Porphyria cutanea tarda presents with blistering and crusted skin lesions on the back of hands and other sun-exposed areas of the body. Other common features include skin fragility, with minor trauma causing blister formation, hypertrichosis, skin hyperpigmentation, and dark or reddish urine.
Factors that contribute to susceptibility include alcohol use, smoking, hepatitis C, HIV, iron overload, hereditary haemochromatosis gene mutations, oestrogen treatment, and uroporphyrinogen decarboxylase (UROD) mutations.
Results from an acquired, substantial deficiency of UROD in the liver.
Diagnosis is established by finding substantial increases in porphyrins in urine or plasma and excluding other blistering cutaneous porphyrias.
Treatment includes repeated phlebotomy or low-dose hydroxychloroquine or chloroquine; remission can usually be achieved within 6 months.
Porphyria cutanea tarda (PCT) is a blistering cutaneous condition caused by a substantial deficiency of hepatic uroporphyrinogen decarboxylase, the fifth enzyme in the haem biosynthetic pathway. Substrates for the deficient enzyme, which are porphyrinogens (reduced porphyrins), accumulate in the liver, are oxidised to porphyrins, transported to the skin, and cause photosensitivity. PCT is rare (prevalence approximately 1 in 25,000); however, it is the most common of the porphyrias. It is usually associated with liver cell damage.
History and exam
Key diagnostic factors
- presence of risk factors
- blistering skin lesions
Other diagnostic factors
- skin hyperpigmentation
- scarring alopecia
- red urine
- male, middle-aged, white people
- alcohol use
- oestrogen therapy
- hepatitis C
- hereditary haemochromatosis gene (HFE) mutation
- uroporphyrinogen decarboxylase (UROD) mutations
- exposure to halogenated polycyclic aromatic hydrocarbons
- reduced levels of antioxidants
- end-stage renal disease
- diabetes mellitus
1st investigations to order
- plasma total porphyrins
- plasma fluorescence emission
- urinary total porphyrins
- erythrocyte total porphyrins
Investigations to consider
- fractionation of plasma porphyrins by high-performance liquid chromatography (HPLC)
- fractionation of urinary porphyrins by HPLC
- erythrocyte uroporphyrinogen decarboxylase (UROD) activity
- faecal porphyrins
- DNA studies
- Liver function tests
- serum ferritin
- liver biopsy
- skin biopsy
- serum HIV enzyme-linked immunosorbent assay
- serum hepatitis C surface antibodies
no phlebotomy contraindications
phlebotomy contraindicated or poorly tolerated
relapse after remission
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