INTRODUCTION

Acute intermittent porphyria (AIP, Swedish porphyria, pyrroloporphyria, intermittent acute porphyria) is an autosomal dominant disorder resulting from a partial deficiency of porphobilinogen deaminase (PBGD, hydroxymethylbilane synthase, previously called uroporphyrinogen I synthase), the third enzyme in the heme biosynthetic pathway (figure 1 and figure 2). Symptoms in AIP are due to effects on the visceral, peripheral, autonomic, and central nervous systems. They usually occur as intermittent attacks that are sometimes life-threatening [1,2].

The clinical manifestations and diagnosis of AIP will be reviewed here. The etiology, pathogenesis, and management of AIP and an overview of the porphyrias are discussed separately. (See "Etiology and pathogenesis of acute intermittent porphyria" and "Management of acute intermittent porphyria" and "Porphyrias: An overview".)

CLINICAL MANIFESTATIONS

Most individuals with acute intermittent porphyria (AIP, ie, those who inherit a porphobilinogen deaminase mutation) never develop symptoms. Accordingly, symptomatic disease may skip generations or be recognized in only one individual within a family. The presentation is highly variable and the symptoms are nonspecific, which accounts in part for delays in diagnosis. Symptoms usually occur as acute attacks, most often in the third or fourth decades of life, and are more common in women than in men. The most common manifestations of AIP are listed in the table (table 1).

Attacks in AIP develop over hours or days and persist for days or weeks, depending upon precipitating factors and treatment. There are no cutaneous manifestations. Rare exceptions are patients with AIP and advanced renal failure, who may develop elevations in plasma porphyrins and blistering skin lesions [2,3].

Abdominal and urinary symptoms — Abdominal pain is the most common symptom in AIP, occurring in 85 to 95 percent of patients with acute attacks (table 1). It is usually severe, steady, and poorly localized but is sometimes cramping, and is often accompanied by constipation and signs of ileus such as nausea, vomiting, abdominal distension, and decreased bowel sounds. However, diarrhea and increased bowel sounds are sometimes seen.