Acute Hepatic Porphyria

A rare sub-group of porphyrias characterized by the occurrence of neuro-visceral attacks with or without cutaneous manifestations. Acute hepatic porphyrias encompass four diseases: acute intermittent porphyria (the most common), variagate porphyria, hereditary coproporphyria, and hereditary deficit of delta-aminolevulinic acid dehydratase (extremely rare).

Epidemiology

In the majority of European countries, the prevalence of acute hepatic porphyrias is around 1/75,000. In 80% of cases the patients are female, with the majority aged between 20 to 45 years.

Clinical description

All acute hepatic porphyrias can be accompanied by neuro-visceral attacks that appear as intense abdominal pain (in 85-95% of cases) over one to two weeks, neurological symptoms (muscular weakness, sensory loss or convulsions) and psychological symptoms (irritability, anxiety, auditory or visual hallucinations, mental confusion). The attacks are most commonly triggered by exogenous factors (porphyrinogenic medicines, alcohol, infections, a hypo-calorific diet, stress), and/or endogenous factors (hormonal, linked to menstrual cycle). Cutaneous lesions are present in the majority of patients affected by variagate porphyria and in less than 15% of patients with hereditary coproporphyria.

Etiology

Each acute hepatic porphyria is a result of a deficiency of one of the enzymes in the heme biosynthesis pathway. These deficiencies result in an accumulation of the precursors of porphyrins in the liver (delta-aminolevulinic acid, ALA and porphobilinogen, PBG) and also, in the case of variagate porphyria and hereditary coproporphyria, an accumulation of porphyrins resulting in cutaneous manifestations.

Diagnostic methods

Diagnosis is based on evidence of elevated concentrations of ALA and especially PBG (pathognomic) and, sometimes, of porphyrins in urine, stools or plasma. The type of porphyria is defined by enzyme measurement followed by the correspondent characterization of the mutations of DNA.

Differential diagnosis

Differential diagnoses include Guillain-Barré syndrome (see this term) and all causes of acute abdominal pain. Differential diagnoses for variagate porphyria and hereditary coproporphyria also include photosensitivity.

Genetic counseling

Acute hepatic porphyrias are monogenic hereditary disorders that are transmitted in an autosomal dominant manner (except the hereditary deficit of delta-aminolevulinic acid which is autosomal recessive). Genetic counseling should be offered to patients and their families to identify individuals susceptible to developing or transmitting the disease.

Management and treatment

When an acute attack is confirmed, urgent treatment with an injection of human hemin and/or perfusion of carbohydrates is required. Management includes the prevention of attacks (by avoiding causal factors) and the protection of skin from the light in cases of cutaneous manifestations.

Prognosis

In certain patients attacks recur, resulting in the need for repeated and more frequent injections of human hemin. Crippling attacks can possibly indicate a hepatic transplant. However, in the majority of cases, the disease remains asymptomatic during all adult life and it is rarely progressive.