The document presents a case report of a 42-year-old female who presented with tetany. Laboratory investigations revealed hypocalcemia, hypomagnesemia, and hypokalemic metabolic alkalosis. She was diagnosed with Gitelman's syndrome, a rare autosomal recessive condition characterized by those electrolyte abnormalities. Gitelman's syndrome results from mutations causing downregulation of the thiazide-sensitive sodium-chloride cotransporter in the distal convoluted tubule. Treatment involves magnesium and potassium supplementation.

1. An unusual ca(u)se of tetany Prof. S.SUNDAR’s unit, Dr. N.ARUN KUMAR, PG

10. Investigations CBC Values Hb TC DC ESR RBC HCT Platelet MCV MCH MCHC 11.8 gm% 11000 cells/cumm P51, L38, E6, M4, B1 4/10 4.4 million 34.9% 4.84 lakh 79.3 fl 26.8 pg 33.8 gm/dl

11. Electrolytes ELECTROLYTES VALUES Serum calcium- Serum magnesium Serum Na Serum K- Serum chloride Serum HCO3 Serum PTH Serum albumin 5.7 mg% (N – 8.7-10.2mg%) 1.2 mg% (N – 1.5-2.3mg%) 134 meq/L 2.92 meq/L 84 meq/L 34 meq/L 9.5 pg/ml (N – 8-51 pg/ml) 3.8gm/dl

16. Pathogenesis of Gitelman’s syndrome Inactivating mutations in the gene downregulation Hypocalciuria Due to associated Plasma volume contraction

17. Clinical features Gitelman’s syndrome is mostly a disorder of adults

18. Laboratory evaluation

20. Causes of hypocalcemia Low PTH levels High PTH levels Parathyroid agenesis isolated DiGeorge syndrome Vit. D def or impaired 1,25(OH)2 production/action nutritional vit.D def renal insufficiency with impaired 1,25(OH)2 production vit. D resistance Parathyroid destruction surgical radiation infiltration by mets auto immune PTH resistance syndromes PTH receptor mutations pseudo hypoparathyroidism Reduced parathyroid function hypomagnesemia activating CaSR mutations Drugs calcium chelators inhibitors of bone resorption (bisphosphonates, plicamycin) altered vit. D metabolism (phenytoin, ketoconazole) Miscellaneous causes acute pancreatitis acute rhabdomyolysis hyngry bone syndrome osteoblastic mets (Ca prostate)

21. Causes of hypocalcemia Associated with normal / low plasma PO4 Associated with high plasma PO4 Associated with hypoalbuminemia Vit. D def decreased intake decreased absorption (post-gastrectomy, PBC, intestinal malabsorption) Idiopathic or sporadic hypoparathyroidism Hemodilution Decreased 25(OH) vit. D generation (liver disease, anti- convulsants) Post operative hypo-parathyroidism Nephrotic syndrome Decreased calcitriol renal failure type 1 vit. D dep rickets Acquired hypo- parathyroidism post irradiation amyloidosis Exudative enteropathy Resistance to calcitriol type 2 vit. D dep rickets Pseudo hypo- parathyroidism type 1 type 2 cirrhosis Acute pancreatitis CKD advanced stage Mg deficiency AKI oligoanuric nstage

24. Trousseau’s sign: carpal spasm induced by inflation of BP cuff to >20 mmHg of systolic BP for 3 min

25. Chvostek’s sign: tapping of facial nerve branches  twitching of facial muscles)

26. Acute hypocalcemia paraesthesias of the lips & extremities muscle cramps tetany laryngeal stridor convulsions

27. Chronic hypocalcemia cataracts brittle nails with transverse grooves dry skin decreased or even absent axillary & pubic hair

29. Diagnostic approach to hypocalcemia

37. Goal of treatment To bring serum calcium to low normal range To avoid hypercalciuria To avoid nephrolithiasis