Erythropoietic Protoporphyria (EPP)

ICD-11

AIB2.0; AIB2.1

Synonyms

Disturbance of haem biosynthesis.

Epidemiology

Very rare. Symptoms (light sensitivity) starting early in life (10 years); Incidence 1:100 000.

Definition

Chronic polyetiologic disturbance of the haem-(porphyrin) biosynthesis in the erythrocytes, leading to accumulation of photosensitive porphyrins in the skin and other organs.

Aetiology & Pathogenesis

Autosomal-recessive inherited mutation, usually in the ferrochelatase (FECH) -gene.

The reduced mounting of iron-iones in the hemoglobine of the erythrocytes leads to accumulation of its precursor protoporphyrin. Light sensitivity in the long wave UVA (400nm, Soret-band).

Signs & Symptoms

Acute: Burning (not itching) of the skin upon sun exposure, also through window glass or front shield of the car, which filters only UVB but not the pathogenetically important UVA.

Acute erythema and edema in the light exposed areas (face, hands, lower arms). Never blistering.

Permanent chronic changes: cerebriform lichenification and thickening of the skin, especially on the back of the nose, margins of the conch of the ear, back of hands and fingers.

Urine: normal color, since protoporphyrine is not water soluble and therefore is excreted through the stool.

Localisation

Face, back of the nose, margins of the conch of the ear, back of hands and fingers. Sun exposed areas.

Classification

Hepatic porphyrias

Prototype: porphyria cutanea tarda: sporadic, genetic/familiar, toxic

Erythropoietic porphyrias

Erythropoietic prtoporphyria
Congenital erythropoietic porphyria (Günther)

Laboratory & other workups

Diagnostic rapid test: red fluorescence of some (30%) of erythrocytes in a blood smear under the fluorescence microscope (blue light excitation). Cave: quick fading. The blood smear should be handled in a dark room.

Urine: negative, since protoporphyrine is not water soluble.

Stool: qualitative and quantitative determination of protoporphyrin (special laboratory).

Determination of the defective enzymes.

Dermatopathology

Acute: dermal edema; chronic: lichenification; perivascular PAS positive deposits.

Course

Acute and relapsing with chronic sequelae.

Complications

Limitation of the open-air mobility; accusation of hypochondric behaviour.

Diagnosis

Typical clinical features; confirmation by laboratory tests.

Differential diagnosis

Other photodermatoses without blisters. Never blisters in erythropoietic protoporphyria.

Prevention & Therapy

Topical: Light protection (SPF/LSF > 30). Cave: Vitamin D-deficiency due to lack of vitamin-D production in the skin by UV.

Photoprotection against long wave UVA; beta-carotene; afamelanotide.

6.2.3 Erythropoietic Protoporphyria (EPP)