Most patients have unrelated parents and have inherited a different mutation from each. It is interesting in CEP that residual cosynthase activity persists even in the most severe cases. In CEP excess porphyrins accumulate in bone marrow mostly at the stage of erythroid cell maturation, when hemoglobin synthesis is most active. The symptomology of CEP includes skin blistering which is usually severe, and begins soon after birth. The skin blistering is usually accompanied by anemia and red urine.
Some cases are relatively mild with onset of symptoms in adult life.
Severity depends on the mutations found in each patient and the degree of enzyme deficiency. Skin changes are similar to those of PCT but are usually more severe. Blistering of sun-exposed skin often leads to scarring, infection, and loss of facial features and fingers. Pigmentation changes and hypertrichosis are common. Corneal scarring can be severe.