Name: Dersimelagon (MT-7117) in Erythropoietic protoporphyria or X-linked protoporphyria: Diagnosis
Published: 2026-09-21T21:42:40-04:00

Erythrocyte protoporphyrin with metal-free and zinc fractionation as the recommended test

“Total erythrocyte protoporphyrin concentration, including proportions of metal-free and zinc-bound protoporphyrin, is the recommended test for the diagnosis of protoporphyria” (opens the source at this quote in a new tab)
“The percentage of metal-free protoporphyrin is typically >90% in EPP and ~50–85% in XLP.” (opens the source at this quote in a new tab)

“Detection of markedly increased free erythrocyte protoporphyrin is the most sensitive and specific biochemical diagnostic test for EPP” (opens the source at this quote in a new tab)
“It is important to evaluate by using an assay that distinguishes free protoporphyrin from zinc-chelated protoporphyrin” (opens the source at this quote in a new tab)

Diagnostic threshold and biochemical discrimination of the two disorders

“A metal‐free PPIX ≥3 times the upper limit of normal (ULN) establishes the diagnosis of protoporphyrias.” (opens the source at this quote in a new tab)
“Therefore, XLEPP can usually be distinguished biochemically from EPP1 by the higher proportion of ZnPP.” (opens the source at this quote in a new tab)

Commercial assays that measure zinc protoporphyrin can miss the diagnosis

“Some major commercial labs, such as Quest and LabCorp, provide a “free erythrocyte protoporphyrin” test, which is actually a zinc protoporphyrin test.” (opens the source at this quote in a new tab)
“Because zinc protoporphyrin is often normal in EPP, the diagnosis may be missed.” (opens the source at this quote in a new tab)

Genetic testing to distinguish the two disorders

“If a diagnosis of protoporphyria is established based on significantly elevated protoporphyrin, genetic testing of the FECH and ALAS2 genes is recommended to distinguish between EPP and XLP.” (opens the source at this quote in a new tab)

Diagnostic delay

“The mean diagnostic delay is over a decade, and evidence supports significant underdiagnosis.” (opens the source at this quote in a new tab)

“The mean number of years between initial symptoms and diagnosis of EPP was 13 years” (opens the source at this quote in a new tab)
“The majority (76%) presented with symptoms of EPP before four years of age” (opens the source at this quote in a new tab)
“Holme et al identified 389 patients with EPP in the UK; the median ages at symptom onset and diagnosis were one and 12 years, respectively.” (opens the source at this quote in a new tab)
“Wahlin et al identified 51 patients with EPP in Sweden; the median ages at onset and diagnosis were one and 22 years.” (opens the source at this quote in a new tab)

“The median delay in diagnosis from the onset of symptoms was 4.0 years (range 0-36), and 28 patients (80%) experienced a delay of 1 or more years” (opens the source at this quote in a new tab)

“Mean age at diagnosis was 28 years, with only 22 patients (12.2%) diagnosed ≤10 years old.” (opens the source at this quote in a new tab)

Misattribution of symptoms before diagnosis

“Thirty eight percent of patients saw five or more physicians prior to being diagnosed with EPP; of those, 22% saw more than 10 physicians.” (opens the source at this quote in a new tab)
“Prior to diagnosis, the majority of individuals were thought to have a sun allergy (50%), or another type of allergic reaction (16%); 15% of individuals were thought to have a psychological issue.” (opens the source at this quote in a new tab)