), resulting in a relatively steady production of phototoxic porphyrins in the liver or bone marrow. These porphyrins accumulate in the skin and, on sunlight exposure (visible light, including near-ultraviolet [UV]), generate cytotoxic radicals that cause recurrent or unremitting cutaneous manifestations.(See also Overview of Porphyrias Overview of Porphyrias Porphyrias are rare disorders in which hemoglobin is abnormally metabolized due to genetic or acquired deficiencies of enzymes of the heme biosynthetic pathway. These deficiencies allow heme... read more .)
Cutaneous porphyrias include
Erythropoietic protoporphyria Erythropoietic Protoporphyria and X-linked Protoporphyria Erythropoietic protoporphyria (EPP) is due to an inherited deficiency in the activity of the enzyme ferrochelatase. X-linked protoporphyria (XLPP) is due to an inherited increase in the activity... read more
(EPP)Congenital erythropoietic porphyria (CEP—see table Some Less Common Porphyrias Some Less Common Porphyrias
)X-linked protoporphyria Erythropoietic Protoporphyria and X-linked Protoporphyria Erythropoietic protoporphyria (EPP) is due to an inherited deficiency in the activity of the enzyme ferrochelatase. X-linked protoporphyria (XLPP) is due to an inherited increase in the activity... read more
(XLPP), sometimes regarded as a clinical variant of EPPHepatoerythropoietic porphyria (HEP—see table Some Less Common Porphyrias Some Less Common Porphyrias
), sometimes regarded as a type of PCT (extremely rare)
The acute porphyrias variegate porphyria (VP) and hereditary coproporphyria (HCP) also have cutaneous manifestations.
In all cutaneous porphyrias except erythropoietic protoporphyria and X-linked protoporphyria, cutaneous photosensitivity manifests as fragile skin and bullous eruptions. Skin changes generally occur on sun-exposed areas (eg, face, neck, dorsal aspects of hands and forearms) or traumatized skin. The cutaneous reaction is insidious, and often patients are unaware of the connection to sun exposure. In contrast, the photosensitivity in erythropoietic protoporphyria and X-linked protoporphyria occurs within minutes or hours after sun exposure, manifesting as a burning pain that persists for hours, without any blistering and often without any objective signs on the skin. However, swelling and erythema may occur. Chronic liver disorders are common in cutaneous porphyrias.
The cutaneous porphyrias are all accompanied by elevated total plasma porphyrins, and are specifically diagnosed by measurements of porphyrins in red blood cells, plasma, urine, and stool, as well as by genetic or enzyme analysis. Treatment involves avoidance of sunlight, measures to protect the skin, and sometimes other treatments directed according to the specific diagnosis.
