Peripheral Neuropathy: This is often the most common cause of numbness in a single limb, resulting from damage to the peripheral nerves, which can be due to various factors such as diabetes, vitamin deficiencies, or trauma.

Lumbar Radiculopathy: Numbness in the RLE could be due to compression or irritation of the nerve roots in the lumbar spine, often associated with lower back pain and sciatica.
Peripheral Artery Disease (PAD): Reduced blood flow to the lower extremities can cause numbness, pain, and weakness, especially during walking.
Morton's Neuroma: A condition that affects the nerves between the toes, causing numbness, pain, and tingling, typically in the forefoot area.

Spinal Cord Compression: A serious condition that requires immediate attention, where the spinal cord is compressed, potentially leading to permanent neurological damage if not promptly treated.
Deep Vein Thrombosis (DVT): A blood clot in the deep veins of the lower extremities, which can cause numbness, swelling, and warmth, and has a risk of leading to pulmonary embolism.
Aortic Aneurysm or Dissection: Although less common, these conditions can cause lower extremity numbness due to impaired blood flow and are medical emergencies.

Multiple Sclerosis: An autoimmune disease affecting the central nervous system, which can cause numbness in various parts of the body, including the lower extremities.
Guillain-Barré Syndrome: A rare autoimmune disorder where the body's immune system mistakenly attacks part of its peripheral nervous system, leading to numbness, weakness, and sometimes paralysis.
Vasculitis: Inflammation of the blood vessels, which can affect blood flow to the lower extremities and cause numbness, among other symptoms.