Porphyria. This post will cover the points you need to know for your board exams as well as for teaching residents on the daily rounds. Please don't use the information here to treat your patients.
Porphyria is a group of conditions that occur due to build up of porphyrins in various body organs and parts due to certain enzyme deficiency in the heme pathway. Depending on the primary symptoms, it is classified into Acute hepatic porphyrias (AHP) and Cutaneous porphyrias.
AHPs, including acute intermittent porphyria (AIP), hereditary coproporphyria (HCP), variegate porphyria (VP), and ALA-dehydratase deficiency porphyria (ALD) typically present with sudden attacks of severe stomach pain, among other symptoms (like mental changes, seizures, dark urine, muscle pain, palpitations) which last for several days; VP and HCP may also have skin symptoms of blistering after sun exposure.
The cutaneous porphyrias present with blistering and scarring of the skin, pain, and/or redness and swelling in sun-exposed areas.
Most porphyria has genetic predisposition except for Porphyria cutanea tarda (PCT) which is usually precipitated by a stressor like alcohol abuse, smoking, hormonal changes, hemochromatosis and viral infections (like Hepatitis C and HIV). Other risk factors for porphyria in general includes drugs, sunlight exposure, surgery and medications.
List of medications that can precipitate acute porphyria attacks include:
1- Barbiturates like phenobarbital and butalbital.
2- Antiseizure medications like phenytoin (Dilantin) and fosphenytoin.
3- Trimethoprim An antibiotic commonly used for urinary tract infections.
4- Reproductive Hormones: Progesterone and related steroids should be used with caution.
Acute porphyria can be tested by urine porphobilinogen (PBG) test, this is different than a test looking for urine total porphyrins.
Blistering skin symptoms suggestive of PCT, CEP, HEP, VP, or HCP—a blood test called plasma total porphyrins, and a urine total porphyrins test.
Non-blistering skin symptoms suggestive of EPP or XLP—the blood tests plasma total porphyrins and erythrocyte protoporphyrins.
Main treatment is avoiding triggers.
Treatment of acute porphyria includes Injections of hemin (Panhematin),Receiving fluid that contains sugar and Givosiran (Givlaari).
Treatment of cutaneous porphyrias focuses on reducing exposure to triggers such as sunlight. Reducing porphyrins may include phlebotomy, hydroxychloroquine (Plaquenil). This can help absorb excess porphyrins and help your body get rid of them more quickly than usual. The medicine is generally used only in people who can't tolerate phlebotomy.
Replace low vitamin D levels caused by avoiding sunlight.
High doses of beta carotene are a common treatment for erythropoietic protoporphyria.
For erythropoietic protoporphyria afamelanotide skin implant (Scenesse) maybe used which increases melanin in the skin reducing the sunlight effects.
Interesting book on the topic is Porphyria.
The information in this post is not for patients and shouldn't be used in treating patients. Please refer to your doctor for medical advice.