, evaluating the mutation spectrum of the UROD gene, determining the frequency and disease attributes of PCT and its subtypes in Norway, and developing diagnostic models that use clinical and laboratory characteristics for differentiating fPCT and sPCT.

Methods: All consecutive patients with PCT diagnosed within a 6-year period were used for incidence calculations. UROD activity analysis, UROD gene sequencing, analysis of hemochromatosis mutations, and registration of clinical and laboratory data were carried out for 253 patients.

Results: Fifty-three percent of the patients had disease-relevant mutations, 74% of which were c.578G>C or c.636+1G>C. The UROD activity at the optimal cutoff had a likelihood ratio (LR) of 9.2 for fPCT, whereas a positive family history had an LR of 19. A logistic regression model indicated that low UROD activity, a high uroporphyrin-heptaporphyrin ratio, a young age at diagnosis, male sex, and low alcohol consumption were predictors of fPCT. The incidence of PCT was 1 in 100 000.

Conclusions: Two commonly occurring mutations are responsible for the high frequency of fPCT in Norway. UROD activity has a high diagnostic accuracy for differentiating the 2 PCT types, and a model that takes into account both clinical information and laboratory test results can be used to predict fPCT.

Therapy of porphyria cutanea tarda

Porphyria cutanea tarda (PCT) is the most common type of porphyria. There is an association of PCT with haemochromatosis, diabetes mellitus and hepatitis C infection. The basis of treatment of PCT consists of three elements: avoidance of triggering factors, iron depletion and porphyrin elimination. Alcohol and certain systemic medical drugs, such as oestrogens (or tuberculostatics), should be considered as triggering factors, and as far as possible, avoided. Other triggering factors, such as chronic haemodialysis in renal insufficiency, need a different approach. The hallmark in iron depletion is phlebotomy. Porphyrin elimination is achieved using low-dose chloroquin therapy. The treatment is safe and effective but has its limits in cases with haemochromatosis (HFE) gene mutations. Here iron depletion needs additional phlebotomy. In patients with chronic haemodialysis-associated PCT, chloroquine is ineffective. Erythropoietin, desferroxamine and small-volume phlebotomy have been employed to control the disease. Childhood PCT is very rare. No controlled studies are available, but published experience suggests that body weight-adapted chloroquine therapy or small volume phlebotomy might be useful.

The prevalence of hepatitis C in patients with porphyria cutanea tarda in Stockholm, Sweden

In many countries hepatitis C virus infection has been considered a major factor triggering overt porphyria cutanea tarda. The prevalence of hepatitis C virus infection was retrospectively studied in 87 patients who during a period of 11 years were diagnosed with porphyria cutanea tarda in Stockholm. Among patients with the sporadic form of porphyria cutanea tarda, the prevalence of hepatitis C virus infection was 36.4%. As hepatitis C virus infection may today be successfully treated and as the infection may be clinically silent and thus unknown to the patient, it is important to screen all patients with porphyria cutanea tarda for hepatitis C virus infection.