Porphyria

Definition

Porphyria is a group of inherited disorders involving abnormalities in the production of heme pigments (the base material responsible for hemoglobin (red blood cell pigment), myoglobin (reddish muscle cell pigment), and another group of materials called cytochromes.

Porphyrias are characterized by 3 major findings: photodermatitis (light sensitivity causing rashes), neuropsychiatric complaints, and visceral complaints (such as abdominal pain or cramping).

Causes, incidence, and risk factors

The porphyrias may be inherited as either autosomal dominant (caused by inheriting 1 abnormal copy of the gene) or autosomal recessive (requires inheritance of 2 abnormal genes) traits, depending on which type of porphyria is involved. Some types of porphyria begin in early childhood, some at puberty, and others begin during adulthood.

A classical attack of acute porphyria generally begins with colicky abdominal pain (severe), and is then followed by vomiting and constipation. Personality changes may develop during an acute attack, in addition to peripheral paresthesia (numbness and tingling), weakness, paralysis, sensory changes, and muscle pain. Acute attacks can be life-threatening, producing severe electrolyte imbalances, low blood pressure, and shock.

Urine may become red or brown following an attack. Exposure to sunlight can cause reddening, pain, sensations of heat, blistering, and edema in the skin. These lesions heal slowly, often with scarring or pigment changes and may be disfiguring.

Symptoms

• Red urine
• Sensitivity to sunlight
• Blister (bulla) formation on exposure to sunlight
• Skin swelling (edema) on exposure to sunlight
• Photodermatitis
• Crampy abdominal pain (may be extremely severe)
• Constipation
• Vomiting
• Pain in the limbs
• Pain in the back
• Personality change
• Numbness or tingling
• Muscle pain
• Muscle weakness or paralysis

Signs and tests

• Tachycardia
• Loss of deep tendon reflexes
• Electrolyte changes (see chem-20) - hyponatremia
• Decreased kidney function as may be shown by the following tests:
  • Urinalysis
  • Serum creatinine
  • Creatinine clearance
  • BUN
  • Serum potassium
  • Arterial blood gases

• PROTO blood test (measures porphyrins in the blood)
• Enzyme assay for:
  • Uroporphyrinogen decarboxylase
  • Protoporphyrinogen oxidase
  • Porphobilinogen (PBG) deaminase
  • Coproporphyrinogen oxidase
  • ALA dehydratase
  • Uroporphyrinogen III cosynthase
  • Ferrochelatase

Treatment

During an acute attack, these treatments can be expected.

• Maintenance of electrolyte balance
• Monitoring of blood gasses
• Increase of carbohydrate intake (may be IV glucose solutions)
• Pain medication as needed
• Sedation for restlessness and agitation
• Propranolol for hypertension
• Intravenous hematin

• Avoid all alcohol
• Avoid drugs that may precipitate an attack
• Eat high carbohydrate diet
• Avoid sunlight
• Use sunscreen (if not contraindicated)
• Avoid skin trauma
• Beta-carotene
• Consider splenectomy

Expectations (prognosis)

The porphyrias are life-long intermittent illnesses, but with good long-term management, the affected person can expect long problem-free periods.

Complications

• Progressive muscle paralysis
• Respiratory failure
• Gallstones
• Disfigurement
• Coma

Calling your health care provider

Call your health care provider if you have any of the above symptoms suggestive of a porphyria. If you have already been diagnosed with a porphyria, call your health care provider at the first signs of an acute attack.

Prevention

Genetic counseling may be of benefit to prospective parents with a family history of any type of porphyria.

Illustrations

Porphyria cutanea tarda on the hands

Page Content:

Acute intermittent porphyria; Hereditary coproporphyria; Congenital erythropoietic porphyria; Erythropoietic protoporphyria ; acute intermittent porphyria; erythropoietic protoporphyria; congenital erythropoietic porphyria