[A case of Gitelman's syndrome presenting with severe hypocalcaemia and hypokalemic periodic paralysis]

A 63-year-old woman was admitted with fatigue, general malaise, paraesthesiae, muscle cramping and weakness of the limbs. Since the age of 13, she had suffered from a transient lower extremities paralysis 3 times. Past history was unremarkable. There was no family history of disease. In addition, she denied any form of self-medication, surreptitious diuretic and laxative abuse, persistent vomiting and diarrhea. The blood pressure was 120/70 mmHg, BMI = 23.0 kg/m2, WHR = 0.84. A little anxious. The results of physical examinations were unnoticeable. The cranial-nerve functions were intact. Manual muscle tests revealed her extremities in normal condition. Sensation was normal in all modalities. The deep tendon reflexes were present but decreased mildly.

Laboratory tests showed moderate to severe hypokalemia with a serum potassium concentration of 2.77 to 3.17 mmol/L, hypomagnesemia (0.31-0.35 mmol/L), hypocalcaemia (1.79-1.99 mmol/L), hypocalciuria (0.12-1.10 mmol/24 h), and metabolic alkalosis. The patient had elevated plasma renin activity and normoaldosteronism; her parathyroid hormone level was normal. Urinary calcium to creatinine ratio was (5.17-23.57) x 10(-3) mg/mg Cr. The renal clearance studies in this patient using furosemide or hydrochlorothiazide disclosed that urine volume and chloride clearance (CCL) were increased after furosemide administration, but there was no obvious change after the administration of hydrochlorothiazide. Furthermore, the distal fractional chloride reabsorption [CH2O/(CH2O+CCI)] was dramatically decreased by furosemide administration, whereas thiazide had little effect on it. These findings pointed to the presence of a non-functional thiazide-sensitive sodium/chloride cotransporter in the distal convoluted tubule, so the diagnosis of Gitelman's syndrome (GS) was made.

The patient was treated with indomethacin 50 mg, tid; after 3 days, the potassium increased, but calcium and magnesium serum levels failed to improve. So triamterene 50 mg, tid was also administrated. After 4 days, the serum levels of potassium, calcium were normalized, and the serum levels of magnesium increased from 0.35 mmol/L to 0.52 mmol/L; weakness and fatigue improved markedly, the clinical symptoms disappeared. The 18-month-follow-up study found the magnesium serum level normal.

GS may be present with severe hypocalcaemia and hypokalemic periodic paralysis; the renal clearance studies by diuretic administration may be of help in diagnosing Gitelman's syndrome, and the combined use of indomethacin with triamterene has good therapeutic effect.