The parents of a 7-month-old boy bring their son to the pediatrician because they have noticed that their child has a dull response to outside stimuli. In addition, they note that their child exhibits an exaggerated startle response (sudden extension of arms and legs) to sharp sounds and that he seems to be losing previously acquired motor and mental skills. The symptoms observed in this infant are most indicative of which of the following disorders?

Question

Quizplus · Accepted Answer

The symptoms described, such as the exaggerated startle response and loss of motor and mental skills, are characteristic of Tay-Sachs disease, a genetic disorder caused by a deficiency of the enzyme hexosaminidase A. Infants with Tay-Sachs disease appear normal at birth. Symptoms usually begin with mild motor weakness by 3 to 5 months of age. Parents will begin to notice that their afflicted child has a dull response to outside stimuli. Another early symptom is an exaggerated startle response. By 6 to 10 months of age infants will begin to show regression of prior acquired motor and mental skills. It is the loss of these activities that will normally prompt parents to seek a medical opinion. A progressive loss in visual attentiveness may lead to an ophthalmological consultation which will reveal macular pallor and the presence of the characteristic "cherry-red spot" on the fundus of the eye.

The Parents of a 7-Month-Old Boy Bring Their Son to the Pediatrician