Metabolic Acidosis and Hyponatremia in a Patient With Metastatic Melanoma

Abstract

A 72-year-old man with a history of metastatic melanoma and hypertension presented to the hospital with a 2-week duration of weakness and fatigue. He also reported poor appetite and decreased oral intake but no weight loss. He denied shortness of breath, lightheadedness, syncope, nausea, vomiting, or diarrhea. He also denied headache, confusion, polyuria, or polydipsia.Home medications included amlodipine 10 mg once a day, lisinopril 10 mg once a day, and pembrolizumab 200 mg intravenously every 3 weeks. The latter was started 3 months prior to admission and he had recently completed 3 cycles of therapy.On admission, he had blood pressure of 118/78 mm Hg and heart rate of 62 beats per minute. Initial work-up was notable for hyponatremia with serum sodium level of 120 mg/dL and metabolic acidosis with total CO 2 of 16 mmol/L. Other laboratory results are shown in Table 1. A spot urinary protein-creatinine ratio was 0.12 mg/mg, and urine pH was 6.0. Urine analysis did not show any microscopic hematuria or pyuria. There was no glycosuria.Computed tomography scan of the abdomen was normal. Other laboratory studies including titers of serum antinuclear antibody, anti-neutrophil cytoplasmic antibody, and anti-SSA/SSB; tests for hepatitis B and C virus; and levels of C3 and C4 were all unrevealing.

Immune checkpoint inhibitors and kidney disease

“…Distal renal tubular acidosis has been reported in the setting of anti-PD-1 use (pembrolizumab or nivolumab) [60][61][62][63][64]. Herrmann et al [61] described a case series of distal RTA and stained the biopsy specimen for transporters in alpha-intercalated cells, and found decreased expression of vacuolar Hþ-ATPase and anion-exchanger 1.…”