Cystic Fibrosis Presenting as Pseudo-Bartter Syndrome: An Important Diagnosis that is Missed!
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REVIEW ARTICLE
Cystic Fibrosis Presenting as Pseudo-Bartter Syndrome: An Important Diagnosis that is Missed! Mohsin Raj Mantoo 1 & Madhulika Kabra 1 & S. K. Kabra 1 Received: 14 January 2020 / Accepted: 6 May 2020 # Dr. K C Chaudhuri Foundation 2020
Abstract Cystic fibrosis (CF), an autosomal recessive disorder, occurs due to mutations in CFTR gene resulting in impaired cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel function in various epithelia. In addition to the well-known pulmonary and pancreatic morbidities, CF is characterized by electrolyte and acid-base abnormalities- hypochloremia, hyponatremia, hypokalemia and metabolic alkalosis. These are collectively known as Pseudo-Bartter syndrome, as similar abnormalities are seen in Bartter syndrome- an inherited tubulopathy affecting thick ascending limb of loop of Henle. There may be a significant clinical overlap between the Classic Bartter syndrome, Gitelman syndrome and CF presenting as Pseudo-Bartter syndrome, especially in early childhood. This review focuses on Pseudo-Bartter syndrome in CF, its pathogenesis and differentiation from Bartter/Gitelman syndrome. Other causes of metabolic abnormalities resembling Bartter syndrome are also highlighted. Keywords Cystic fibrosis . Hypokalemia . Hyponatremia . Metabolic alkalosis
Introduction Cystic fibrosis and Bartter syndrome are rare inherited disorders. Overlapping of some clinical manifestations like dehydration and failure to thrive, and similar electrolyte abnormalities in the two conditions may create a diagnostic confusion. This is more common during infancy and early childhood.
Representative Case Case N, a 4-month-old female infant, presented with failure to thrive, recurrent dehydration and one episode of pneumonia; requiring hospitalization thrice. Infant was severely malnourished with weight of 2.6 kg. Chest X-ray was normal; blood investigations revealed significant abnormalities in electrolyte and acid base balance (serum sodium 126 mEq/L, potassium 1.8 mEq/L, blood pH 7.52 and bicarbonate 32 mmol/L) along with raised urea and creatinine (urea 76 mg/dl and creatinine 1.4 mg/dl). A diagnosis of Bartter syndrome was made and the * S. K. Kabra [email protected] 1
Department of Pediatrics, All India Institute of Medical Sciences, New Delhi 110029, India
child was sent to authors’ hospital for further management. In view of one episode of pneumonia and history of frequent foul-smelling stools, a diagnosis of cystic fibrosis was considered and sweat chloride was performed. Cystic fibrosis was confirmed with sweat chloride of 130 mEq/L and CFTR mutation analysis revealed homozygous for delta F 508 mutation. The infant was treated with intravenous infusion of normal saline, potassium and other supportive care for cystic fibrosis. Electrolyte abnormalities, metabolic alkalosis, blood urea and creatinine improved in 36 h. The infant was again hospitalized later with dehydration and similar electrolyte abnormalities. This case highlights the overlapping clinical symptoms,
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