The porphyrias are a group of diseases in which there is a defect somewhere in the complex chain of chemical steps that are required for the synthesis of the molecule known as haem.

Haem is one of a group of compounds called porphyrins and is an iron-containing molecule that combines with the protein globin to form haemoglobin..The disorder results from low levels of the enzyme responsible for the fifth step in heme production. Heme is a vital molecule for all of the body's organs. It is a component of hemoglobin, the molecule that carries oxygen in the blood. PCT is essentially an acquired disease, but some individuals have a genetic (autosomal dominant) deficiency of UROD.

Causes

In the acquired form, the signs and symptoms of this condition are triggered by nongenetic factors such as alcohol abuse, excess iron, certain hormones, and viral infections. However, in the inherited form of the disease, which affects up to 20% of PCT patients, the condition arises from a mutation in the uroporphyrinogen decarboxylase gene, although environmental and chemical factors may trigger or exacerbate symptoms.

Symptoms

People with porphyria cutanea tarda experience chronic, recurring blisters of various sizes on sun-exposed areas such as the arms, face, and especially the backs of the hands. Crusting and scarring follow the blisters and take a long time to heal. The skin, especially on the hands, is also sensitive to minor injury. Hair growth on the face and other sun-exposed area may increase. Liver damage usually occurs; cirrhosis and even liver cancer may eventually develop.

How is it diagnosed?

Sometimes it can be diagnosed by examining the affected person's skin. In other people it's more difficult, requiring blood, urine and stool samples to confirm the diagnosis – they will show elevated levels of porphyrins.

Other important tests may involve checking the iron levels in the blood, looking for previous liver viral infections, and taking a history to detect aggravating drugs.

Treatment

PCT is the most treatable of the porphyrias. Treatment seems to be equally effective in familial and non-familial PCT. Factors that tend to activate the disease should be removed. The most widely recommended treatment is a schedule of repeated phlebotomies (removal of blood), with the aim of reducing iron in the liver. This actually reduces iron stores throughout the body. Usually, removal of only 5 to 6 pints of blood (one pint every one to two weeks) is sufficient, which indicates that iron stores are not excessively increased in most PCT patients. The best guides to response are measurements of serum ferritin and plasma porphyrins

Management

* Avoid alcohol, oestrogen, and iron. * If using pesticides, be very careful to avoid contact with polychlorinated aromatic hydrocarbons (eg. 2,4,5T). * Apply an opaque sun-block and cover up when outside; the responsible light is the "Soret" band at 400 nm which is unfortunately not blocked by most sunscreens.