On Saturday, October 18, on the opening evening of the American Society of Human Genetics (ASHG) 2014 annual meeting in San Diego, California, Robert J. Desnick, M.D., Ph.D., the Dean for Genetics and Genomics at the Mt. Sinai School of Medicine, in New York City, had the pleasure of reporting the largely positive results of the phase III clinical trials of the 16 mg subcutaneous bioresorbable implants of afamelanotide for the treatment of the excruciatingly painful, extremely rare, autosomal recessive skin disease known as erythropoietic protoprhyria (EPP), or popularly as “popcorn ichthyosis.” The skin of patients with this genetic condition is severely sensitive to light (which is phototoxic) and the result is intolerable pain, swelling, and scarring, usually of the exposed areas such as the face, hands, and feet. The pain experienced and expressed by EPP patients when their skin is exposed to light is reported as intolerable. Dr. Desnick explained that there is presently no effective treatment except for avoiding the sun and patients are called “shadow jumpers.” EPP is characterized by abnormally elevated levels of protoporphyrin IX in erythrocytes and plasma, and by sensitivity to visible light that is usually noticed in early childhood and occurs throughout life. EPP can result either from mutations of the ferrochelatase gene (FECH), or less commonly of the delta-aminolevulinic acid synthase-2 gene (ALAS2). When EPP is due to an ALAS2 mutation it is termed X-linked protoporphyria (XLP), because that gene is found on the X chromosome.
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