Symptoms initially pointed to toxic alcohol ingestion.
The individual had a history of alcohol abuse and a previous suicide attempt. He initially presented with altered mentation accompanied by an anion gap metabolic acidosis with an elevated osmolar gap, authors wrote.
As the patient’s ultimate diagnosis was multiple myeloma, the case “demonstrates the multiple factors that can impact both the anion and osmolar gaps” and “shows that the traditionally held dogma about the meaning of anion or osmolar gaps may cloud an otherwise more obscure etiology,” they explained.
The case also underscores how essential it is to recognize multiple myeloma early, so providers can initiate appropriate chemotherapy and increase the odds of preserving renal function.
Multiple myeloma can present in many ways, including acute kidney failure and an altered mental status. However, when renal failure is accompanied by altered mentation, it can be difficult to determine the etiology and guide treatment, the researchers said. Even when reliable first-hand collateral information is available, etiology can be elusive, they added.
The patient in the current case study was a 62-year-old man who presented to the emergency department with an altered mental status, hypothermia, and mild hypertension. The patient’s labs revealed a serum bicarbonate of 6 mmol/L, lactate of 5 mmol/L, and an anion gap of 26. He had been taking lithium for bipolar disorder.
His osmolar gap was elevated to 42 mOsm/L (normal <10 mOsm/L). Given his history of alcoholism and a previous suicide attempt, this “raised concerns for acute kidney failure secondary to toxic ingestion,” authors wrote.
The patient began emergent hemodialysis (HD), was treated with fomepizole, and was admitted to the medical intensive care unit; after 3 sessions of daily HD, his encephalopathy and acidemia improved. His osmolar gap also closed after the third HD session.
Once the patient became lucid, he said he had self-discontinued his lithium and other psychiatric medications weeks earlier, but denied suicidal ideation, including toxic ingestion, the authors said.
After doctors ruled out other explanations for his lack of renal recovery, they performed more labs and a renal biopsy.
“Bone marrow biopsy confirmed plasma cell myeloma with t(11;14) translocation and the patient was started on chemotherapy with cyclophosphamide, bortezomib, and dexamethasone to attempt to salvage his renal function,” authors wrote.
Throughout the patient’s admission, renal function did not improve and the patient remained in the hospital until outpatient dialysis was arranged.
Continued issues with depression led the patient to stop attending follow-up appointments and dialysis sessions, and he returned a few months later with a similar presentation.
The researchers suspect the patient’s anion gap metabolic acidosis was influenced by his uremia, elevated lactate, gammopathy, and elevated beta-hydroxybutyrate.
Overall, “this case demonstrates how the osmolar gap can be a beneficial screening tool for toxic ingestion; however, its sensitivity and specificity are limited by a wide range of normal values and the multiple factors that can contribute to its elevation. As such, it must be interpreted with caution,” they said.
Although anion gap metabolic acidosis can be present secondary to kidney failure, a significant increase in the osmolar gap is not common, they added, making the current case an “unusually striking example.”
“This case highlights that acute myeloma can present in a dramatic fashion, especially in a healthy individual with a high tolerance for the sequelae of progressive renal failure,” the researchers concluded.
Burkholder NJ, Sweet LM, and Kelly EL. From toxic ingestion to cancer: dramatic acidosis as a myeloma-defining event. Cureus. Published online May 4, 2023. doi:10.7759/cureus.38542