3-Hydroxyisobutyryl-CoA Hydrolase (HIBCH) Deficiency Cases Diagnosed by Only HIBCH Gene Analysis and Novel Pathogenic Mutation

Objective:

3-Hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency is a rare metabolic disease of valine metabolism. Only 22 cases of HIBCH deficiency have been reported in the literature. Our algorithm could help in the diagnosis of this disease.

Methods:

HIBCH gene analysis was performed in all cases.

Results:

The common features of our five patients from the same family with a developmental delay, seizures, and neurological regression were the elevation of 3-hydroxy-isobutyryl-carnitine and Leigh-like abnormalities. Unlike other patients in the literature, our patients were diagnosed with HIBCH gene analysis, rather than whole exome sequencing (WES). In all our cases, a missense c.452C>T, p. Ser151Leu homozygous novel pathogenic mutation was detected in the HIBCH gene.

Conclusion:

In cases where HIBCH deficiency is considered in our differential diagnosis algorithm, HIBCH gene analysis, which is cost-effective, should be performed instead of WES, and the number of cases should be increased in the literature.

MRI of 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency

3-Hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency is a rare mitochondrial disorder of valine metabolism which may present with motor delay, hypotonia, ataxia, dystonia, seizures poor feeding, and organic aciduria. Neuroimaging findings include signal abnormalities of the deep gray matter, particularly the globus pallidi, and cerebral peduncles. We report a 15-month-old male patient with HIBCH deficiency who presented with paroxysmal tonic upgaze of infancy, motor delay, and hypotonia. MRI revealed characteristic bilateral, symmetric signal abnormalities in the basal ganglia and a mutation in HIBCH was confirmed with whole exome sequencing. HIBCH should be a consideration in patients with Leigh-like features, especially if neuroimaging changes primarily affect the globus pallidi. Recognition of this pattern may help guide targeted testing and expedite the diagnosis and treatment of this rare disease.

A phenotypically severe, biochemically "silent" case of HIBCH deficiency in a newborn diagnosed by rapid whole exome sequencing and enzymatic testing

3-Hydroxyisobutyryl-CoA dehydrogenase (HIBCH) deficiency is a rare error in valine catabolism associated with a Leigh syndrome-like phenotype, mitochondrial dysfunction, and increased C4-OH. We report the most severe case to date in a full-term female who presented with poor feeding and nystagmus on day of life (DOL) 1. Although initial neuroimaging findings were concerning for metabolic disease, further metabolic testing was nondiagnostic and she was discharged on DOL 18. She was readmitted on DOL 22 after severe apneic episodes requiring intubation, with EEG demonstrating multifocal seizures and MRI/MRS demonstrating worsening findings. Care was withdrawn DOL 27 and she expired. Rapid whole exome sequencing (WES) demonstrated compound heterozygous variants in HIBCH with a paternal pathogenic variant (c.852delA, p.L284FfsX10) and a maternal likely pathogenic variant (c.488G>T, p.C163F). Fibroblast enzymatic testing demonstrated marked reduction in HIBCH levels. This case demonstrates the importance of rapid WES and follow-up functional testing in establishing a diagnosis when metabolic disease is suspected but lacks an expected biochemical signature.

A therapeutic regimen for 3-hydroxyisobutyryl-CoA hydrolase deficiency with exercise-induced dystonia

3-Hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency is a recently described disease resulting from mutations in HIBCH with no effective treatment. Here, we report a female Chinese patient presenting with exercise-induced dystonia and bilateral symmetrical hyperintensities of the globus pallidus on brain MRI associated with novel HIBCH mutations (c.1027C>G;p. H343D and c.383T>A;p.V128D). After treatment for 1 year with a low-valine diet, both clinical symptoms and brain lesions improved substantially. We propose that HIBCH deficiency should be considered in the differential diagnosis for patients with exercise-induced dystonia, particularly if bilateral symmetrical lesions in the globus pallidus are present. A low-valine diet is a potentially promising treatment for HIBCH deficiency.

3-Hydroxyisobutyryl-CoA hydrolase deficiency in an Iranian child with novel HIBCH compound heterozygous mutations

We report a patient presenting with developmental delay, Leigh-like abnormalities on MRI and elevated 3-hydroxyisovaleric acid levels. Upon whole-exome sequencing, he was diagnosed with 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) deficiency, and hence subjected to specific dietary treatment. HIBCH deficiency should be considered in the differential diagnosis of Leigh-like disease and/or organic aciduria.

Successful diagnosis of HIBCH deficiency from exome sequencing and positive retrospective analysis of newborn screening cards in two siblings presenting with Leigh's disease

PURPOSE

3-Hydroxyisobutryl-CoA hydrolase (HIBCH) deficiency is a rare disorder of valine metabolism. We present a family with the oldest reported subjects with HIBCH deficiency and provide support that HIBCH deficiency should be included in the differential for elevated hydroxy-C4-carnitine in newborn screening (NBS).

METHODS

Whole exome sequencing (WES) was performed on one affected sibling. HIBCH enzymatic activity was measured in patient fibroblasts. Acylcarnitines were measured by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Disease incidence was estimated using a cohort of 61,434 individuals.

RESULTS

Two siblings presented with infantile-onset, progressive neurodegenerative disease. WES identified a novel homozygous variant in HIBCH c.196C>T; p.Arg66Trp. HIBCH enzymatic activity was significantly reduced in patients' fibroblasts. Acylcarnitine analysis showed elevated hydroxy-C4-carnitine in blood spots of both affected siblings, including in their NBS cards, while plasma acylcarnitines were normal. Estimates show HIBCH deficiency incidence as high as 1 in ~130,000 individuals.

CONCLUSION

We describe a novel family with HIBCH deficiency at the biochemical, enzymatic and molecular level. Disease incidence estimates indicate HIBCH deficiency may be under-diagnosed. This together with the elevated hydroxy-C4-carnitine found in the retrospective analysis of our patient's NBS cards suggests that this disorder could be screened for by NBS programs and should be added to the differential diagnosis for elevated hydroxy-C4-carnitine which is already measured in most NBS programs using MS/MS.

HIBCH deficiency in a patient with phenotypic characteristics of mitochondrial disorders

HIBCH (3-hydroxyisobutyryl-CoA hydrolase) deficiency (MIM #250620) is a rare autosomal recessive inborn error of metabolism, leading to a block in the catabolic pathway of the amino acid valine and presumably to accumulation of toxic valine metabolites in mitochondria. Only three families with HIBCH deficiency and biallelic HIBCH mutations have been described. We report on a further patient, first child of healthy consanguineous parents, with severe developmental delay, seizures, hyperintensities of the basal ganglia on magnetic resonance imaging (MRI), progressive brain atrophy, optic nerve atrophy, repeatedly elevated blood lactate, and respiratory chain complexes I, I + III and cytochrome c oxidase deficiencies with borderline depletion of mitochondrial DNA in muscle tissue. Laboratory findings in blood and skeletal muscle were inconsistent and did not allow a definite diagnosis, but supported the hypothesis of mitochondrial dysfunction. Homozygosity mapping and whole-exome sequencing revealed a homozygous one-base pair insertion in HIBCH. Deficiency of enzyme activity was confirmed in cultured fibroblasts. Although relatively unspecific, the clinical features were similar to those of the previously reported cases. Given the clinical variability and large number of differential diagnoses, the prevalence of HIBCH deficiency is probably underestimated. Next-generation sequencing approaches are an effective tool for identifying the underlying genetic basis in patients suspected of mitochondrial disorders.