A Four-Year Diagnostic Journey to Acute Intermittent Porphyria in a 19-Year-Old Woman: Lessons on Recognizing...

Acute intermittent porphyria (AIP) is a rare autosomal dominant metabolic disorder caused by hydroxymethylbilane synthase (HMBS) deficiency, resulting in the accumulation of neurotoxic porphyrin precursors. Its rarity and overlap with psychiatric, neurological, and gastrointestinal clinical features frequently lead to diagnostic delays and substantial morbidity. Therefore, we report the case of a 19-year-old woman who presented to a UK tertiary hospital with recurrent tonic-clonic seizures and severe episodes of abdominal pain over a four-year period. After initial investigations excluded cardiac and epileptic causes, she was diagnosed with pseudoseizures and referred to a psychiatric facility because no conclusive epileptiform activity was detected on electroencephalography (EEG). Multiple gastrointestinal diagnostic investigations, including gastric emptying studies, were unsuccessful in identifying an underlying cause. Following postoperative deterioration characterized by nausea, vomiting, and seizures, porphyria screening was initiated. Fecal total porphyrins were elevated at 72.3 nmol/g (reference range, 0-49.9 nmol/g), raising strong biochemical suspicion of an acute hepatic porphyria and prompting specialist referral, while plasma and urinary porphyrin levels remained within normal limits. The patient was referred to a specialist porphyria clinic for genetic confirmation and management. This case illustrates the diagnostic complexity of AIP, in which overlapping neurological and psychiatric features can frequently result in misdiagnosis, and demonstrates that fecal porphyrin elevation can provide valuable complementary biochemical evidence when other investigations are inconclusive, particularly when testing is performed outside an acute episode. AIP should therefore be considered in young women with recurrent unexplained seizures and abdominal pain, especially when standard investigations, including urinary aminolevulinic acid (ALA) and porphobilinogen (PBG), are unremarkable, as normal urinary ALA and PBG levels measured outside an acute attack do not exclude AIP. Early metabolic screening, including fecal porphyrin analysis, may prevent years of morbidity and facilitate timely specialist referral.