Diabetic Neuropathy: This is the most common cause of polyneuropathy, especially when symptoms start in the lower extremities and progress proximally. Diabetes mellitus is a widespread condition, and its neuropathy often presents with sensory symptoms such as numbness, tingling, and pain in a stocking-and-glove distribution.

Alcoholic Neuropathy: Chronic alcohol abuse can lead to a similar pattern of neuropathy, with symptoms including weakness, numbness, and pain in the legs, which can progress to the arms. Nutritional deficiencies, particularly thiamine deficiency, contribute to this condition.
Vitamin B12 Deficiency: A deficiency in vitamin B12 can cause a neuropathy that starts in the lower extremities and moves proximally, often accompanied by other symptoms such as fatigue, weakness, and neurological changes.
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP): An autoimmune disorder that causes progressive weakness and loss of sensation, typically starting in the distal limbs and progressing proximally. It can resemble Guillain-Barré syndrome but has a more chronic course.

Guillain-Barré Syndrome: Although it typically presents with rapid progression of weakness, it's crucial not to miss this diagnosis due to its potential for respiratory failure and the need for urgent treatment. The pattern can start distally and move proximally.
Amyloidosis: A condition where abnormal proteins (amyloid) accumulate in various organs, including nerves, leading to neuropathy. It can present with a variety of symptoms, including neuropathic pain, weakness, and autonomic dysfunction.
Heavy Metal Poisoning (e.g., Lead, Arsenic): Exposure to heavy metals can cause a neuropathy that may start in the lower extremities. These conditions are less common but can have significant health implications if not identified and treated.

Tangier Disease: A rare inherited disorder characterized by significantly low levels of HDL cholesterol and the accumulation of cholesterol in various body tissues, including nerves, leading to neuropathy.
Familial Amyloid Polyneuropathy (FAP): A rare group of genetic disorders caused by mutations in the TTR gene, leading to the accumulation of amyloid in peripheral nerves and other organs.
Porphyria: A group of rare genetic disorders that can cause neuropathy among other symptoms, due to the accumulation of porphyrins or their precursors. Neuropathic pain and weakness are common presentations.