Hypodipsia and hypernatremia in congenital hydrocephalus

The PD-1 expression balance between effector and regulatory T cells predicts the clinical efficacy of PD-1 blockade therapies

Immune checkpoint blockade has provided a paradigm shift in cancer therapy, but the success of this approach is very variable; therefore, biomarkers predictive of clinical efficacy are urgently required. Here, we show that the frequency of PD-1⁺CD8⁺ T cells relative to that of PD-1⁺ regulatory T (T_reg) cells in the tumor microenvironment can predict the clinical efficacy of programmed cell death protein 1 (PD-1) blockade therapies and is superior to other predictors, including PD ligand 1 (PD-L1) expression or tumor mutational burden. PD-1 expression by CD8⁺ T cells and T_reg cells negatively impacts effector and immunosuppressive functions, respectively. PD-1 blockade induces both recovery of dysfunctional PD-1⁺CD8⁺ T cells and enhanced PD-1⁺ T_reg cell-mediated immunosuppression. A profound reactivation of effector PD-1⁺CD8⁺ T cells rather than PD-1⁺ T_reg cells by PD-1 blockade is necessary for tumor regression. These findings provide a promising predictive biomarker for PD-1 blockade therapies.

Hypodipsic-hypernatremia syndrome in an adult with polycythemia: a case report

Background

Hypernatremia is a very common electrolyte disorder and is frequently encountered in out-patient as well as in-hospital settings. We describe an adult who was found to have unexplained relative polycythemia and episodic hypernatremia. A diagnosis of idiopathic hypodipsic-hypernatremia syndrome was made and the patient was managed with a water-drinking schedule.

Case presentation

A 24-year-old South African-Indian man was found to have polycythemia in association with episodes of hypernatremia. Investigations indicated that he had relative polycythemia. He experienced no thirst at a time when his serum sodium concentration was found to be 151 mmol/L. Further testing indicated that his renal response to arginine vasopressin was intact and magnetic resonance imaging of his brain revealed no hypothalamic lesions. A diagnosis of idiopathic hypodipsic-hypernatremia syndrome was made and he was managed with a water-drinking schedule that corrected his hypernatremia.

Conclusion

Hypodipsia should always be considered when a patient without physical or cognitive disability presents with unexplained episodic hypernatremia or with relative polycythemia.

Hypodipsia discriminates progressive supranuclear palsy from other parkinsonian syndromes

BACKGROUND

The objective of this study was to evaluate whether the sensation of thirst differs between patients with progressive supranuclear palsy (PSP), multiple system atrophy with predominant parkinsonism (MSA-P), and Parkinson's disease (PD).

METHODS

We administered a standardized thirst questionnaire to age-, sex-, and stage-matched patients with probable PSP, PD, and MSA-P and healthy controls (HC), n = 15/group. In an independent cohort (n = 10/group), we provoked thirst by infusing hypertonic NaCl in age-, sex-, and stage-matched patients with PSP, PD, and MSA-P and recorded plasma osmolality and thirst (visual analog scale).

RESULTS

On questioning, 73% of PSP patients reported a reduced sensation of thirst (hypodipsia) compared with previous years (HC, 0%; PD, 7%; MSA-P, 7%; P < .0001). On NaCl infusion, PSP patients reported significantly lower thirst than did PD and MSA-P patients for all times from 20 to 95 minutes (P < .05). The thirst score at 25 minutes discriminated individual PSP patients well from PD and MSA-P patients.

CONCLUSIONS

Hypodipsia appears helpful in differentiating PSP from PD and MSA-P.