A 26-year-old woman is evaluated in the ER for diffuse abdominal pain and nausea. The pain started 1 day ago and is currently at its maximum intensity. She denies fever but has noticed constipation and dark urine. She had similar episodes in the past and underwent appendectomy and cholecystectomy on two different occasions. On physical examination, she is tachycardic with diffuse abdominal tenderness but no rebound tenderness. Her bowel sounds are slightly sluggish. On neurological examination, she has decreased sensation to fine and crude touch in both lower extremities up to her knees. Her hemoglobin, WBC, and platelet count are normal. She has mild transaminitis with alanine transaminase (ALT) 123 IU/L, aspartate transaminase (AST) 160 IU/L, and alkaline phosphatase (ALP) 122 IU/L. Urine is red but urine dipstick is negative for blood, leukocyte esterase, nitrite, glucose, or protein. Urine porphobilinogen and total porphyrin level are elevated, plasma porphyrin level is normal. What is the most likely explanation of her recurrent symptoms?