Question

A 40-year-old man with advanced acquired immunodeficiency syndrome presents with an acute chest infection. Investigations confirm a diagnosis of Pneumocystis jirovecii pneumonia. Although he is being treated appropriately, his plasma sodium level is 118 (mEq/L). Results of adrenal function tests are normal.

1. What is the likely cause of his electrolyte disturbance?

2. What the five cardinal features of this condition

Answer 1

1) In patients with acquired immunodeficiency syndrome, the immunity will be low which make them vulnerable to get opportunistic infections like pneumocystis jirovecii pneumonia. .The infection of the pulmonary tract can induce ADH release by the pituitary gland leading to a condition known as syndrome of inappropriate antidiuretic hormone(SIADH). Hyponatremia is one of the common manifestation associated with this condition.Thus,the most likely cause of electrolyte disturbance will be due to SIADH .

2)Five cardinal features of Syndrome of Inappropriate Antidiuretic Hormone.

1. Hypotonic hyponatremia :Due to the increased secretion of antidiuretic hormone,more water is absorbed by the kidneys which causes hyoptonic blood plasma and more sodium is excreted to the urine leads to hyponatremia.
2. Natriuresis : it is the excretion of large amount of sodium in the urine.
3. Urine osmolality in excess of plasma osmolality : the loss of sodium from blood to urine alter the osmolarity of urine and plasma. urine with high sodium level will have increased osmolarity than plasma,where dilution of blood occurs due to water retention and low sodium level.
4. Absence of edema and volume depletion :Even though there is water retention due to continuous ADH release,their will not be any signs of edema because the water is return to circulation causing hemodilution not to the interstitial space.
5. normal renal, thyroid and adrenal function.