Pitfalls in the Laboratory Diagnosis of Diabetic Ketoacidosis in Gitelman’s Syndrome

Gitelman’s syndrome (GS) is an autosomal recessive primary renal tubular disorder with hypokalemic metabolic alkalosis, hypocalciuria, and magnesium deficiency (1). The association of GS and type 1 diabetes is rare, and diabetic ketoacidosis (DKA) in GS has not been reported.

A 14-year-old male with known GS diagnosed at 5 years of age and type 1 diabetes diagnosed at 9 years of age was admitted to the hospital with nausea, vomiting, abdominal pain, and dehydration. Patient had history of omission of his insulin, potassium, and magnesium regimens. He was noted to be alert, afebrile, and tachycardic with normal respiration. Other clinical findings included a fruity breath odor, dry mucous membranes, and decreased skin turgor. Admission laboratory profile revealed the following: plasma glucose 555 mg/dl with strongly positive serum and urine ketones, arterial pH 7.37, calculated anion gap 34, serum sodium 134 mmol/l, potassium 2.2 mmol/l, bicarbonate 9 mmol/l, chloride 91 mmol/l, magnesium 1.3 mg/dl, and HbA_1c 10.3%. Electrocardiogram demonstrated sinus tachycardia and flat T-waves. Hospital management included restoration of intravascular volume and correction of serum electrolytes. Hyperglycemia, ketonemia, and the anion gap metabolic acidosis resolved after 2 days of intravenous insulin infusion. He was discharged after an extensive education focused on improving compliance with his prescribed therapy.

This is the first reported case of DKA in the setting of GS. In Gitelman’s variant of Bartter’s syndrome, a putative loss-of-function mutation in the thiazide-sensitive NaCl cotransporter located in the apical membrane of the distal convoluted tubule leads to polyuria, inappropriate kaliuresis, and hypomagnesemia (2). DKA has been described as the biochemical triad of hyperglycemia, ketonemia, and metabolic acidosis (3). The diagnosis of DKA can be confounded by the coexistence of combined acid-base disorders, where the metabolic acidosis is the less prominent component. The underlying chronic hypochloremic metabolic alkalosis associated with GS, compounded with acute vomiting, concealed the severe acute diabetic metabolic ketoacidosis on the initial presentation. This case presentation illustrates the importance of the anion gap calculation in the laboratory evaluation of DKA, where a misleading normal arterial pH due to a mixed acid-base disturbance may delay diagnosis, disposition, and optimal therapeutic interventions.