Subacture combined degeneration of cord is caused due to deficiency of –
**Core Concept**
Subacute combined degeneration of the cord is a neurological disorder characterized by progressive damage to the spinal cord. This condition is primarily associated with a deficiency of **vitamin B12**, which plays a crucial role in the synthesis of **myelin** and the maintenance of the nervous system.
**Why the Correct Answer is Right**
The correct answer is related to the deficiency of **vitamin B12**, as it is essential for the production of **methionine** from **homocysteine** via the **methionine synthase** reaction. This process is vital for the synthesis of **myelin** and the maintenance of the nervous system. A deficiency in **vitamin B12** leads to impaired **myelin** synthesis, resulting in demyelination and axonal damage in the spinal cord.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not directly related to the pathogenesis of subacute combined degeneration of the cord.
**Option B:** Similarly, this option is incorrect as it does not play a primary role in the development of this condition.
**Option C:** This option is also incorrect as it is not the primary deficiency associated with subacute combined degeneration of the cord.
**Clinical Pearl / High-Yield Fact**
Subacute combined degeneration of the cord is a classic complication of **vitamin B12 deficiency**, often presenting with symptoms such as weakness, gait disturbances, and sensory deficits. Early recognition and treatment with **vitamin B12 supplementation** can prevent long-term neurological damage.
**Correct Answer:** D. Vitamin B12 deficiency