Publication Brief: Inherited genetic late-onset erythropoietic protoporphyria: A systematic review of the literature

Erythropoietic protoporphyria (EPP) is typically characterised by phototoxic reactions to visible light, commencing in early childhood (normally when a child is first exposed to environmental light). Yet, adult-onset cases of secondary EPP, and an even rarer and poorly investigated form, inherited genetic late-onset (IGLO), have also been reported.

In a recent systematic review, published in the journal Photodermatology Photoimmunology Photomedicine, Snast et al. discuss what is currently understood about IGLO EPP.

As background, it is important to differentiate between acquired EPP and IGLO EPP. Both can emerge at any age, and cases have been reported as late as 71 years old.  Acquired EPP is due to haematological disease and, in 80% of reviewed cases, the culprit was myelodysplastic syndrome (MDS), a form of cancer that can occur if the blood-forming cells in the bone marrow become abnormal. The presence of malignancy, and ability to identify a family member with EPP, are the two important steps in the differential diagnosis of IGLO vs acquired EPP.

As described in the review, and more widely by those living with EPP (see Photoprotection Network  for our Facebook community for light related disorders), patients experience acute episodes of phototoxicity – anaphylactoid reactions and burns after just a few minutes of exposure to visible light (including sun and artificial light); sometimes followed by erythema, erosions, and crusting. Additionally, accumulation of protoporphyrin IX within the liver and biliary system may lead to cholestasis and hepatic damage.

The systematic review found that IGLO has some distinct features. Notably, the phototoxic symptoms tended to be milder in severity compared with “classical” EPP, or acquired EPP. The main symptoms in IGLO EPP consist of itchiness (pruritus) and a rash on sun/light-exposed areas of skin.

Interestingly, the authors report a shorter delay to diagnosis of six years for the late-onset form, compared with 10-20 years in “classical” EPP. This, the authors hypothesised, was because the onset of symptoms later in life is unfamiliar to the patient and they experience a notable difference before and after symptom onset, prompting them to seek medical advice. Whereas in classical EPP, patients grow up alongside their condition, and adapt their behaviour accordingly.

The treatment and clinical care for all three classifications of EPP is the same.

In a final message, the authors warn that diagnosing physicians should not rule out the possibility of genetically inherited EPP if adults present with mild reactions to light/sun including pruritus and a rash, on sun-exposed areas of skin. To access the article in full, click here.

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