Porphyrias and porphyrins

Porphyria cutanea tarda

Porphyria cutanea tarda (PCT) is a metabolic disorder of haem biosynthesis caused by decreased activity of uroporphyrinogen decarboxylase. Porphyria cutanea tarda is manifest by fragility, erosions, bullae, milia and scars on sun-exposed skin. Excess porphyrins in the skin interact with light of approximately 400 nm-wavelength radiant energy, forming reactive oxygen species. Porphyria cutanea tarda is categorized as familial, acquired or toxic. Factors that may induce clinical expression of PCT in susceptible individuals include alcohol, oestrogen, iron, polyhalogenated compounds and viral infections. Porphyria cutanea tarda is associated with an increased incidence of the haemochromatosis gene. Treatments for PCT include withdrawal of aggravating factors, phlebotomy and oral antimalarial medications.

Cutaneous deposition diseases. Part I

The cutaneous deposition disorders are a group of unrelated conditions characterized by the presence of either endogenous or exogenous substances within the dermis or the subcutis. Part I of this two-part series will focus on metabolic processes involved in the endogenous deposition in the various forms of amyloidosis, porphyria, colloid milium, and lipoid proteinosis. We will also review the clinical, histologic, biochemical, and ultrastructural findings relevant to each disorder. Basic mechanisms of pathogenesis, diagnostic modalities, and treatment options are also discussed.

Cimetidine in the treatment of acute intermittent porphyria

Treatment options for AIP remain limited. Although no single therapy has been proven superior in clinical trials, intravenous hemin appears to be more effective than increased carbohydrate intake, and remains the treatment of choice. At usual dosages the average wholesale price of hemin is $120-475 per day (for a patient weighing 70 kg), compared with $2.50 per day for cimetidine. Cimetidine may offer a more cost-effective and easily administered alternative to hemin therapy. The optimal dosage and duration of treatment with cimetidine have not been established and are likely to be patient-specific. Oral doses of 800 mg/d have been used. In addition to its potential for treatment, cimetidine may also have a role in prophylaxis of acute episodes by maintaining a baseline suppression of ALA synthase activity. Until well-designed, controlled clinical trials demonstrate its efficacy and compare it with other treatment options, cimetidine should be reserved for use only after standard treatment modalities have failed.

Neurologic disease in a child with hepatoerythropoietic porphyria

Hepatoerythropoietic porphyria (HEP) is a rare, autosomal recessive disorder due to deficient uroporphyrinogen decarboxylase enzyme activity. Patients exhibit photosensitivity, red urine, hypertrichosis, and characteristic serum and urine porphyrin profiles. Two siblings had the classic clinical and biochemical findings of HEP. The older patient developed a left-sided hemiparesis accompanied by an abnormal brain magnetic resonance imaging study. Although central nervous system abnormalities are a common feature of other hepatic porphyrias, they have not been previously documented in association with HEP.