A 28-year-old woman comes to the emergency department due to bilateral upper extremity weakness and abdominal pain. The patient has had progressive weakness of the upper extremities for 2 days and severe, diffuse, poorly localized abdominal pain for 1 day. Temperature is 37.3 C (99.1 F), blood pressure is 148/86 mm Hg, and pulse is 112/min. On physical examination, the patient appears restless and is diaphoretic. There is no scleral icterus. The abdomen is soft and nontender, with no organomegaly, guarding, or rebound tenderness. Bowel sounds are decreased. Neurological examination shows normal cranial nerves, weakness of the proximal upper extremity muscles, and loss of the biceps and triceps reflexes on both sides. Laboratory results are as follows: Which of the following is most likely to yield the diagnosis in this patient?

Question

A 28-year-old woman comes to the emergency department due to bilateral upper extremity weakness and abdominal pain.  The patient has had progressive weakness of the upper extremities for 2 days and severe, diffuse, poorly localized abdominal pain for 1 day.  Temperature is 37.3 C (99.1 F), blood pressure is 148/86 mm Hg, and pulse is 112/min.  On physical examination, the patient appears restless and is diaphoretic.  There is no scleral icterus.  The abdomen is soft and nontender, with no organomegaly, guarding, or rebound tenderness.  Bowel sounds are decreased.  Neurological examination shows normal cranial nerves, weakness of the proximal upper extremity muscles, and loss of the biceps and triceps reflexes on both sides.  Laboratory results are as follows:  Which of the following is most likely to yield the diagnosis in this patient?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d54e_2d76_bc81_952a6bb93946_MD0003_00 This patient with diffuse abdominal pain, peripheral neuropathy (eg, upper extremity weakness, areflexia), and positive urobilinogen most likely has acute intermittent porphyria (AIP). AIP is an autosomal dominant disorder of the heme synthesis pathway that results in reduced activity of porphobilinogen deaminase, leading to buildup of neurotoxic heme pathway intermediates (ie, porphobilinogen, aminolevulinic acid). heme synthesis pathway Patients typically experience discrete attacks after exposure to certain triggers, including medications (eg, progesterone-containing drugs), tobacco, alcohol, and physiologic stressors (eg, surgery, fasting); however, the trigger may not always be identified. Manifestations are related to neurotoxicity in various organ systems and include: Abdominal pain: Because the pain is neuropathic, it can be diffuse, although tenderness, rebound, and guarding are absent. Nausea/vomiting, hypoactive bowel sounds, and constipation may occur. Peripheral neuropathy: Most prominent in the proximal upper extremities Autonomic dysfunction (eg, tachycardia, diaphoresis, tremor) Neuropsychiatric manifestations (eg, restlessness, hallucinations) Unlike other porphyrias (eg, porphyria cutanea tarda), photosensitive cutaneous findings are absent. Hyponatremia may occur due to syndrome of inappropriate antidiuretic hormone. Urinary porphyrins and porphobilinogen results in red-tinged urine (ie, positive for urobilinogen, negative for blood) that darkens when exposed to air and light. Elevated urinary porphyrin levels confirm the diagnosis. when exposed to air and light (Choice A) Lead poisoning also results in abdominal pain and neuropsychiatric manifestations; however, patients typically have fatigue, joint pain, and anemia. Hyponatremia and dysautonomia is unexpected. (Choice B) On cerebrospinal fluid (CSF) analysis, albuminocytologic dissociation (elevated CSF protein with normal CSF leukocyte count) is classically seen in Guillain-Barré syndrome, which typically occurs after a gastrointestinal illness and presents with ascending weakness. Elevated urobilinogen is unexpected. (Choice C) JAK2 mutations are common in myeloproliferative disease (eg, polycythemia vera), which can cause portal vein thrombosis that leads to abdominal pain and may occasionally be associated with sensorineural neuropathy. However, blood cell counts would be abnormal (eg, elevated hemoglobin). (Choice D) Mesenteric angiography can be used to diagnose polyarteritis nodosa, which also causes abdominal pain and mononeuritis multiplex; however, renal failure, skin manifestations (eg, tender nodules), and constitutional symptoms (eg, fever, fatigue) are typical. (Choice E) Serum ceruloplasmin is often low in Wilson disease, which can cause neuropsychiatric symptoms and abdominal pain related to hepatitis. However, patients typically have elevated liver function studies, hepatomegaly, and Kayser-Fleischer rings on examination. Educational objective: Acute intermittent porphyria is a disorder of the heme synthesis pathway that results in reduced activity of porphobilinogen deaminase. Patients experience discrete attacks of abdominal pain, peripheral neuropathy with proximal muscle weakness, autonomic dysfunction, and neuropsychiatric manifestations. Urobilinogen levels are typically elevated, and elevated urinary porphyrin levels confirm the diagnosis.

A 28-Year-Old Woman Comes to the Emergency Department Due to Bilateral