Introduction
Hyperammonemia, a condition characterized by elevated levels of ammonia in the blood, can lead to encephalopathy and is primarily caused by liver diseases and urea cycle disorders. Ornithine transcarbamylase deficiency (OTCD) is a genetic disorder that impairs the urea cycle, leading to hyperammonemia. This article discusses a case of hyperammonemic encephalopathy triggered by a high-dose dexamethasone suppression test in a woman with OTCD.
Case Report
A 46-year-old woman with a 1.3-cm right adrenal incidentaloma causing mild autonomous cortisol secretion underwent a high-dose dexamethasone suppression test to confirm adrenocorticotropic hormone (ACTH) independency. The next day, she presented to the emergency room with confusion and somnolence, scoring 10 on the Glasgow Coma Scale. Initial laboratory results showed elevated ammonia levels (289.51 mg/dL), with normal alanine transaminase, creatinine, and blood urea nitrogen levels.
Further investigation revealed that the patient was an OTCD carrier, a condition that had previously caused the neonatal deaths of her brother and son. Treatment included L-arginine, L-carnitine, rifaximin, and continuous renal replacement therapy. After three days, her serum ammonia level decreased to 78.34 mg/dL, and her Glasgow Coma Scale score improved to 15.
Discussion
OTCD is an X-linked urea cycle disorder that affects men more severely due to their single X chromosome. Women with OTCD typically do not develop severe symptoms until later in life, if at all. Glucocorticoids, such as dexamethasone, can exacerbate OTCD by increasing protein substrates that are converted to ammonia.
Clinical Implications
This case highlights the importance of a thorough medical history when administering glucocorticoids. Although the high-dose dexamethasone suppression test is generally safe, it can trigger severe hyperammonemia in OTCD carriers. Clinicians should consider OTCD in the differential diagnosis for adult-onset hyperammonemic encephalopathy.
Treatment and Management
In cases of hyperammonemia, treatment includes ammonia-lowering agents such as L-arginine, L-carnitine, and rifaximin, along with continuous renal replacement therapy. Sodium benzoate and sodium phenylbutyrate can also be used to remove nitrogenous waste from the blood. Patients with urea cycle disorders should maintain a lifelong low-protein diet to manage their condition.
In this case, the patient’s cortisol levels after high-dose dexamethasone administration confirmed ACTH independency and adrenal adenoma as the cause of cortisol excess. However, due to the risk of hyperammonemic encephalopathy, the patient opted for follow-up without surgery.
Conclusion
This case underscores the critical need for a comprehensive medical history when administering high doses of glucocorticoids. Clinicians should be aware of the potential for rare side effects, such as hyperammonemic encephalopathy, in patients with urea cycle disorders like OTCD.
References
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