Checkpoint Inhibitor Associated Multi-Endocrine Dysfunction Presenting with Euglycemic Ketoacidosis

Immune check point inhibitors have become breakthrough therapy for many types of cancers. They inhibit one of two immune regulatory pathways, the cytotoxic T-lymphocyte antigen 4 (CTLA-4), and ‘programmed death-1’ (PD-1) and (PD-L1) pathways. Removing immune regulation allows for anti-cancer immune responses. They also cause immune related endocrine dysfunction such as hypophysitis, thyroiditis, diabetes mellitus (DM) and primary adrenal insufficiency (AI). We describe a patient on Pembrolizumab (PEM) (an anti-PD-1 inhibitor) who presented with new onset DM, euglycemic diabetic ketoacidosis (DKA) with simultaneous secondary AI.

Case Description :

54-year-old woman with stage 4 non-small cell carcinoma of the lung (NSCLC) with known brain metastasis, was under therapy with carboplastin, paclitaxel and PEM, presented with headache, blurry vision and altered mental status. She had past history of Grave's disease s/p radioactive iodine therapy, currently on levothyroxine. For two weeks, she had decreased oral intake, and generalized weakness. Upon presentation, she was cachectic, BP 152/65, pulse 117 and confabulating. Laboratory evaluation showed: serum glucose 72 mg/dL, Na 139 mmol/L , K 3.2 mmol/L, Cl 113 mmol/L, HCO3 11 mmol/L,  anion gap 15 mmol/L, beta-hydroxybutyrate 4.8 mmol/L, lactic acid 0.7 mmol/L, venous pH 7.2 and base excess -16.6 mmol/L. The delta-delta gap was 10 mmol/L, compatible with a mixed anion-gap and hyperchloremic acidosis (HCA). Antibodies to GAD-65, and Zinc transporter-8 were negative. To evaluate euglycemia despite DKA, levels were obtained for serum cortisol 1 mcg/dL, and ACTH < 1 pg/mL confirming secondary AI. MRI neuroimaging showed several metastatic brain lesions, a small pituitary gland without stalk enhancement or thickening. Management of euglycemic ketoacidosis required high dose glucose infusion ( >10 g/hour), stress doses of hydrocortisone (HC), and infusion of low chloride solute for HCA.

Discussion :

Awareness of the potential multi-endocrine dysfunction, directed us towards the urgent institution of therapy for DKA with supplementation of stress dose HC for presumed AI, the latter as a cause of relative “hypoglycemia”. Central AI was confirmed with undetectable levels of cortisol and ACTH. Although less frequent than with CTLA-4 inhibitors, PD-1 inhibitors are associated with hypophysitis even without abnormalities on pituitary MRI. The DM (associated with PD-1 inhibitors) although autoimmune is nature, is “antibody” positive approximately 50% of the time. Further therapy for both euglycemic DKA and HCA required adjustment of the conventional management for DKA.