Case Presentation: A 22-year-old healthy female presented in April 2021 for abdominal pain during menstruation. Vital signs and workup with blood counts, metabolic, pregnancy, and sexually transmitted infection panels were unremarkable. Urinalysis showed nitrites, pyuria, bilirubin, and urobilinogen. Ultrasound and CT of the abdomen/pelvis were unremarkable. She was diagnosed with cystitis and prescribed cefuroxime. Urine culture resulted negative.In May she contracted mild COVID-19 and recovered. Two weeks later, she received her first dose of the BNT162b2 (Pfizer) COVID-19 vaccine. One week later, she was prescribed propranolol for palpitations and tachycardia. In June, she developed upper extremity hyporeflexia and proximal weakness. Laboratory and imaging results are summarized in Table 1. Her preliminary diagnosis was cervical variant Guillain-Barré syndrome (GBS) due to COVID-19 infection or vaccination. She received intravenous immunoglobulin and prednisone, and was discharged to rehabilitation.In October, she presented with abdominal pain and received trimethoprim-sulfamethoxazole for presumed cystitis. Three days later, she developed palpitations, chest pain, upper extremity weakness and areflexia. EKG showed sinus tachycardia. Labs showed mild hyponatremia and transaminemia; cardiac enzymes were negative. A urine porphobilinogen screen was positive. Reduced RBC porphobilinogen deaminase and markedly elevated quantitative urine porphyrins confirmed the diagnosis of acute intermittent porphyria (AIP). She received hemin for 4 days with clinical improvement.

Discussion: AIP is an autosomal dominant disease caused by deficiency of porphobilinogen deaminase, an enzyme in hepatic heme synthesis. AIP is summarized in Table 2. AIP should be considered in reproductive-aged females presenting with abdominal pain and variable constitutional, autonomic, neurologic, or psychiatric symptoms, especially in association with triggers of medications, alcohol, tobacco, menses or stress. Diagnosis is made via urine porphobilinogen screen and confirmed by quantitation during an acute flare. Most urine porphyrin screens do not measure porphobilinogen and can miss the diagnosis. Diagnosis is often delayed for years. Acute attacks can be life-threatening and patients often undergo unnecessary abdominal surgeries prior to correct diagnosis.GBS is commonly misdiagnosed in patients with AIP. COVID-19 infection, and to a lesser extent, adenovirus-vector COVID-19 vaccines, are implicated in developing GBS. The mRNA vaccines do not appear to increase the risk of GBS.AIP motor symptoms improve, often resolving within a year. Prognosis of AIP is good with diagnosis and treatment with hemin. Givosiran is an FDA approved therapeutic given via monthly injection to reduce recurrent attacks. Patients with recurrent attacks despite treatment may require liver transplant.

Conclusions: In this case, a young adult female developed episodic abdominal pain followed by acute motor neurologic dysfunction and tachycardia. Several clues in this case suggested acute intermittent porphyria: episodic abdominal pain without pathologic findings in a young adult female, concurrent neurologic (especially motor) symptoms and temporal associations with menses and trigger medications. While GBS was suspected, her symptoms started before COVID-19 infection and vaccine. Availability bias may have delayed diagnosis due to COVID-19 being at the forefront of medical literature and media reporting.

IMAGE 1: Table 1: June 2021 Diagnostic Testing Results

IMAGE 2: Table 2: Epidemiology, Clinical Manifestations, Diagnosis, and Treatment of Acute Intermittent Porphyria