Fetal Cranial Biometric Abnormalities: The Value of Routine Ultrasound for Early Diagnosis of Glutaric Acidemia Type 1

OBJECTIVE: Glutaric acidemia type 1 (GA-1) is a severe, life-threatening organic acidemia. This study aimed to evaluate fetal ultrasound findings as early clues for GA-1. METHODS: A GA-1 case identified via newborn screening in Beijing and confirmed by exome sequencing was analyzed. His prenatal ultrasound records were retrospectively reviewed. A scoping review was performed following PRISMA-ScR guidelines to identify fetal GA-1 cases with prenatal imaging data from PubMed, Embase, and Scopus. Findings were summarized using the terminology reported in the original publications. RESULTS: In the present case, both biparietal diameter (BPD) and head circumference (HC) exceeded the 97th percentile by 32 + 1 week of gestation. At 36 + 1 week, BPD remained above the 97th percentile, while HC was near it. Genetic analysis revealed two novel heterozygous GCDH variants: c.492C > G and c.648G > A. The scoping review identified six fetal GA-1 cases. Reported prenatal abnormalities included macrocephaly (5/6), enlarged Sylvian fissures (3/6), temporal lobe hypoplasia (2/6), cerebrospinal fluid (CSF) widening in the temporal fossa (1/6), and subependymal cysts (2/6). CONCLUSIONS: Specific prenatal cranial findings, particularly fetal macrocephaly, may serve as early clues for GA-1. The diagnostic indication is strengthened when macrocephaly coexists with features such as Sylvian fissure widening. Recognition of these features could facilitate earlier identification and diagnosis of GA-1.