64-year old lady presented with sudden onset of flaccid tetraparesis and absent reflexes. Sensory deficit was non-dermatomal: affecting trunk, shoulders and buttocks. She was intolerant of multiple antibiotics and analgesics. Codeine dose was increased on admission. MRI whole spine was normal. 3 days later she developed increased drowsiness, intermittent apnoea, hypotension and tachycardia. CT brain was normal, EEG showed diffuse slowing. Deterioration was attributed to codeine (opiate) intoxication secondary to marked renal impairment. 5-days intravenous Naloxone infusion stabilized her breathing and blood pressure. Extensive fluid resuscitation facilitated renal function recovery. Improvement in limb weakness followed rapidly. Autonomic function tests were not performed. Medical notes revealed recurrent admissions with tetraparesis over period of 9 years. Probable diagnoses included recurrent cord ischaemia and GBS. MRI brain, spine and CSF examination were normal. Urine porphyria screening was positive 1 week post admission, although more consistent with latent porphyria (porphobilinogen 3.2 µmol/mmol creatinine; ref range <1.5). Genetic testing identified a novel mutation in HMBS gene—heterozygous sequence variant 1016C >T in exon 15 which replaces alanine by valine (Ala339Val). EMG/NCS confirmed mild asymmetrical sensory-motor axonal neuropathy in lower limbs. Patients' initial non-dermatomal sensory loss fits the textbook description of ‘bathing suit’ pattern associated with acute intermittent porphyria.