History
A 16-year-old boy with scarring over his face is referred to the dermatology out-patient clinic. He reports a history of burning and stinging of his skin (especially his nose) whilst outside playing football. On direct questioning his parents recall as a small child he would cry after a few minutes of sun exposure. His parents had also noted his skin would then turn red and blister. Consequently, as a young child they tried to keep him out of the sun as much as possible. However, as a teenager keen on sports he has recently noticed a deterioration of the skin on his face. He is otherwise well and takes no medication.
Examination
Over his cheeks and nose the skin appears waxy and atrophic with multiple areas of pitted scarring (Fig.18.1). Areas of hyperpigmentation and milia are seen on the dorsal aspects of his hands.
Questions
• What is the underlying diagnosis?
• How might you confirm this?
• What other diseases may be associated?
Medicine
This patient has erythropoietic protoporphyria (EPP) which is a rare, hereditary autosomal-dominant metabolic disorder of porphyrin metabolism. Patients usually report symptoms starting in early childhood. Photosensitivity may be severe with almost immediate sting-ing, burning and itching following sun exposure. Erythema, oedema, vesicles and purpura appear within 1–8 hours predominantly over the nose, cheeks and dorsi of the hands.
Similar symptoms can occur when a person is exposed to sunlight through window glass.
Over time these areas develop into shallow, atrophic and often linear scars. Diffuse wrin-kling of the skin on the nose, cheeks and perioral area can also occur leaving a waxy appearance. The skin over the metacarpal phalangeal joints can become indurated and shiny (‘aged knuckles’).
EPP results from a deficiency in the enzyme ferrochelatase. This defect occurs at the step in porphyrin metabolism where protoporphyrin is converted to haem by ferrochelatase, deficiency of which leads to a high accumulation of protoporphyrin which is highly pho-tosensitizing. Red blood cells (RBC) and faeces show increased levels of protoporphyrins.
Fresh RBCs fluoresce coral red when examined in a dark room under ultraviolet light.
Approximately 10 per cent of patients with EPP may have underlying haemolytic anae-mia, hypersplenism and cholelithiasis (including in young children). Associated liver disease is common, but fortunately rarely leads to fatal hepatic failure requiring hepatic transplantation.
Management includes education concerning photoprotective measures to prevent expo-sure to ultraviolet and visible light. Patients should avoid any unnecessary exposure to sunlight and should wear photoprotective clothing / wide-brimmed hat. If possible, tinted windows should be installed. Patients / medical practitioners should remember that other strong sources of light can also trigger symptoms, including indoor fluorescent and halogen lights. Patients with EPP should have strict photoprotection of their skin during surgical procedures, as operating lights can trigger severe attacks. Oral -carotene can be effective in some patients in reducing photosensitivity.
KEY POINTS
• EPP is a rare, hereditary autosomal dominant disorder of porphyrin metabolism.
• Patients usually present in childhood with photosensitivity.
• The mainstay of management is photoprotection.
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