hormonal and metabolic disorders
Erythropoietic Protoporphyria and X Linked Protoporphyria
X linked protoporphyria
 activity of a different enzyme. The increased activity leads to accumulation of the same heme precursor. However, the abnormal gene for this form of erythropoietic protoporphyria is carried on the Inheritance of Single-Gene Disorders , and thus the disorder is called X-linked protoporphyria. Because X-linked protoporphyria is so similar to erythropoietic protoporphyria, it is sometimes regarded as a variant of erythropoietic protoporphyria. 