Enter your email to get your 85% OFF code and unlock the full USMLE question bank on the app.
Free notes, MCQs, tables & flowcharts for USMLE Step 3 Biochemistry
You examine an infant in your office. On exam you observe hypotonia, as well as the findings shown in Figures A and B. You order laboratory testing, which demonstrates the findings shown in Figure C. Which of the following is the most likely pathologic mechanism involved?
AAccumulation of galactocerebroside
BAccumulation of ceramide trihexoside
CAccumulation of GM2 ganglioside
DAccumulation of glucocerebroside
EAccumulation of sphingomyelin
A 7-month-old boy is brought by his parents to the pediatrician’s office. His mother says the child has been weakening progressively and is not as active as he used to be when he was born. His condition seems to be getting worse, especially over the last month. He was born at 41 weeks through normal vaginal delivery. There were no complications observed during the prenatal period. He was progressing well over the 1st few months and achieving the appropriate milestones. On examination, his abdomen appears soft with no liver enlargement. The patient appears to be dehydrated and lethargic. The results of a fundoscopic examination are shown in the picture. A blood test for which of the following enzymes is the next best assay to evaluate this patient's health?
AAcid alpha-glucosidase
BHexosaminidase
CSphingomyelinase
DGlucocerebrosidase
EArylsulfatase A
An 8-month-old boy is brought to the physician by his parents for gradually increasing loss of neck control and inability to roll over for the past 2 months. During this time, he has had multiple episodes of unresponsiveness with a blank stare and fluttering of the eyelids. His parents state that he sometimes does not turn when called but gets startled by loud noises. 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. Neurological examination shows generalized hypotonia. Deep tendon reflexes are 3+ bilaterally. Plantar reflex shows extensor response bilaterally. Fundoscopy shows bright red macular spots bilaterally. The remainder of the examination shows no abnormalities. Which of the following is the most likely cause of this patient's symptoms?
ASphingomyelinase deficiency
Bβ-glucocerebrosidase deficiency
Cα-galactosidase A deficiency
DATP-binding cassette transporter mutation
Eβ-hexosaminidase A deficiency
+ 7 more in the PDF
Browse all chapters