BACKGROUND: Acute intermittent porphyria (AIP) is an inherited metabolic disorder that can affect the central, peripheral, and autonomic nervous systems. Therefore, its clinical presentation is diverse and may include abdominal pain, as well as neurological and psychiatric symptoms. Abdominal pain, though a common initial symptom, is often overlooked or misdiagnosed due to its lack of specificity. But early diagnosis and treatment are crucial, as untreated symptoms can progressively worsen. CASE PRESENTATION: This report describes a 26-year-old male who was admitted due to seizures and PRES changes on brain magnetic resonance imaging (MRI) for over 30 days, along with a 20-day history of sudden proximal weakness in both upper limbs. Additionally, he experienced recurrent vomiting and excessive sweating. Five months before admission, he was diagnosed with a urinary tract infection due to severe abdominal pain and tea-colored urine, and the symptoms resolved after treatment. Multiple examinations before and after admission consistently revealed hypertension, tachycardia, and hyponatremia. Electromyography (EMG) suggested axonal damage to the motor nerves of both upper limbs. During hospitalization, the patient's upper limb weakness progressively worsened, and around 12 days after admission, he began experiencing recurrent episodes of abdominal pain and limb pain. Then he was diagnosed with AIP based on the detection of positive PBG in urin and the identification of a c.445C >
T (R149X) mutation in the hydroxymethylbilane synthase (HMBS) gene. CONCLUSIONS: This case unveils that AIP is a disease that can be easily overlooked in its early stages. When a patient presents with central, peripheral, or autonomic nervous system symptoms and common causes are ruled out, AIP should be considered as a potential diagnosis. Additionally, unexplained symptoms such as abdominal pain, changes in urine color, hyponatremia should also raise suspicion. Timely screening through biochemical testing, including measurement of ALA, PBG and porphyrins in a random urine sample, is recommended. Timely administration of intravenous hemin and avoidance of precipitating factors can lead to a better prognosis.