Polyneuropathies are diseases of the peripheral nerves when peripheral nerves are affected in groups and in varying patterns. These diseases result in various clinical expressions of diseased nerves. Polyneuropathies are classified according to their clinical picture and underlying pathology. Here is an account of types and causes of polyneuropathies.
1. Sensory Motor Polyneuropathy:

This type of nerve diseases affect both sensory and motor nerves resulting in loss of both sensations and muscle power. These can be caused by following:
I. Alcohol
II. Diabetes Mellitus
III. Hypothyroidism
IV. Guillain-Barre Syndrome (GBS)
V. Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)
VI. Hereditary Motor & Sensory Neuropathy (HMSN)
VII. Vasculitis
VIII. Paraneoplastic Neuropathy
IX. Paraproteinemic Neuropathy
2. Sensory Polyneuropathy:

Only sensory nerves are affected by sensory polyneuropathy, resulting in loss of sensations only while muscle power remains preserved. Here is a list of causes of sensory polyneuropathy:
I. Diabetes Mellitus
II. Hypothyroidism
III. Drugs, such as isoniazid and vincristine
IV. Vitamin B12 deficiency
V. Paraneoplastic
VI. Amyloidosis
VII. HIV
VIII. Leprosy
3. Motor Polyneuropathy:

Only motor nerves are affected in this variety resulting in weakness or paralysis of muscles while sensations remain intact. Here is a list of causes of this type of polyneuropathy.
I. Guillain-Barre Syndrome (GBS)
II. Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)
III. Multifocal Motor Neuropathy (MMN)
IV. Porphyria
V. Lead
VI. Diphtheria
4. Focal and/or Multifocal Neuropathies:

This kind of neuropathies have no set pattern and can occur in any part of the body any time or can occur in various parts of the body simultaneously. Causes of this kind of neuropathies include:
I. Connective Tissue Diseases
II. Vasculitis
III. Granulomatous Disorders such as Wegener’s Granulomatosis or Sarcoidosis
IV. Malignant Infiltration
V. Nerve Compression such as Peroneal Nerve Compression
VI. Hereditary Neuropathy with Liability to Pressure Palsy (HNLPP)
VII. HIV
VIII. Leprosy
IX. Diabetes Mellitus
X. Fabry’s Disease