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Kidney Week

Abstract: SA-PO718

Diagnosing Acute Intermittent Porphyria with SIADH

Session Information

Category: Fluid, Electrolytes, and Acid-Base Disorders

  • 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Hsu, Mandy, Penn State College of Medicine, University Park Program, State College, Pennsylvania, United States
  • Majeed, Abdul-Jawad, Penn State College of Medicine, University Park Program, State College, Pennsylvania, United States
  • Roe, Kevin C., Mount Nittany Medical Center, State College, Pennsylvania, United States
Introduction

We present a case of acute intermittent porphyria (AIP) presenting with SIADH. AIP is a rare and often overlooked diagnosis. The case highlights the importance of considering AIP when a patient presents with SIADH. Delay in diagnosis led to delayed treatment, multiple emergency department visits and hospitalizations, and unnecessary testing.

Case Description

A 20-year-old female with a history of anemia and anxiety presented with nausea, vomiting, and abdominal pain. She experienced symptoms for two months and underwent extensive evaluation and prior hospitalization. She described the pain as diffuse, inconsistent, and varying in severity. Prior evaluation included upper endoscopy, colonoscopy, CT scans, X-rays, gynecologic evaluation with pelvic ultrasound, and psychiatric consultation. Laboratory evaluation was consistently notable for hyponatremia with serum sodium ranging from 120-130 mEq/L. Hyponatremia was first attributed to dehydration and anorexia treated with IV fluids, free water restriction and salt tablets. However, when euvolemia was achieved a low serum sodium (129 mmol/L) with inappropriately elevated urine osmolality (331 mOsm/kg) persisted. Once the diagnosis of SIADH was determined, a nephrology consultant recognized the association with AIP. Testing for urine porphobilinogens confirmed the diagnosis. The patient was transferred to a tertiary care center to receive appropriate treatment with hemin infusion. Symptoms improved but evidence of SIADH persisted.

Discussion

Early recognition of AIP is often difficult given the rarity of the disease and because the presentation is variable and nonspecific. Our case demonstrates how the presence of low urine sodium levels may help lead to a diagnosis of AIP. This diagnosis may have been missed had the potential cause of SIADH not been taken into consideration. Prompt diagnosis of AIP is important so hemin therapy can be started early to manage future acute attacks and prevent long-term consequences, such as chronic neuropathic pain. Given that the patient had numerous differential diagnoses, it is important to consider the relationship between SIADH and AIP when presented with repeated unexplained abdominal pain, nausea, and vomiting.

Teaching points:
-Identify the underlying cause when managing SIADH.
-AIP and SIADH have an established relationship. SIADH may result from damage to hypothalamus and hypothalamic-hypophyseal tracts in AIP.