Mary, living with a type of porphyria


Understanding Porphyria

Porphyrias are a group of rare, most often inherited, disorders caused by a defect in the pathway that makes heme in your body. Heme, a cofactor, is a nonprotein part of hemoglobin, which is responsible for transporting oxygen in blood, and is required for the normal function of some proteins in the liver. The types of porphyria are often grouped into those that predominantly affect the nerves and those that primarily affect the skin. Effects on nerves can occur in the acute hepatic porphyrias (AHP)—acute intermittent porphyria (AIP), variegate porphyria (VP), hereditary coproporphyria (HCP), and ALAD-Deficient Porphyria (ADP)—which are characterized by episodes of debilitating attacks.

Approximately 5,000 affected individuals in the United States and Europe experience acute porphyria attacks annually, and approximately 1,000 people are impacted by recurrent debilitating attacks. Currently, there is no approved treatment available to prevent recurrent attacks. Common treatment approaches for AHP include carbohydrate loading, intravenous (IV) glucose, and IV hemin, which can be administered during an attack or sometimes between attacks (prophylactically). However, hemin is not currently approved for the prophylactic treatment of AHP and has limitations.

What are the symptoms of acute hepatic porphyria?

Affected individuals often experience some combination of the following symptoms:

Autonomic Nervous System Injury
  • Severe pain in the abdomen, chest, back, extremities
  • Nausea, vomiting, bloating
  • Sweating, hypertension, elevated heart rate
Peripheral Nervous System Neuropathy
  • Weakness
  • Numbness
  • Paralysis
  • Difficulty breathing
Central Nervous System Neuropathy
  • Confusion
  • Anxiety
  • Hallucinations
  • Seizures
Cutaneous Findings (HCP and VP only)
  • Increased skin fragility
  • Lesions after exposure to sunlight
  • Increased scarring

What causes acute hepatic porphyria?

  • In people with acute hepatic porphyria:

    • 1 of the 8 enzymes in the pathway is deficient and works at ~50% of normal activity
  • This deficient enzyme activity level is still adequate in most circumstances
  • Certain triggers can induce ALAS1, leading to increased flow through the heme pathway and the buildup of ALA and PBG, the toxic intermediates thought to cause nerve injury and porphyria symptoms

ALAS1 = 5-aminolevulinate synthase 1; ALA = aminolevulinic acid; PBG = porphobilinogen; HMB = hydroxymethylbilane; UroIII = uroporphyrinogen III; Copr = corproporphyrinogen III; PP’genIX = protoporphyrinogen IX; PPIX = protoporphyrin IX.

Meet Rose & Colin

“I live my life around treating that pain…I don’t even know how to talk about it.”

These are Rose & Colin’s stories about living with porphyria.

Rose and Colin – Living with Porphyria


Interested in learning about our porphyria studies? Get started here.

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At Alnylam, we put you at the center of everything we do. We have a team dedicated to collaborating with patient advocacy groups and individuals affected by these rare diseases.

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  1. Balwani M, Desnick RJ. The porphyrias: advances in diagnosis and treatment. Blood. 2012;120(23):4496-4504.
  2. Anderson KE, Bloomer JR, Bonkovsky HL, et al. Recommendations for the diagnosis and treatment of the acute porphyrias. Ann Intern Med. 2005;142(6):439-450.
  3. Bissell DM, Wang B. Acute hepatic porphyria. J Clin Transl Hepatol. 2015;3(1):17-26.
  4. Bonkovsky HL. Neurovisceral porphyrias: what a hematologist needs to know. Hematology Am Soc Hematol Educ Program. 2005:24-30.
  5. American Porphyria Foundation. Acute Intermittent Porphyria (AIP). http://www.porphyriafoundation.com/about-porphyria/types-of-porphyria/AIP.
  6. EPNET—The Porphyria Consortium. http://porphyria.eu/en/content/introduction-porphyria


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