Rhabdomyolysis: A rare presentation of aldosterone-producing adenoma
A 42-year-old woman presented with acute onset lower limb paralysis associated with severe proximal muscle pain. These symptoms were not associated with respiratory difficulty, dysphagia, dysarthria or sensory symptoms and there was no associated backache, fever, rash or constitutional symptoms. She had a 2 year history of hypertension, which was poorly controlled despite treatment with a combination of nifedipine, atenolol and losartan. She was treated by a general practitioner and at initial diagnosis of hypertension had undergone biochemical evaluation including serum electrolyes, which had been within normal limits. She experienced two similar, but short lasting episodes of weakness in the preceding year, but had not been investigated. Three days prior to admission she had been given Frusemide as add on therapy by her general practitioner due to uncontrolled hypertension. Her blood pressure on admission was 160/100 mmHg. Clinical examination favored an acute onset myopathy with symmetric flaccid paralysis of lower limbs (muscle power - 3/5) with normal muscle power (5/5) in the upper limbs.\nInitial work-up revealed severe hypokalemia (potassium - 2.0 mmol/l) with an elevated creatine kinase (CK) of 11347 IU (16-190) and increased lactic dehydrogenase of 856 IU/l (240-480). Patient's urine was positive for myoglobin with a high urinary myoglobin 4,170 μg/l. Serum creatinine was 130 μmol/l. In addition, patient had high urinary potassium of 19.45 mmol/24 h with metabolic alkalosis (pH - 7.540, HCO3-38 mmol/l, base excess - 15 mmol/l and PCO2-44 mmHg).\nThe other biochemical values on initial evaluation were as follows; serum aspartate aminotransferase - 244 IU/l (up to 35 IU/l); alanine aminotransferase - 193 IU/l (2-40); Sodium - 145 mmol/l; blood urea - 45 mg/dl; calcium - 0.9 mmol/l (1.12-1-32); phosphorus - 2.7 mg/dl (2.7-4.5); magnesium - 1.4 mg/dl (1.58-2.55); fasting blood glucose 110 mg/dl and the total protein was 7.6 g/dl with albumin 3.2 g/dl. Thyroid function tests were normal with a free T4 level of 1.02 ng/dl and thyroid-stimulating hormone 3.2 μIU/ml.\nBased on the above findings, patient was diagnosed as having hypokalemic paralysis and rhabdomyolysis. Treatment was initiated by oral and intravenous supplementation of potassium and after 10 days, muscular strength and CK levels had returned to normal. Conduction studies and electromyography, which were performed after the correction of hypokalemia, were normal.\nThe coexistence of hypertension, hypokalemia with high urinary potassium loss in association with metabolic alkalosis raised the possibility of primary aldosteronism (PA), which lead to further hormonal evaluation. Aldosterone levels were 22,600 ng/dl (normal, 3.6-24.0 ng/dl) and the plasma renin activity (PRA) value was below the detection limit of our method (0.2 ng/ml/h). Aldosterone/renin ratio (ARR) was 113,000 ng/ml per ng/ml/h (<10). Abdominal ultrasound did not reveal adrenal lesions, but abdominal computed tomography scan showed a 20 mm × 16 mm hypodense mass in the medial limb of the right suprarenal gland []. She underwent right sided adrenalectomy and pathological examination of the gland confirmed a 20 mm adrenal adenoma. Post-operatively the patient was normokalemic without spiranolactone and the PRA was 0.52 ng/ml/h; aldosterone was 1.3 ng/dl with a reduced ARR of 2.5 (<20) ng/ml per ng/ml/h. After 4 weeks of discharge, her BP was normal without any antihypertensives and she was normokalemic with normal muscle strength.