3-Hydroxyisobutyric acid (3HiB) is an intermediate in the degradation of the branched-chain amino acid valine. Disorders in valine degradation can lead to 3HiB accumulation and its excretion in the urine. This article describes the first two patients with a new metabolic disorder, 3-hydroxyisobutyrate dehydrogenase (HIBADH) deficiency, its phenotype and its treatment with a low-valine diet. The detected mutation in the HIBADH gene leads to nonsense-mediated mRNA decay of the mutant allele and to a complete loss-of-function of the enzyme. Under strict adherence to a low-valine diet a rapid decrease of 3HiB excretion in the urine was observed. Due to limited patient numbers and intrafamilial differences in phenotype with one affected and one unaffected individual, the clinical phenotype of HIBADH deficiency needs further evaluation.

中文翻译：

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3-羟基异丁酸脱氢酶 (HIBADH) 缺乏症——一种新的缬氨酸代谢紊乱

3-羟基异丁酸 (3HiB) 是支链氨基酸缬氨酸降解的中间体。缬氨酸降解障碍可导致 3HiB 积累及其在尿液中的排泄。本文描述了前两名患有新的代谢紊乱，3-羟基异丁酸脱氢酶 (HIBADH) 缺乏症的患者，其表型和低缬氨酸饮食的治疗。HIBADH中检测到的突变基因导致突变等位基因的无义介导的mRNA衰变和酶的完全丧失功能。在严格遵守低缬氨酸饮食的情况下，观察到尿液中 3HiB 排泄的迅速减少。由于患者数量有限，以及一个受累和一个未受累个体的家族内表型差异，HIBADH 缺乏症的临床表型需要进一步评估。