A 9-month-old male presents with failure to thrive. Over his life, he has fallen below the growth curve on both length and weight. A dietary history reveals good intake (130-150cc/kg/day plus some solids), but delayed development. He is not sitting on his own and has trouble with truncal control, but he does have head control. Aside from appearing small and delayed, his exam is normal.
At previous visits, the following information has been obtained: CBC is normal without evidence of anemia. A CXR is normal, including a normal cardiac silhouette. A sweat chloride is normal and the child’s newborn screen is entirely normal.
Today, the basic metabolic panel shows a sodium of 140, a potassium of 2.3, a chloride of 114, a bicarbonate of 12, BUN of 16 and creatinine of 0.4. A venous blood gas confirms acidosis with a pH of 7.21. Urinanalysis shows a pH of 7.0, and 1-4 white cells, but is otherwise normal. You ask for urine electrolytes which yield a urine sodium of 48, potassium of 18, and chloride of 30.
What is your diagnosis?
This question appears in Med-Challenger Pediatric Medicine Exam Review with CME
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