Genetic Metabolic Deficiency Syndromes

In Episode 26 of Med School Question of the Week for USMLE, Alisa Khomutova, MedSchoolCoach expert tutor, answers this medical school question: A 7-month-old boy is brought to the physician by his parents for slowly worsening loss of muscle control and sleepiness. They have noticed several episodes of unresponsiveness with a blank stare and fluttering of the eyelids. He does not maintain eye contact. He was able to roll over from front to back at 5 months of age and has not yet begun to sit or crawl. His parents are of Ashkenazi Jewish descent. Vitals are wnl. Neurological examination shows generalized hypotonia. Deep tendon reflexes are 3+bilaterally. Plantar reflex shows extensor response bilaterally. Fundoscopy shows bright red macular spots in both eye. During the exam, the physician accidentally drops the tuning fork and the infant startles. Which of the following is the most likely case of this patient’s symptoms?

• Arylsulfatase A deficiency
• Spingomyelinase deficiency
• Alpha galactosidase deficiency
• Beta glucocerebrosidase deficiency
• Beta hexosaminidase deficiency
• Galactocerebrosidase deficiency