The first case with FBXL4 mutation successfully treated with a parenteral ketogenic diet for lactic acidosis.

Background: The ketogenic diet (KD) is a low-carbohydrate, high-fat diet that has been used as an effective nonpharmacological treatment in many neurological and metabolic disorders for a long time. The effectiveness of the KD is revealed in mitochondrial disorders, mainly in pyruvate dehydrogenase deficiency.

Case report: A 4-year-old girl who was diagnosed with an F-box and leucine-rich repeat protein 4 (FBXL4) gene mutation was hospitalized with sepsis. She was first given standard parenteral nutrition (PN) because of gastrointestinal problems. During the disease course, lactic acidosis became prominent and did not respond to pharmacological treatment; standard PN was gradually switched to parenteral KD, and lactate levels decreased after parenteral KD. The patient was discharged with an enteral KD.

Conclusion: This is the first case of mitochondrial depletion syndrome effectively treated with parenteral KD for lactic acidosis.