P. Treadwell et al. (eds.)Atlas of Adolescent Dermatologyhttps://doi.org/10.1007/978-3-030-58634-8_21

21. Erythropoietic Protoporphyria

Julie Prendiville¹

(1)

Department of Pediatrics, University of British Columbia, Vancouver, BC, Canada

Julie Prendiville

Email: jprendiville@sidra.org

Keywords

PorphyriaProtoporphyrinPhototoxicBetacaroteneAlfamelanotide

21.1 Introduction

Erythropoietic protoporphyria (EPP) is a rare genetic disorder of heme biosynthesis characterized clinically by acute pain on sun exposure.

21.2 Epidemiology

EPP is the most common porphyria of childhood. It may present or be first diagnosed in adolescence.

Inheritance is autosomal recessive. It is caused by a combination of loss of function mutations and low expression allelic variants in the FECH gene. Deficiency of the enzyme ferrochelatase leads to accumulation of protoporphyrin IX in circulating erythrocytes. Following exposure to sunlight, these protoporphyrins cause acute cutaneous phototoxicity. Accumulation of protoporphyrins in the liver may result in hepatotoxicity and cholestasis.

X-linked protoporphyria, caused by mutations in ALAS2, has a similar clinical presentation to EPP.

21.3 Clinical Findings

Symptoms occur shortly after sun exposure, most commonly on the face, dorsal hands, arms, and feet. Objective clinical findings are often absent despite excruciating pain. Variable erythema and edema may be observed (Fig. 21.1). Erosions and crusting of the skin are uncommon. Chronic atrophic changes on the face or dorsal hands may result from severe phototoxic reactions or recurrent sun exposure.

../images/446896_1_En_21_Chapter/446896_1_En_21_Fig1_HTML.jpg — Fig. 21.1
Erythema of dorsal hands in EPP

21.4 Laboratory

Laboratory investigation shows elevated levels of free erythrocyte protoporphyrin. The diagnosis may be confirmed by sequencing of the FECH (or ALAS2) gene. Patients require monitoring for liver dysfunction, anemia, and vitamin D deficiency.

21.5 Treatment

Sun avoidance is the mainstay of treatment. A UV meter may be helpful to indicate the times and months when protective clothing, hats, gloves, umbrellas, and tinted windows are required. Topical sunscreens are of limited benefit. Oral betacarotene and alfamelanotide have been reported to improve sun tolerance.

21.6 Prognosis

Social isolation and lifestyle changes may significantly impair quality of life. A small subset of patients have severe progressive liver disease.