A patient presents with mild mucocutaneous bleeding. Platelet count is normal. Bleeding time is prolonged. Platelet aggregation studies show a decreased second wave of aggregation with ADP and epinephrine. Electron microscopy shows a marked reduction in dense granules. Which substance is deficient in the affected granules?
- A ADP and ATP ✓
- B Fibrinogen
- C von Willebrand factor
- D Factor V
Correct answer: A. ADP and ATP
Explanation
Delta storage pool deficiency involves defective dense (delta) granules, which store ADP, ATP, calcium, and serotonin. ADP released from dense granules drives the second wave of platelet aggregation. Absent dense granules therefore cause a diminished second wave with ADP and epinephrine. Fibrinogen and factor V are in alpha granules, and vWF is in endothelial Weibel-Palade bodies.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.