Combined isobutyryl-CoA and multiple acyl-CoA dehydrogenase deficiency in a boy with altered riboflavin homeostasis.

In this report, we describe the case of an 11-year-old boy, who came to our attention for myalgia and muscle weakness, associated with inappetence and vomiting. Hypertransaminasemia was also noted, with ultrasound evidence of hepatomegaly. Biochemical investigations revealed acylcarnitine and organic acid profiles resembling those seen in MADD, that is, multiple acyl-CoA dehydrogenase deficiencies (OMIM #231680) a rare inherited disorder of fatty acids, amino acids, and choline metabolism. The patient carried a single pathogenetic variant in the ETFDH gene (c.524G>A, p.Arg175His) and no pathogenetic variant in the riboflavin (Rf) homeostasis related genes (SLC52A1, SLC52A2, SLC52A3, SLC25A32, FLAD1). Instead, compound heterozygosity was found in the ACAD8 gene (c.512C>G, p.Ser171Cys; c.822C>A, p.Asn274Lys), coding for isobutyryl-CoA dehydrogenase (IBD), whose pathogenic variants are associated to IBD deficiency (OMIM #611283), a rare autosomal recessive disorder of valine catabolism. The c.822C>A was never previously described in a patient. Subsequent further analyses of Rf homeostasis showed reduced levels of flavins in plasma and altered FAD-dependent enzymatic activities in erythrocytes, as well as a significant reduction in the level of the plasma membrane Rf transporter 2 in erythrocytes. The observed Rf/flavin scarcity in this patient, possibly associated with a decreased ETF:QO efficiency might be responsible for the observed MADD-like phenotype. The patient's clinical picture improved after supplementation of Rf, l-carnitine, Coenzyme Q10, and also 3OH-butyrate. This report demonstrates that, even in the absence of genetic defects in genes involved in Rf homeostasis, further targeted molecular analysis may reveal secondary and possibly treatable biochemical alterations in this pattern.

Clinical presentation and molecular characterization of a novel patient with variant POC1A-related syndrome.

Biallelic pathogenic variants in POC1A result in SOFT (Short-stature, Onychodysplasia, Facial-dysmorphism, and hypoTrichosis) and variant POC1A-related (vPOC1A) syndromes. The latter, nowadays described in only two unrelated subjects, is associated with a restricted spectrum of variants falling in exon 10, which is naturally skipped in a specific POC1A mRNA. The synthesis of an amount of a POC1A isoform from this transcript in individuals with vPOC1A syndrome has been believed as the likely explanation for such a genotype-phenotype correlation. Here, we illustrate the clinical and molecular findings in a woman who resulted to be compound heterozygous for a recurrent frameshift variant in exon 10 and a novel variant in exon 9 of POC1A. Phenotypic characteristics of this woman included severe hyperinsulinemic dyslipidemia, acanthosis nigricans, moderate growth restriction, and dysmorphisms. These manifestations overlap the clinical features of the two previously published individuals with vPOC1A syndrome. RT-PCR analysis on peripheral blood and subsequent sequencing of the obtained amplicons demonstrated a variety of POC1A alternative transcripts that resulted to be expressed in the proband, in the healthy mother, and in controls. We illustrate the possible consequences of the two POC1A identified variants in an attempt to explain pleiotropy in vPOC1A syndrome.