A Focus on the Role of Dietary Treatment in the Prevention of Retinal Dysfunction in Patients with Long-Chain 3-Hydroxyacyl-CoA Dehydrogenase Deficiency: A Systematic Review.

Background: Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is an inborn error affecting fatty acid β-oxidation (FAO). Differently than other FAO deficiencies, LCHADD patients may develop progressive retinopathy and peripheral neuropathy. The pathogenesis of retinopathy is not completely understood, and the role of dietary interventions in preventing the development of retinopathy remains uncertain. We examined the literature to assess the impact of the dietary management of LCHADD patients on retinopathy prevention. Methods: Our systematic search included studies published in the last 20 years according to PRISMA guidelines. The aims of the review were to analyze the correlation between retinopathy and the following: (1) age at first metabolic decompensation and/or at the start of the dietary treatment, (2) chronic dietary treatment, (3) emergency regimens, (4) other nutritional supplements. The protocol was registered in PROSPERO, and evidence was assessed using the GRADE system. Results: Seven full papers were identified according to search criteria, with only four including meaningful data. Early presentation of the disease, acute neonatal symptoms, and a suboptimal chronic treatment control were associated with more aggressive retinopathy and a poorer sight outcome. The number of metabolic decompensations and/or hospitalizations were also positively correlated with vision loss. Chronic fat modulation in the diet had less impact than emergency treatments. The role of other nutritional supplements was not well defined. Conclusions: Newborn screening may improve retinal outcomes. Nevertheless, early treatment adopting the current LCHADD therapeutic regimen can often only delay the onset of retinopathy. Clearly, our current treatment strategies are not adequate and retina-specific treatments are needed. The optimal composition of the diet, the role of fasting limitation, and the benefits of some nutritional supplements deserve further investigations.