L-3-hydroxyacyl-CoA dehydrogenase deficiency: two cases with pigmentary retinopathy

The Finnish genetic heritage in 2022 – from diagnosis to translational research

Isolated populations have been valuable for the discovery of rare monogenic diseases and their causative genetic variants. Finnish disease heritage (FDH) is an example of a group of hereditary monogenic disorders caused by single major, usually autosomal-recessive, variants enriched in the population due to several past genetic drift events. Interestingly, distinct subpopulations have remained in Finland and have maintained their unique genetic repertoire. Thus, FDH diseases have persisted, facilitating vigorous research on the underlying molecular mechanisms and development of treatment options. This Review summarizes the current status of FDH, including the most recently discovered FDH disorders, and introduces a set of other recently identified diseases that share common features with the traditional FDH diseases. The Review also discusses a new era for population-based studies, which combine various forms of big data to identify novel genotype–phenotype associations behind more complex conditions, as exemplified here by the FinnGen project. In addition to the pathogenic variants with an unequivocal causative role in the disease phenotype, several risk alleles that correlate with certain phenotypic features have been identified among the Finns, further emphasizing the broad value of studying genetically isolated populations.

Ocular characteristics in 10 children with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency: a cross-sectional study with long-term follow-up

PURPOSE

To present long-term ocular complications and electroretinographic (ERG) findings in children with long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency - a life-threatening metabolic disease - and the relation to age at diagnosis, treatment and other clinical parameters.

METHODS

Ten children with LCHAD deficiency underwent repeated ophthalmological evaluations including ERG.

RESULTS

All 10 children developed chorioretinal pathology. Regardless of age at diagnosis, initiation of treatment and age at examination, inter-individual differences were present. Profound chorioretinal atrophy, severe visual impairment and progressive myopia had developed in two teenagers. Milder chorioretinopathy with or without subnormal visual acuity was present in all other children. ERG was pathological in seven children. The chorioretinopathy often started in the peripapillary or perimacular areas. In one patient, unilateral visual impairment was associated with fibrosis.

CONCLUSION

Early diagnosis and adequate therapy might delay but not prevent the progression of retinal complications. Late diagnosis with severe symptoms at diagnosis, neonatal hypoglycaemia and frequent decompensations may increase the progression rate of the chorioretinopathy. LCHAD deficiency, a potentially lethal disease, is sometimes difficult to diagnose. Unusual chorioretinal findings should alert the ophthalmologist to the long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency, especially if there is a history of neonatal hypoglycaemia or failure to thrive.

Polyunsaturated fatty acid deficiency during dietary treatment of very long-chain acyl-CoA dehydrogenase deficiency. Rescue with soybean oil

Nutritional management of very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is based on the avoidance of fasting and substitution of medium-chain triglycerides for long- and very long-chain triglycerides. We report two cases of this disease, which developed omega-6 essential fatty acid deficiency after three and five months from the beginning of nutritional therapy (SHS product: Monogen). This alteration could be especially dangerous in these patients owing to their possible susceptibility to the development of pigmentary retinopathy. The incorporation of linoleic acid as 3-4% of total caloric intake supported as soybean oil ameliorates this deficiency. We wish to remark on this early complication in the nutritional management of VLCAD deficiency and the possibility of rescue by the incorporation of soybean oil into the diet.