3-Methylglutaconic aciduria type 1 (MGCA1) is an inborn error of leucine catabolism caused by pathogenic variants of the AUH gene. MGCA1 can be identified by newborn screening (NBS) with elevated C5-OH levels. We herein report a girl with MGCA1 detected by NBS. On day 5 after birth, NBS detected high C5-OH levels of 1.17 μmol/L (1.56 μmol/L [retest]). A urinary organic acid analysis revealed the abnormal excretion of 3-methylglutaconic, 3-methylglutaric, and 3-hydroxyisovaleric acids. Two novel heterozygous loss-of-function variants in the AUH gene were identified by genetic testing. We observed the patient without any treatment, such as a leucine-restricted diet. She had episodes of febrile illness several times in infancy but did not develop febrile convulsions or encephalopathy. She is now two years and six months old, and her physical growth and psychomotor development have progressed normally. In a review of the literature and our case, four children with MGCA1 identified during the neonatal period were asymptomatic or exhibited speech delay, regardless of whether or not they had been managed with specific treatments. Treatments such as dietary leucine restriction and carnitine supplementation may have little effect on MGCA1 in childhood; however, further investigation is warranted to evaluate the benefits of specific treatments to prevent potential long-term neurological complications.

3-methylglutaconic aciduria type 1 (3-MGA-I) (MIM ID #250950) is an ultra-rare, autosomal recessive organic aciduria, resulting from mutated AUH gene, leading to the deficient 3-methylglutaconyl-CoA hydratase (3-MGH). Only around 40 cases are previously reported, caused by a spectrum of 10 mutations. The clinical spectrum of 3-MGA-I in children is heterogeneous, varying from asymptomatic individuals to mild neurological impairment, speech delay, quadriplegia, dystonia, choreoathetoid movements, severe encephalopathy, psychomotor retardation, basal ganglia involvement. Early dietary treatment with leucine restriction and carnitine supplementation may be effective in improving neurological state in pediatric patients with 3-MGA-I. We presented a girl with 3-MGA-I due to novel AUH gene mutation (homozygous variant c.330 + 5G > A) and confirmed by almost undetectable 3-MGH-enzyme activity, who initially presented with central precocious puberty at an early age of 4.5 years. Precocious puberty might be associated with the 3-MGA-I, as is reported previously in some other metabolic disorders that result in pathologic accumulation of metabolites or toxic brain damage. Therapy with GnRH agonist triptorelin effectively arrested pubertal development.

3-Methylglutaconic aciduria is a member of inborn errors of leucine metabolism pathway. 3-Methylglutaconic aciduria type I (MGA1) causes neurological problems which are present during infancy or childhood but the diagnosis may be delayed until adulthood. Here we report a 3years old patient with developmental delay from a relative parent's that his medical evaluations include analyses of urinary organic acid and blood acylcarnitine showed high level of 3-methylglutacoic acid, 3-hydroxyisovaleric acid and increased level of 3-hydroxyisovalerylcarnitine respectively. Further evaluation and genetic tests revealed a novel homozygous mutation of variant c.179del G (p.Gly60Valfs*12) in exon 1 of the AUH gene that was compatible with the diagnosis of MGA1. In segregation analysis of his family, both parents were heterozygous for the respective mutation, confirming obligate parental carrier status and segregation of the mutation.