5th February 2024

A 1-year-old male presents to the genetic clinic with a developmental delay.

A 1-year-old male presents to the genetic clinic with a developmental delay. He had normal development and examination up to 4 months old. Since then, he has not attained his usual developmental milestones and has become increasingly hypotonic. He cannot hold his head unsupported, which he could previously carry out independently. His mother reports poor sleep. He developed a generalised tonic-clonic seizure one week prior to his clinic appointment. 

Examination today showed myoclonic jerks. The patient had poor head control with generalised hypertonia with weakness of 3/5 throughout all muscle groups. Ophthalmoscopy exam reveals bilateral cherry red spots. 

Which of the following enzyme deficiency is associated with this condition?