Antenatal Ultrasound Findings in Spinal Muscular Atrophy Type 0

Area of Science:

• Genetics and Molecular Biology
• Prenatal Diagnosis
• Pediatric Neurology

Background:

• Spinal muscular atrophy (SMA) is a genetic disorder caused by SMN gene variants, leading to infant mortality.
• Previous studies on fetal SMA prenatal findings are inconsistent, potentially due to not considering SMN2 copy number.

Purpose of the Study:

• To analyze distinct prenatal findings in severe SMA type 0.
• To correlate prenatal sonogram findings with SMN2 copy number.

Main Methods:

• Case report of a neonate with SMA type 0 (0SMN1/1SMN2 genotype).
• Review of prenatal findings including hypoplastic left heart syndrome, AV block, nuchal translucency, and polyhydramnios.
• Literature search for prenatal findings in 32 cases of SMA type 0.

Main Results:

• Common associations in SMA type 0 include cardiac defects, increased nuchal translucency, and decreased fetal movement.
• Other findings include nonvertex presentation, polyhydramnios, and postnatal contractures/fractures.
• The case presented with HLHS, AV block, thickened nuchal translucency, and polyhydramnios.

Conclusions:

• Prenatal onset SMA type 0 with one SMN2 copy has a distinct phenotype.
• Frequent prenatal indicators are cardiac anomalies, increased nuchal translucency, and decreased fetal movement.
• These findings warrant SMA genetic testing.