紫質症(porphyria)是種罕見疾病,造成疾病的主要原因是合成血基質的酵素活性異常,致使患者體內的紫質或其前驅物在體內過量堆積,進而對人體造成毒性。依照臨床症狀的不同,紫質症可大致分為三種,本案例討論的是其中最嚴重的急性間歇性紫質症(acute intermittent porphyria, AIP)。病因是製造合成血色素(heme)的第三個酵素,porphobilinogen deaminase (PBGD)的基因產生突變,造成酵素活性不足,進而使血色素的前驅物 porphobilinogen (PBG)及 aminolevulinic acid (ALA)堆積過多而致病。此病雖屬顯性遺傳疾病,然而有九成左右帶有缺陷基因者,並不會發病,直到某些促發因子誘使 AIP 急性發作。腹痛(廣泛性或局部性)是最常見的症狀,且合併神經及精神方面的症狀(包括周邊神經病變、自主神經病變、中樞神經病變、心智狀態改變等)。藥物本身就是誘發 AIP 的危險因子之一,因此藥物治療更須謹慎選擇。急性發作時,可每日靜脈注射 400 g dextrose 1 至 2 天,若改善情況不佳,再靜脈注射 human hemin 連續 4 天。本案例描述一位經年酗酒的男性病人,自數年前即常因間歇性腹痛而住院,始終查不出病因,本次住院仍反復發作腹痛、抽筋、意識不清等神經及精神症狀。經檢測出尿液中 porphobilinogen(PBG) ,δ-aminolevulenic acid (D-ALA)的含量過高而證實為急性間歇性紫質症。

    Porphyria is a rare disease caused by deficiency of various specific enzymes in the biosynthesis of heme. Porphyria can be divided into 3 subtypes according to the enzymes in deficit. Acute intermittent porphyria (AIP) is an autosomal dominant deficiency in porphobilinogen deaminase. This results in an excessive production of the heam precursors aminolevulinic acid (ALA) and porphobilinogen (PBG). Most individuals remain clinically latent until a precipitating factor triggers an acute attack. The main clinical features of an attack are gastrointestinal disturbance and neuropsychiatric disorders. The most common symptom is abdominal pain, which is usually steady and poorly localized and may be cramping. Patients may present with peripheral neuropathy, autonomic dysfunction, altered mental status, and seizures. Drug is an important cause of AIP attacks. The impact of most drugs on this diaease has not been determined. Heme therapy and carbohydrate loading are specific therapies for this disease through repress hepatic ALA synthase and over production of ALA and PBG. Heme therapy is the therapy of choice and should be initiated early. A 37-year-old male patient had been suffering from intermittent abdominal pain since he was young, especially after alcohol drinking. He was hospitalized for several times, but did not find the cause. This time, he was admitted to urology ward due to sudden onset of diffuse abdominal pain with gross hematuria. After admission, elevated liver function, hyponatremia, conscious disturbance (delirium, visual hallucination) and seizure were noted, and AIP was suspected then a diagnosis of AIP was made according to the high content of urinary PBG and ALA .