RESUMO
Neuromuscular excitability is a vital body function, and Mg2+ is an essential regulatory cation for the function of excitable membranes. Loss of Mg2+ homeostasis disturbs fluxes of other cations across cell membranes, leading to pathophysiological electrogenesis, which can eventually cause vital threat to the patient. Chronic subclinical Mg2+ deficiency is an increasingly prevalent condition in the general population. It is associated with an elevated risk of cardiovascular, respiratory and neurological conditions and an increased mortality. Magnesium favours bronchodilation (by antagonizing Ca2+ channels on airway smooth muscle and inhibiting the release of endogenous bronchoconstrictors). Magnesium exerts antihypertensive effects by reducing peripheral vascular resistance (increasing endothelial NO and PgI2 release and inhibiting Ca2+ influx into vascular smooth muscle). Magnesium deficiency disturbs heart impulse generation and propagation by prolonging cell depolarization (due to Na+/K+ pump and Kir channel dysfunction) and dysregulating cardiac gap junctions, causing arrhythmias, while prolonged diastolic Ca2+ release (through leaky RyRs) disturbs cardiac excitation-contraction coupling, compromising diastolic relaxation and systolic contraction. In the brain, Mg2+ regulates the function of ion channels and neurotransmitters (blocks voltage-gated Ca2+ channel-mediated transmitter release, antagonizes NMDARs, activates GABAARs, suppresses nAChR ion current and modulates gap junction channels) and blocks ACh release at neuromuscular junctions. Magnesium exerts multiple therapeutic neuroactive effects (antiepileptic, antimigraine, analgesic, neuroprotective, antidepressant, anxiolytic, etc.). This review focuses on the effects of Mg2+ on excitable tissues in health and disease. As a natural membrane stabilizer, Mg2+ opposes the development of many conditions of hyperexcitability. Its beneficial recompensation and supplementation help treat hyperexcitability and should therefore be considered wherever needed.
RESUMO
Jevtic D, Djokic D, Redzic D, Aleksic D, Parezanovic M, Pasic S. Secondary hemophagocytic lymphohistiocytosis in a child with Leptospira infection: A case report. Turk J Pediatr 2018; 60: 735-738. Leptospirosis caused by spirochetes of the genus Leptospira in most patients result in very mild illness without jaundice. However, a small portion of patients develop various complications due to the involvement of multiple organ systems. Hemophagocytic lymphohistiocytosis is characterized by prolonged fever, hepatosplenomegaly and cytopenias, hyperferritinemia and hypertriglyceridemias, hyperfibrinogenemia, and hemophagocytosis in bone marrow, lymph nodes, spleen, or liver. Hemophagocytic lymphohistiocytosis associated with leptospirosis is a very rare condition and it should be considered in patients with multiple organ dysfunctions, together with adequate laboratory findings. It can delay the correct diagnosis of leptospirosis and contribute to an adverse outcome. We present a 13-year-old girl with secondary hemophagocytic lymphohistiocytosis caused by leptospira infection and favorable outcome with appropriate antibiotics and corticosteroid therapy.
