Calcineurin inhibitor-related hyperkalemia is caused by hyporeninemic hypoaldosteronism and fludrocortisone is an effective treatment: Report of a case series and review of the literature.

INTRODUCTION: Calcineurin inhibitors (CNIs) are widely used in transplantation. Although CNI-related hyperkalemia is common (10%-60.6%), the underlying pathogenetic mechanism is not well-elucidated and may lead to dose adjustment or treatment withdrawal. OBJECTIVE: The aim of this study is to describe CNI-related hyperkalemia due to hyporeninemic hypoaldosteronism in pediatric transplant recipients who were successfully treated with fludrocortisone. METHOD: In a total of 55 hematopoietic stem cell (HSCT) and 35 kidney transplant recipients followed according to institutional immunosuppression protocols, recipients diagnosed with CNI-related hyperkalemia were reviewed. Recipients who were receiving intravenous fluid, potassium, or were diagnosed with hemolysis, acute graft rejection, or had an eGFR < 30 mL/min/1.73m2, were excluded. A detailed analysis of clinical history as well as biochemical studies was carried out to reveal possible pathophysiology. RESULTS: Three pediatric transplant recipients (one HSCT, two kidney transplantation) with findings of hyperkalemia, hyponatremia, and a mild elevation in blood urea nitrogen while on CNIs were recruited. Urinary potassium excretion was diminished while sodium excretion was increased. Plasma aldosterone levels were low, and renin was not increased in response. Primary adrenal insufficiency was ruled out, and hyporeninemic hypoaldosteronism was diagnosed. CNI-related hyperkalemia was detected earlier in case 1, who had HSCT (22 days), than in the second and third cases, who had kidney transplantation (24 and 30 months post-transplantation, respectively). The discrepancy was hypothesized to be explained by higher overall CNI dose due to higher serum target CNI used in HSCT than kidney transplantation. Electrolyte imbalance was reversed upon administration of physiologic dose fludrocortisone (0.05 mg, daily), while fludrocortisone was ceased after CNI withdrawal in case 1, which is additional evidence for the etiological association of CNIs and hyporeninemic hypoaldosteronism. CONCLUSION: Our three cases strengthen the premise that CNI-related hyperkalemia may be due to hyporeninemic hypoaldosteronism, and the timing and severity may be related to CNI dose. Fludrocortisone is a safe and effective treatment in CNI-related hyperkalemia, providing maintenance of CNIs, which are one of the essential therapeutic agents for pediatric transplantation.

ER ribosomal-binding protein 1 regulates blood pressure and potassium homeostasis by modulating intracellular renin trafficking.

BACKGROUND: Genome-wide association studies (GWASs) have linked RRBP1 (ribosomal-binding protein 1) genetic variants to atherosclerotic cardiovascular diseases and serum lipoprotein levels. However, how RRBP1 regulates blood pressure is unknown. METHODS: To identify genetic variants associated with blood pressure, we performed a genome-wide linkage analysis with regional fine mapping in the Stanford Asia-Pacific Program for Hypertension and Insulin Resistance (SAPPHIRe) cohort. We further investigated the role of the RRBP1 gene using a transgenic mouse model and a human cell model. RESULTS: In the SAPPHIRe cohort, we discovered that genetic variants of the RRBP1 gene were associated with blood pressure variation, which was confirmed by other GWASs for blood pressure. Rrbp1- knockout (KO) mice had lower blood pressure and were more likely to die suddenly from severe hyperkalemia caused by phenotypically hyporeninemic hypoaldosteronism than wild-type controls. The survival of Rrbp1-KO mice significantly decreased under high potassium intake due to lethal hyperkalemia-induced arrhythmia and persistent hypoaldosteronism, which could be rescued by fludrocortisone. An immunohistochemical study revealed renin accumulation in the juxtaglomerular cells of Rrbp1-KO mice. In the RRBP1-knockdown Calu-6 cells, a human renin-producing cell line, transmission electron and confocal microscopy revealed that renin was primarily retained in the endoplasmic reticulum and was unable to efficiently target the Golgi apparatus for secretion. CONCLUSIONS: RRBP1 deficiency in mice caused hyporeninemic hypoaldosteronism, resulting in lower blood pressure, severe hyperkalemia, and sudden cardiac death. In juxtaglomerular cells, deficiency of RRBP1 reduced renin intracellular trafficking from ER to Golgi apparatus. RRBP1 is a brand-new regulator of blood pressure and potassium homeostasis discovered in this study.

Acid-Base Imbalance in Pseudohypoaldosteronism Type 1 in Comparison With Type IV Renal Tubular Acidosis.

Context: Pseudohypoaldosteronism type 1 (PHA1) has been treated as a genetic variant of type IV renal tubular acidosis (RTA), leading to the conception that PHA1 develops hyperchloremic acidosis with a normal anion gap (AG). Objective: To delineate the acid-base imbalance in PHA1A (dominant type) and PHA1B (recessive type). Methods: We conducted the following: (1) a retrospective chart review of our patient with PHA1B, and (2) a literature search of PHA1 cases focusing on acid-base balance. The main outcome measures were the incidence and nature of acidosis, including chloride levels and AG. Results: In our patient with PHA1B, 7 salt-wasting episodes were analyzed. Acidosis was ascertained each time, and it was accompanied by hypochloremia except in 1 episode. AG was elevated in 5 episodes, while hyperlacticaemia was present in 3. In the literature, 41 cases of PHA1A and 65 cases of PHA1B have been identified. During salt-wasting crises, acidosis developed in 85% of PHA1A cases and 87% of PHA1B cases. Hypochloremia was present in 69% of PHA1A cases with available data (n = 13) and 54% of eligible PHA1B cases (n = 13), with mean chloride levels of 96 mEq/L and 95 mEq/L, respectively. Increased AG was less frequently reported (14% in PHA1A and 44% in PHA1B). Conclusions: Patients with PHA1 frequently presented with metabolic acidosis. However, hyperchloremia may not be a universal finding, whereas hypochloremia and increased AG may occur in a substantial proportion of the patients.

Persistent severe hyperkalemia following surgical treatment of aldosterone-producing adenoma.

Primary aldosteronism is one of the most common causes of secondary hypertension. This condition is characterized by autonomous hypersecretion of aldosterone which produces sodium retention and potassium excretion, resulting in high blood pressure and potential hypokalemia. Transient postoperative hyporeninemic hypoaldosteronism with an increased risk of hyperkalemia may occur in some patients. We report the case of a 63-year-old patient with persistent hypokalemia, periodic paralysis, and refractory hypertension who was diagnosed with primary hyperaldosteronism due to elevated aldosterone, undetectable plasmatic renin concentration, and the presence of a left adrenal mass. One month after the surgery, the patient was admitted with signs of severe hyperkalemia (8 mmol/L) and worsened renal function, thus requiring hemodialysis. Fluid resuscitation, loop diuretic, and sodium bicarbonate treatment decreased his potassium. Zona glomerulosa insufficiency was confirmed by hormonal tests which exposed low aldosterone-renin axis. The fludrocortisone treatment was initiated and maintained, with consequent potassium and creatinine stabilization. Old age, long duration of hypertension, impaired renal function, severe hypokalemia before surgery, and large size of the aldosterone-producing adenoma are important risk factors for serious potassium imbalance after removal of the adenoma. We have to consider monitoring the patients after surgery for primary hyperaldosteronism in order to prevent severe hyperkalemia; therefore, postoperative immediate follow-up (arterial pressure, potassium, and renal function) is mandatory.

Clinical Observation on Hyperkalemic Distal Renal Tubular Acidosis / 대한신장학회잡지

PURPOSE: Renal tubular aicdosis (RTA) is a disorder of renal acidification out of porportion to the reduction in glomerular filtration rate. Type IV RTA refers to hyperkalemic metabolic acidosis resulting from aldosterone deficiency or resistance. The incidence of each type RTA has not been reported exactly, however reports on type IV RTA have been recently increasing. METHODS: A retrospective clinical analysis was performed in 50 patients with hyperkalemic distal renal tubular acidosis diagnosed between Jan. 1984 and Feb. 2003 at Department of Internal Medicine, Keimyung University, Dongsan Medical Center. RESULTS: From 1984 to 2003, 50 cases of hyperkalemic distal renal tubular acidosis were diagnosed. The mean age was 50.8+/-19.5 years. The two most common conditions were posttransplantation (28%), and diabetes mellitus (22%), which were followed by hypertension (12%), systemic lupus erythematosus (12%), chronic renal failure (12%), and others (26%). Asymptomatic hyperkalemia (34%), and muscle weakness (28%) were the two most common clinical presentations. All patients demonstrated normal anion gap acidosis with positive urine anion gap. The mean creatinine clearance was 25.6+/-16.4 mL/min. The mean baseline PRA and aldosterone levels were 3.82+/-7.16 ng/mL/hr and 110.02+/-108.2 ng/mL, respectively. Hyperkalemia was well responded to 9-alpha-fludrocortisone, furosemide, K-exchane resin, and combinations of these regimens. CONCIUSION: Type IV RTA is the most common type of RTA in children and adults, and can be an important cause of asymptomatic hyperkalemia. Therefore, type IV RTA should be included in the diffrential diagnosis of unexplained hyperkalemia in various clinical settings.

Chronic hyponatremia of Sheehan's syndrome / 대한내과학회지

Sheehan's syndrome has been attributed to ischemic damage of the pituitary gland or hypothalamic-pituitary stalk during the peripartum period. Well-described clinical features of Sheehan`s syndrome include hypothyroidism, growth hormone deficiency, hypogonadism, hypoprolactinemia, adrenal insufficiency, and different sodium and water disturbance. The occurrence of sodium and water disturbances associated with Sheehan`s syndrome depends on the degree of pituitary damage, time of onset since the initial pituitary insult, and concurrent medical conditions that also may play a role in sodium and water balance. Chronic hyponatremia is the most common presentation of altered sodium levels in patients with Sheehan`s syndrome. The chronic nature of the presenting hyponatremia suggests more subtle changes of panhypopituitarism or better adaptive mechanism. Although controversial, another mechanism proposed for hyponatremia in the chronic setting involves alternation in the renin-angiotensin/aldosterone system with resulting sodium wasting. We presented a patient with Sheehan`s syndrome associated with hyporeninemic hypoaldosteronism and hyponatremia 53 years old women, who had 4th baby delivery with severe blood loss about 25 years ago, was admitted to hospital because of general weakness. The patient was diagnosis Sheehan`s syndrome with hyponatremia. In addition, we performed hormonal study to find cause of hyponatremia. The results were hypopituitarism and hyporeninemic hypoaldosteronism. Hyponatremia was corrected by hormonal therapy (glucocorticoid,synthyroid,estrogen). The patient felt well-being sensation and was followed up the out-patient department.

A Case of Liddle's Syndrome Associated with Muscle Weakness / 대한신장학회잡지

Liddle's syndrome was described in 1963 by Liddle, et al., as the disease featuring a hypertension and hypokalemia but with negligible secretion of aldosterone. This syndrome, which morphologically belongs to an abnormal intrinsic tubular disorder with normal renal function, is characterized by hypokalemia, metabolic alkalosis, and hypertension due to the abnormal increase in excretion of potassium in distal tubules or collecting duct and the increase in reabsorption of sodium in distal tubules. This syndrome, which is rare disease, is observed with the low level of plasma and urinary aldosterone and suppressed plasma renin level and is known as dominant mode of inheritance with a family background. The authors paid attention to a 79-year-old man who showed a high blood pressure of 210/130mmHg as well as musle weakness, especially lower extremities due to metabolic alkalosis featuring a hypokalemia level of 2.0mEq/L when he was admitted to our hospital, Because his serum potassium were not improved with the medication of intravenous potassium supply, and his blood pressure continued to be high without the improvement of muscle weakness, we prescribed 300mg of spironolactone for two weeks. His symptom, however, was not cured. Then, instead of spironolactone, we prescribed 150mg of triamterene and a low salt diet which finally improved his symptoms. Because there has been no reported case in the Korean medical literature, we report a case of successfully treated Liddle's syndrome due to triamterene administration.

Hyperkalemia due to hyporeninemic hypoaldosteronism with liver cirrhosis and hypertension

A 49-year-old man with liver cirrhosis and hypertension was found to have hyperkalemia out of a degree of renal insufficiency and metabolic acidosis with low to normal anion gap, aggravated by volume contraction with diarrhea and medications (captopril, spironolactone and atenolol) interfering with potassium homeostasis. Plasma renin activity and serum aldosterone levels of this patient on a regular diet after discontinuation of medications were very low compared to those of five other cirrhotic patients with normokalemia as controls. Also, the renin-aldosterone stimulation testing on this patient performed by sodium restricted diet and furosemide, upright position and by angiotensin converting enzyme inhibition (captopril, 50 mg) showed the blunted renin and aldosterone responses to each of these stimuli, almost no changes from baseline renin and aldosterone levels, it was concluded that the underlying defect responsible for hyperkalemia in this case was hyporeninemic hypoaldosteronism and this was aggravated by other factors or drugs affecting potassium homeostasis.