Acute Intermittent Porphyria Presenting with Central and Peripheral Nervous System Involvement: First Report of the HMBS c.770T>C (p.Leu257Pro) Variant in a Chinese Patient

Background Acute intermittent porphyria (AIP) is a rare autosomal dominant disorder. Clinically, it typically presents with acute neurovisceral attacks in which severe abdominal pain is prominent. Notably, neurologic involvement may dominate the clinical picture. Definitive diagnosis rests on genetic confirmation of pathogenic HMBS variants. Because of its protean clinical profile, diagnosis and management are challenging, and cases dominated by neurologic symptoms are often misclassified.. Case presentation: We present a case of a 20-year-old female with recurrent severe abdominal pain, progressive quadriplegia, hyponatremia, and neuropsychiatric disturbances. Genetic testing confirmed the diagnosis of AIP and identified a heterozygous mutation in the HMBS gene (c.770T > C, p.Leu257Pro). Clinical improvement was observed following heme infusion, high-carbohydrate therapy, and structured rehabilitation. Conclusions In patients presenting with unexplained abdominal pain accompanied by neuropsychiatric symptoms and hyponatremia, a high index of suspicion for AIP is warranted. Prompt metabolic and genetic testing facilitates early confirmation of the diagnosis, thereby helping to prevent irreversible neurological damage. The heterozygous HMBS gene mutation c.770T > C (p.Leu257Pro) identified in this AIP patient represents the first reported case in the Chinese population. The concurrent involvement of both the central and peripheral nervous systems suggests potential population specificity and phenotypic severity.