Unreported Skin Symptoms in EPP May Make Diagnosis Harder: Study

Most patients with rare porphyria seen to experience pain, swelling

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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Many of the symptoms of erythropoietic protoporphyria (EPP), a form of porphyria, may not be reported fully or at all, and this may make it harder to diagnose the rare disease, according to a new U.S. study.

Researchers observed that nearly all patients in the study manifested the burning pain and occasional swelling characteristic of the disorder.

But many also developed allodynia — experiencing pain from stimuli that aren’t usually painful — and a tingling known as paresthesia. Also commonly found among EPP patients were itching, known as pruritus, a reddening of the skin called cutaneous erythema, and fatigue.

“Recognizing these symptoms may aid in the identification of patients with this underdiagnosed disease,” the researchers wrote.

The study, “Light-Related Cutaneous Symptoms of Erythropoietic Protoporphyria and Associations With Light Sensitivity Measurements,” was published as a brief report in JAMA Dermatology.

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Light-Sensing Device May Help in Predicting EPP Symptoms

Many patients found to have unreported skin symptoms

EPP is caused by changes in the way the body processes a molecule called protoporphyrin. When protoporphyrin builds up in the skin, it reacts with sunlight and other sources of visible light.

This can lead to painful skin reactions that usually begin in early childhood and may persist for days.

This porphyria type is marked by skin hypersensitivity to sunlight and to some types of artificial light, like fluorescent lights. Yet, not all features of EPP are well-described in the literature, and some people may remain undiagnosed for several years.

“A better understanding and characterization of its light-induced cutaneous symptoms may aid in the identification of EPP,” the researchers wrote.

To add information to the literature, a team of researchers in the U.S. described the symptoms of a group of people with EPP. The team also noted how patients’ symptoms varied with the amount of light to which they were exposed.

The study included 35 adolescents and adults, ages 15 and older, with EPP. Participants had a mean age of 39.1 years, and 21 (60%) were female. They classified their skin tone as a three on a scale that ranged from one (lightest skin tone) to 12 (darkest skin tone).

The first symptoms for these patients appeared at a mean age of 2.9, in a range that went from birth to 8 years. Nearly all patients (97%) reported pain, a burning sensation, and tingling after they were exposed to a source of visible light.

Skin reactions felt “similar to being close to a flame” or “as if a magnifying glass is burning [the skin],” some patients said. Another patient said it felt like being “covered with boiling oil and being poked with 1,000 hot pins at the same time.”

Many (89%) reported allodynia, which was followed in frequency by pruritus or mild swelling (83%), scarring (66%), severe swelling (63%), and cutaneous erythema (51%).

Fewer than half developed scabbing or fatigue (46%), skin cracking (43%), round spots of bleeding under the skin (40%), and achiness (24%). In many (89%), symptoms improved with cold; in more than three-quarters (76%), visible skin reactions occurred hours to days after the onset of pain.

All patients experienced prodromal or early warning symptoms prior to the development of a full skin reaction. Warning symptoms included tingling (97%), pruritus (66%), and mild pain (43%). In two-thirds of patients (66%), these skin symptoms occurred within 30 minutes of exposure to sunlight.

Recognizing these symptoms may aid in the identification of patients with this underdiagnosed disease.

The 24 people who experienced symptoms at least once per week were asked to wear a light dosimeter, which is a device that measures exposure to light. They also were asked to complete text message surveys about their symptoms every day for one month, beginning in June through September.

Hands, feet, and face were the most light-sensitive body parts, whereas shoulders and legs were the least sensitive. In general, EPP symptoms did not vary with the amount of light to which people were exposed.

There were nine people (26%) who reported no chronic skin reactions and two (6%) who said they had never experienced any symptoms.

“Minimal skin changes or the absence of visible skin changes during reactions to light, including lack of erythema, do not exclude an EPP diagnosis nor suggest low EPP disease burden,” the researchers wrote.

“This information may facilitate a broader consideration of EPP as a possible diagnosis when appropriate. Additional studies are needed to understand the mechanisms of these EPP symptoms, an understanding that could inform the development of novel therapeutics,” the team concluded.