Prenatal Diagnosis of Poretti-Boltshauser Syndrome: A Case of Live Birth with Confirmed LAMA1 Variants

Introduction: Poretti-Boltshauser syndrome (PBS; OMIM #615960) is a rare autosomal recessive neurodevelopmental disorder caused by biallelic pathogenic variants in the LAMA1 gene. It is characterized by cerebellar dysplasia with cyst formation, inferior vermian hypoplasia, and progressive visual impairment. Case presentation: Inferior vermian hypoplasia and right renal agenesis detected at 20 weeks' gestation on ultrasonography. Amniocentesis revealed a normal karyotype and chromosomal microarray. Trio whole-exome sequencing identified compound heterozygous LAMA1 variants. Parental segregation confirmed biallelic inheritance, establishing the diagnosis of PBS. A male infant was born at 38 weeks and 4 days. Postnatal evaluation showed bilateral cerebellar cortical irregularities with millimetric cysts on brain MRI, severe macular atrophy with punch-hole foveal lesions, global developmental delay, generalized hypotonia, and profound visual impairment. Conclusion This case expands the prenatal phenotype of PBS and highlights the diagnostic value of integrating advanced fetal imaging with trio whole-exome sequencing in fetuses presenting with posterior fossa abnormalities.