Make the Diagnosis: Spring 2016

A previously healthy 3-year-old boy was brought to the Emergency Department (E.D.) because of a change in mental status and diarrhea. The child was born full-term and was healthy until 6 months prior to admission, when he started to gain weight rapidly. His weight jumped from the 25th to the 99th percentile. At that time, a sodium level was 165 mmol/L, but a repeat level was 145 mmol/L. A month before admission, he developed behavioral issues including cursing, spitting, and throwing soiled diapers. A few days before admission, he developed mild diarrhea. On the day of admission, his speech was slurred, prompting his trip to the E.D. He underwent a brain MRI with sedation. The MRI was normal, but the patient developed severe desaturation and bradycardia, and was intubated and transferred to the PICU. On examination in the PICU, the patient was obese (24 kg, BMI > 99th percentile) and appeared mildly dehydrated. Lungs were clear and heart sounds were normal. He was sedated, but the neurologic exam was otherwise normal. A chest X-ray showed scattered areas of atelectasis. Electrolytes revealed a sodium of 183, potassium 4.1, chloride 143, carbon dioxide 25, BUN 33, and creatinine 0.8. A blood gas while the patient was intubated on CPAP of 6 cm H₂O and minimally sedated revealed a pH of 7.41, PCO₂ 61, and PO₂ 98.

What is the diagnosis?

No one submitted the correct answer to last issue’s challenge. The correct answer was arrhythmogenic right ventricular cardiomyopathy (ARVC), the subject of this issue’s cover story.