BACKGROUND: Acute porphyria and Arnold Chiari malformation are both uncommon genetic disorders without known association. The insidious onset, non-specific clinical manifestations, and precipitating factors often cause diagnosis of acute porphyria to be missed, particularly in patients with comorbidities.

CASE REPORT: A women with Arnold Chiari malformation type II who was treated with oxybutynin and antibiotics, including Bactrim for neurogenic bladder and recurrent urinary tract infection, presented with non-specific abdominal pain, constipation, and diarrhea. After receiving Flagyl for C. difficile colitis, the patient developed psychosis, ascending paralysis, and metabolic derangements. She underwent extensive neurological workup due to her congenital neurological abnormalities, most of which were unremarkable. As a differential diagnosis of Guillain Barré syndrome, acute porphyria was then considered and ultimately proved to be the diagnosis. After hematin administration and intense rehabilitation, the patient slowly recovered from the full-blown acute porphyria attack.

CONCLUSIONS: This case report, for the first time, documents acute porphyria attack as a result of a sequential combination of 3 common medications. This is the first case report of the concomitant presence of both acute porphyria and Arnold Chiari malformation, 2 genetic disorders with unclear association.

Keywords: Arnold-Chiari Malformation - therapy, Diagnosis, Differential, Guillain-Barre Syndrome - diagnosis, Porphyria, Acute Intermittent - therapy