Transient bilateral vision loss during acute metabolic decompensation in a patient with methylmalonic acidemia
2Specialty School of Pediatrics, Alma Mater Studiorum, University of Bologna, Italy
3The Pediatric Unit, Maternal and Child Department, Guglielmo da Saliceto Hospital, Italy
Background: Classical methylmalonic acidemia (MMA) is a rare metabolic disorder manifesting early in life with acute metabolic distress (AMD) and often resulting in late-onset dysfunction in several organ systems, including optic neuropathies and atrophies.
Case Study: A patient affected by MMA experienced a temporary complete bilateral visual loss after an AMD.
Results: A 9-years-old male (with MMA_Mut0) was admitted to the hospital for vomiting and dehydration. He showed severe lactic acidosis, with elevated urinary (MMA 1251 mM/mcU) without hyperammoniemia. The patient underwent suspension of protein intake and increase in glucose support, bicarbonate boluses. Neverthless, due to the worsening of metabolic acidosis, he was admitted to the pediatric intensive care unit and started continuous venovenous haemofiltration (CVVH). Lactic acidosis gradually improved and resolved in 24 hours. At that time, he rapidly developed a bilateral visual loss, photophobia and a fixed mydriasis unresponsive to the light stimulus which persisted after the normalization of blood gases and normalization of plasmatic levels of inotropes. The clinic ophthalmic examination and the visual evoked potential were negative. MRI confirmed thinning of the posterior tracts of the optic nerves which was already reported in the patient. Due to the persistence of vision loss for 2 weeks, the patient started coenzyme Q10 (10 mg/kg/d) combined with vitamin E (10 mg/kg/d) treatment. The patient gradually regained his visual acuity within 4 weeks.
Discussion/Conclusion: The sudden visual loss in our patient was probably induced by neurotoxicity and oxidative stress. We argued that in our patient an excessive administration of intravenous glucose eventually caused the overwhelming lactic acidosis. Elimination of lactic acidemia by CVVH was the key factor to rescue the patient, however visual impairment was a severe complication that needed several weeks to improve.
.png)