Chronic hyponatremia in a patient with renal salt wasting and without cerebral disease: relationship between RSW, risk of fractures and cognitive impairment

The Natriuretic Peptide System: A Single Entity, Pleiotropic Effects

In the modern scientific landscape, natriuretic peptides are a complex and interesting network of molecules playing pleiotropic effects on many organs and tissues, ensuring the maintenance of homeostasis mainly in the cardiovascular system and regulating the water-salt balance. The characterization of their receptors, the understanding of the molecular mechanisms through which they exert their action, and the discovery of new peptides in the last period have made it possible to increasingly feature the physiological and pathophysiological role of the members of this family, also allowing to hypothesize the possible settings for using these molecules for therapeutic purposes. This literature review traces the history of the discovery and characterization of the key players among the natriuretic peptides, the scientific trials performed to ascertain their physiological role, and the applications of this knowledge in the clinical field, leaving a glimpse of new and exciting possibilities for their use in the treatment of diseases.

Hyponatremia in Patients with Hematologic Diseases

Hyponatremia is the most common electrolyte disorder in clinical practice and is associated with increased morbidity and mortality. It is frequently encountered in hematologic patients with either benign or malignant diseases. Several underlying mechanisms, such as hypovolemia, infections, toxins, renal, endocrine, cardiac, and liver disorders, as well as the use of certain drugs appear to be involved in the development or the persistence of hyponatremia. This review describes the pathophysiology of hyponatremia and discusses thoroughly the contributing factors and mechanisms that may be encountered specifically in patients with hematologic disorders. The involvement of the syndrome of inappropriate antidiuretic hormone (SIADH) secretion and renal salt wasting syndrome (RSWS) in the development of hyponatremia in such patients, as well as their differential diagnosis and management, are also presented. Furthermore, the distinction between true hyponatremia and pseudohyponatremia is explained. Finally, a practical algorithm for the evaluation of hyponatremia in hematologic patients, as well as the principles of hyponatremia management, are included in this review.

Cerebral salt wasting in a patient with myeloproliferative neoplasm

Background

Cerebral salt wasting (CSW) is a rare metabolic disorder with severe hyponatremia and volume depletion usually caused by brain injury like trauma, cerebral lesion, tumor or a cerebral hematoma. The renal function is normal with excretion of very high amounts of sodium in the urine. Diagnosis is made by excluding other reasons for hyponatremia, mainly the syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Case presentation

A 60-year-old patient was admitted to the emergency room with pain in the upper abdomen and visual disturbance two weeks after knee replacement. The patient was confused with severe hematoma at the site of the knee endoprosthesis. Laboratory values showed massive thrombocytosis, leukocytosis, anemia, severe hyponatremia and no evidence of infection. CT scan of the abdomen was inconspicuous. Head MRI showed no ischemia or bleeding, but a mild microangiopathy. A myeloproliferative neoplasm (MPN) was suspected and confirmed by bone marrow biopsy. Cerebral salt wasting syndrome was identified as the cause of severe hyponatremia most likely provoked by cerebral microcirculatory disturbance. The hematoma at the operation site was interpreted as a result of a secondary von Willebrand syndrome (vWS) due to the myeloproliferative neoplasm with massive thrombocytosis. After starting cytoreductive therapy with hydroxycarbamide, thrombocytosis and blood sodium slowly improved along with normalization of his mental condition.

Conclusion

To the best of our knowledge this is the first description of a patient with CSW most likely caused by a microcirculatory disturbance due to a massive thrombocytosis in the context of a myeloproliferative neoplasm.