Rhabdomyolysis presenting with severe hypokalemia in hypertensive patients: a case series
© Wen et al.; licensee BioMed Central Ltd. 2013
Received: 23 July 2012
Accepted: 3 April 2013
Published: 17 April 2013
Rhabdomyolysis presenting with severe hypokalemia as the first manifestation of primary hyperaldosteronism is extremely rare.
Two middle-aged Chinese females were admitted to our emergency department for muscular weakness and limb pain, and both have the history of early onset hypertension. Laboratory test showed elevated creatinine phosphokinase (4, 907 and 8, 531 IU/L) and extremely low serum potassium (1.38 mmol/L and 1.98 mmol/L). Rhabdomyolysis and severe hypokalemia were established as first diagnosis. Hypokalemic rhabdomyolysis was confirmed after nervous system disorders, autoimmune diseases and trauma were excluded. Adrenal computerized tomography scan and postural stimulation test revealed aldosterone-producing adenomas. They both received laparoscopic adrenalectomy and were stable at the 2-year follow-up visit.
The two cases remind physicians to bear in mind the risk of hypokalemia-induced rhabdomyolysis among patients with primary hyperaldosteronism.
Primary hyperaldosteronism (PHA) is a common cause of secondary hypertension. The main clinical manifestations are resistant hypertension and hypokalemia. Hypokalemia induced by PHA is a chronic process and most patients can tolerant the symptoms of malaise, muscular weakness and fatigability. But in some extreme conditions, PHA can induce excessive potassium excretion followed by rhabdomyolysis. Rhabdomyolysis presenting with severe hypokalemia as the first manifestation is rare in primary hyperaldosteronism. We report two cases of PHA diagnosed successfully.
Laboratory data on admission
11.40 × 109/L
8.38 × 109/L
4.71 × 1012/L
4.68 × 1012/L
158 × 109/L
255 × 109/L
Arterial Blood Gas Analysis on Room Air
Based upon these clinical features, we established hypokalemia and rhabdomyolysis as first diagnosis. A series of laboratory examinations were performed for differential diagnosis of rhabdomyolysis. Biopsy results of right biceps brachii muscle revealed degenerated and necrotic muscle fibers with some inflammatory cells infiltrating the perimysium. The electromyogram was normal, which excluded nervous system disorders. Rhabdomyolysis induced by autoimmune diseases were excluded for negative results of autoimmune antibodies.
Hence, we supposed hypokalemia induces rhabdomyolysis. Tests for synchronous serum and urine potassium (First time: serum potassium 3.10 mmol/L, urine potassium 57.98 mmol/24 h; Second time: serum potassium 2.87 mmol/L, urine potassium 48.63 mmol/24 h) illustrated excessive potassium loss. Normal pH in arterial blood eliminated the suspect of renal tubule diseases.
High dose oral potassium supplementation was initiated. Pain and weakness were relieved and serum CPK levels normalized within one week. However, the serum potassium level remained low (3.00 mmol/L) despite potassium supplementation.
Endocrine test results
Basal endocrine data: before postural stimulation test
Endocrine data: 2 hours after postural stimulation test
Rhabdomyolysis is defined as a pathological condition of skeletal muscle cell damage leading to the release of toxic intracellular material into the blood circulation, such as CPK, myoglobin, aspartate aminotransferase, alanine aminotransferase and potassium [1–3]. The syndrome generally presents with the triad muscular pain, weakness and reddish brown urine .
The major causes of rhabdomyolysis include trauma, ischemia, drugs, toxins, metabolic disorders, infections and electrolyte disorders [5, 6]. Especially, severe hypokalemia might play an important role in muscle cell damage [7, 8]. Local potassium levels in capillaries are important regulators for vascular tension. Severe hypokalemia contracted capillaries, reduced muscle blood supply and finally resulting in lysing muscle cells and muscle cell damage [9, 10]. Frank rhabdomyolysis usually occurs only when serum potassium values are below 2.0 mmol/L [8, 11], which possibly induces cardiac arrhythmia and needs emergency treatment.
In PHA, aldosterone excess leads to water-sodium retention and potassium excretion. Patients usually present with hypertension and mild hypokalemia, while malaise and muscular weakness is always tolerable for patients. When vomiting or diarrhea occur or diuretics are used, serum potassium levels might drop to very low levels .
Although rhabdomyolysis usually results in hyperkalemia due to the direct release of intracellular potassium into the extracellular fluid, over-excreted aldosterone in PHA induces potassium excretion into urine. These mechanisms might be the reason we find hypokalemia, instead of hyperkalemia, resulting from rhabdomyolysis in those two cases.
The diagnosis of PHA might be difficult when rhabdomyolysis and severe hypokalemia are the first manifestation. However, when rhabdomyolysis and hypokalemia occur in hypertensive patients, PHA should be considered. Further investigation for PHA should be initiated.
Written informed consent was obtained from the patients for publication of this manuscript and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
ZHANG L and HE W revised the manuscript critically for intellectual content. Most importantly, We would like to thank the patients.
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