Severe Metabolic Acidosis in a Patient with Spinal Muscular Atrophy

Introduction: Ketogenesis starts early after starvation in healthy individuals. However, ketoacidosis develops after ~2 weeks of starvation. We report a case of severe ketoacidosis after a short period of fasting in a patient with spinal muscular atrophy (SMA). Case Description: A 59-year-old wheelchair-bound male with SMA and a recent history of percutaneous cholecystostomy presented to the hospital with purulent drainage. His food intake mainly comprised ground vegetables and protein. The patient was nil per oral overnight on day 2 for cholecystostomy tube exchange and reported abdominal pain and vomiting on day 3 of admission. Home medications included baclofen and sertraline. Physical examination was noted for muscle atrophy without any distress. Blood pressure was 124/66 mm Hg, pulse rate was 85/min, respiratory rate was 22/min, and oxygen saturation was 98% on room air. Laboratory evaluation: serum bicarbonate 11 mmol/L, anion gap 22, pH 7.17 with partial pressure of carbon dioxide of 30 on day 3 of admission. Severe high anion gap metabolic acidosis (without adequate respiratory compensation) was confirmed with repeat tests. Sodium bicarbonate infusion was started due to severe acidosis while being further evaluated. Serum creatinine was 0.49 m/dl, and electrolytes were within range. Serum lactate was 0.8 mmol/L (0.5 to 2 mmol/L), osmolar gap was 4 (<10), serum ethanol, methanol, ethylene glycol, salicylate, and acetaminophen, respectively, were negative. The urine dipstick showed 2+ ketones, serum acetone was 20 mg/dL (0-5 m/dL), and serum beta-hydroxybutyrate was 8.52 mmol/L (0.28 mmol/L). His blood sugar was 93 mg/dl on day 1 and 63 mg/dl on day 3 of admission. Low-normal blood sugar and ketoacidosis in the setting of ~18 hours of fasting prompted a diagnosis of starvation ketoacidosis. Serum bicarbonate remained ~12 mmol/L on bicarbonate infusion. Dextrose infusion normalized bicarbonate (25 mmol/L) within four hours. Discussion: Starvation ketoacidosis is described within 12-24 hours of starvation in patients with SMA in isolated case reports. Poor ketone body consumption by low muscle mass is postulated to cause severe ketoacidosis in SMA patients upon a short period of starvation. Timely treatment and prevention with dextrose, including during fasting for procedures, are crucial to prevent this complication in SMA patients.