Late-onset Form of EPP May Be Cause of Skin Reactions to Sun in Adults

Inherited, genetic late-onset erythropoietic protoporphyria (EPP), a rare form of EPP that usually manifests later in life, should be included when considering a diagnosis of adults with generally mild skin itching and rashes in sun-exposed areas, a review study proposed.

The study, “Inherited genetic late‐onset erythropoietic protoporphyria: A systematic review of the literature,” was published in the journal Photodermatology, Photoimmunology & Photomedicine.

EPP, the most common type of porphyria in children, is characterized by the presence of acute skin problems in sun-exposed areas, including pain, burning, stinging, and itching, which are often associated with redness and swelling.

While most prevalent and best-known as a disease found in children, two other types of EPP exist. One is an acquired form that can appear at any age and is associated with blood disorders. The other is less well-studied and more rare, and inherited like the most common childhood form but begins to affect people as adults.

This disease tends to be milder when first symptoms come in adulthood than the form that affect children, the study noted.

To gain a better and deeper understanding of this inherited late-onset form of EPP, researchers at Rabin Medical Center and Tel Aviv University, in Israel, conducted a systematic review of published literature on the disorder.

They identified 1,514 potentially relevant studies describing patients with this form of EPP. After excluding studies that did not meet their inclusion criteria, such as having too broad an EPP focus, they arrived at six to be included in the final analyses. Of note, only patients whose first signs of disease came at or after age 18, and who showed no evidence of any blood disease, were considered to have this rare form of EPP.

In total, seven patients (four men and three women) from six families were in the analyses. They were at a mean age of 34.2 when first experiencing disease symptoms, and a mean age of 41.8 when diagnosed.

Solar exposure was identified as the trigger for  EPP onset in two patients. Apart from sun exposure, no other disease triggers were identified.

Common symptoms in three patients each included photosensitive skin rashes, and painful eruptions of patches and plaques, and itching in one patient.

Liver function tests were normal in four patients, and unavailable in two. None of the patients showed signs of liver damage or required a liver or bone marrow transplant.

In the four patients who underwent genetic testing, three had a mutation in the FECH gene, which provides instructions for making the ferrochelatase enzyme. This enzyme is needed for the production of heme, a key molecule for red blood cells to transport oxygen.

Treatment consisted mainly of sun avoidance. One patient was taking beta carotene, a potent antioxidant, daily, and another responded well to a prophylactic, or preventive, treatment with narrowband UVB phototherapy, a common treatment for certain skin disorders.

“Although it is apparently a milder disease than early‐onset EPP, the affected patients actively pursued medical help,” the scientists wrote. “Thorough evaluation and treatment are warranted as for any type of EPP.”

Researchers noted their study had several limitations, including its small number of included studies and a literature search restricted to articles written in English.

Nonetheless, their review showcased “the distinct features of IGLO [inherited genetic late-onset] EPP,” and highlighted “that a diagnosis of inherited genetic EPP should not be ruled out in adults with new‐onset photosensitive manifestations.”