In which condition would a normal level of myoglobin be expected?

In which condition would a normal level of myoglobin be expected?

• A. Multiple myeloma
• B. Acute myocardial infarction
• C. Renal failure
• D. Crushing trauma

Answer: (A)

A normal myoglobin level is expected when there isn’t ongoing muscle injury. Myoglobin is released from skeletal and cardiac muscle when those tissues are damaged. In multiple myeloma, there isn’t injury to muscle tissue that would dump myoglobin into the bloodstream, so levels stay normal. In contrast, conditions like acute myocardial infarction damage heart muscle and release myoglobin early, and crushing trauma can cause rhabdomyolysis with substantial myoglobin release. Renal failure by itself may not elevate myoglobin unless there’s concurrent muscle breakdown or impaired clearance, but the classic reason for a normal myoglobin in this question is the absence of muscle injury in multiple myeloma.

A normal myoglobin level is expected when there isn’t ongoing muscle injury. Myoglobin is released from skeletal and cardiac muscle when those tissues are damaged. In multiple myeloma, there isn’t injury to muscle tissue that would dump myoglobin into the bloodstream, so levels stay normal. In contrast, conditions like acute myocardial infarction damage heart muscle and release myoglobin early, and crushing trauma can cause rhabdomyolysis with substantial myoglobin release. Renal failure by itself may not elevate myoglobin unless there’s concurrent muscle breakdown or impaired clearance, but the classic reason for a normal myoglobin in this question is the absence of muscle injury in multiple myeloma.