Autosomal Recessive Spastic Paraplegia Type 51 Caused by Homozygous Mutation of the AP4E1 Gene: A Case Report of a 17-Years-Old Boy

Autosomal recessive spastic paraplegia-51 (SPG51) is a rare neurodevelopmental disorder caused by a homozygous mutation in the AP4E1 gene, located on chromosome 15q21. Spastic paraplegia-51 (SPG51) is an extremely rare autosomal recessive neurodevelopmental disorder characterized by neonatal hypotonia that progresses to hypertonia and spasticity. Mutations in the AP-4E1 gene on chromosome 15q21.2, which is part of the AP-4 complex, can lead to autosomal recessive spastic paraplegia 51 (SPG51). Different mutations in this gene have been identified in affected individuals, leading to disruption of the AP4 complex and vesicular trafficking processes. The specific characteristics of SPG51 are, due to only few cases, not well understood due to limited reports of affected families. Affected individuals also have global developmental delay with impaired intellectual development and poor or absent speech. Studies linked to an additive symptom of persistent stuttering. Affected individuals typically present with hypotonia in the neonatal period, which progresses to muscular hypertonia, especially in the lower limbs. They may also exhibit contractures, talipes equinovarus, decreased muscle mass, short stature, and microcephaly. Severe mental retardation, absent speech, and dysmorphic facial features are common. Some patients may experience seizures. Neurological examination often reveals spastic paraplegia of the lower limbs, and brain imaging may show atrophy of the cerebellar vermis and cortical atrophy. We present an extremely rare case of a 17 years-old boy with autosomal recessive spastic paraplegia type 51.