Porphyrias, particularly acute intermittent porphyria (AIP), are rare, inherited disorders of heme synthesis. On the other hand, systemic lupus erythematosus (SLE) is an uncommon autoimmune disease that affects women predominantly. The coexistence of AIP and SLE is rare. We report a case of concomitant diagnosis of AIP and SLE in a 21-year-old woman who presented with recurrent acute abdominal, chest, and back pain associated with nausea and vomiting, followed by arthralgia, multiple joint pain, and rash. Investigations revealed severe hyponatremia related to SIADH (syndrome of inappropriate antidiuretic hormone secretion) with a positive SLE antibody panel and a positive urine screen for porphobilinogen. Molecular test confirmed the diagnosis of AIP with a pathogenic mutation in the HMBS gene.