Porphyria Cutanea Tarda

Key Points
Most common subtype of porphyria which typically affects the hands and forearms
Caused by liver enzyme defects
Consists of the formation of erosions, blisters, milia and elevated photosensitivity in the affected area

Porphyria cutanea tarda is the most common form of porphyria, and typically affects the hands and forearms, but may also appear on the neck and face. The condition consists of the formation of erosions (due to minor injury), blisters, milia (tiny cysts which form within healing blisters, and elevated photosensitivity. When the face and/or neck become involved, symptoms may involve brown discoloration around the eyes or increased hair growth in the area. Some cases may be accompanied by induration of the affected skin, alopecia, and ulceration. Urine will be darker than normal in the majority of cases.

Porphyria cutanea tarda is caused by a defect in liver enzymes, and affected persons are often genetically predisposed to develop the condition. It is thought that the condition, which typically presents during midlife, is ushered in by exposure to chemicals which cause an increase in porphyrin production (whose buildup leads to the increase in photosensitivity), including alcohol, oral contraceptives or hormone replacement medications, and excessive iron levels.

Differential Diagnosis (Other conditions with similar appearance)Epidermolysis bullosa
Pseudoporphyria
Epidermolysis bullosa Acquisita
Variegate porphyria
Erythropoietic Porphyria
Hydroa vacciniforme
Lupus erythematosus, Bullous

Diagnosis
Key Points
Diagnosis based on skin biopsy of the affected area
Other tests including complete blood count, urine and fecal examinations, and various laboratory tests may be performed to confirm diagnosis and rule out other conditions

Porphyria cutanea tarda is typically diagnosed based on a skin biopsy of the affected area. Other tests including complete blood count, urine and fecal examinations, and various other laboratory tests may be performed to confirm the diagnosis and to rule out similar appearing conditions.

Treatment
Self care measure include avoiding chemical and sun exposure
Certain tanning solutions may assist in blocking harmful light
Certain therapies are available to assist in relieving symptoms

Porphyria cutanea tarda is best treated by avoiding catalysts of the condition, including exposure to chemicals and sunlight. Use of sunscreens, protective clothing, and even tanning solutions containing dihydroxyacetone can assist in blocking harmful light. Several procedures and therapies exist to reduce the amount of porphyrins in the body, including administration of antimalarial medications, phlebotomy, and autologous red cell blood transfusions.