Diagnosis: Erythropoietic protoporphyria
Erythropoietic protoporphyria (EPP) is a metabolic disease that is caused by a deficiency in ferrochelatase enzyme activity.1,2 Ferrochelatase is the last enzyme in the heme biosynthetic pathway, which is responsible for the incorporation of iron onto protoporphyrin IX.1 Ferrochelatase activity in patients with EPP is typically 10% to 25% of normal, resulting in an accumulation of protoporphyrin IX in the skin, erythrocytes, liver, and plasma.1,3 There are both autosomal dominant and recessive forms of EPP, and it is the most common porphyria found in children.1,3
A characteristic that distinguishes EPP from other porphyrias is the rapid onset of photosensitivity associated with pruritus and a stinging or burning sensation on the sun-exposed areas of the body—typically, the cheeks, nose, and dorsal surface of the hands.4 These symptoms are commonly followed by edema, erythema, and in more severe cases, petechiae.3,4 With repeated sun exposure, the affected skin may develop a waxy thickening with shallow linear or elliptical scars, making the patient’s skin appear much older than it actually is.3,4 Although blisters, erosions, and crusting are not always present, they can manifest with prolonged sun exposure.1
What you may also see
Hepatobiliary disease is present in about 25% of patients, and may be the only manifestation of the disease.1 The deleterious effects of protoporphyrin are concentration dependent, so a wide variation in the severity of hepatobiliary disease exists. Cholelithiasis and micro-cytic hypochromic anemia are common on the mild end of the spectrum, but life-threatening complications such as hepatic failure have been reported in about 2% to 5% of cases.1,5
When it’s diagnosed. EPP usually manifests by 2 to 5 years of age, but it may not be diagnosed until adulthood.3 Such a delay may occur because of a lack of cutaneous lesions, mild symptoms, or a late onset of symptoms.1
Consider these conditions in the differential
Contact dermatitis. This inflammatory skin condition can occur when a foreign substance irritates the skin (irritant contact dermatitis) or result from a delayed hypersensitivity reaction that’s evoked by reexposure to a substance (allergic contact dermatitis). Acute lesions are typically well defined and confined to the site of exposure. They are characterized by erythema, vesicles or bullae, erosions, and crusts. In chronic cases, the lesions are ill-defined and involve plaques, fissures, scaling, and/or crusts.4,6