A 53-Year-Old Man With Peripheral Neuropathy: Osmosis USMLE Study Question

April 30, 2021

Diabetic peripheral neuropathy is typically characterized by a distal symmetric neuropathy that affects sensory nerves in a "stocking/glove" distribution. Typically, it involves numbness and paresthesias that can be painful to light touch and develop into severe "burning pain" especially at night, making it difficult to sleep. Over time, the loss of sensation leads to ulcer formation (due to patients not shifting weight) with subsequent ischemia of pressure point areas. The underlying mechanism involves the activity of the enzyme aldose reductase, which converts glucose into sorbitol.

This conversion traps the molecule of sorbitol (previously glucose) inside of the cell; however, if sorbitol accumulates (due to a relative deficiency in sorbitol dehydrogenase), the resulting elevated levels of sorbitol can cause osmotic damage. This mechanism is responsible for diabetic complications seen with chronic hyperglycemia, including cataracts, retinopathy, and peripheral neuropathy.

Major Takeaway: Diabetic peripheral neuropathy results from osmotic damage to neurons that occurs as a result of elevated sorbitol levels in the cell.

Read more clinical information on diabetic neuropathy.

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