Remember that Many Commonly used Intensive Care Unit Drugs Should not be Used in Porphyria
J. Gregory Hobelmann MD
The porphyrias are a constellation of congenital and acquired deficiencies in the activity of enzymes involved in the biosynthesis of heme. Abnormal amounts of the heme intermediate compounds are formed, resulting in tissue accumulation and excessive excretion. All of these intermediates in the heme biosynthetic pathway can be toxic and can result in neurovisceral symptoms or photocutaneous symptoms. Some porphyrias cause life-threatening neurovisceral abnormalities and are characterized by the presence of aminolevulinic acid (ALA) or porphobilinogen in the urine. Others cause photosensitivity and skin damage with exposure to ultraviolet light with subsequent production of tissue-damaging free radicals.
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The diagnosis of each type of porphyria may be made by identifying the metabolite of excess in the urine, feces, or blood. The two most common types are porphyria cutanea tarda and acute intermittent porphyria. The diagnosis of porphyria cutanea tarda is strongly suggested by the presence of blistering skin lesions on areas exposed to ultraviolet light. This condition is confirmed by a high plasma porphyrin level and uroporphyrin in the urine. Liver enzymes may be elevated, but liver function is rarely affected. Risk factors for developing porphyria cutanea tarda include excessive alcohol use, hepatitis C, human immunodeficiency virus (HIV), and iron overload. Treatment consists of phlebotomy and low-dose chloroquine, which are almost always effective. Other than potential cutaneous scars, there are no long-term sequelae of the disease. Care must be taken to pad the skin during hospital care to avoid further damage.