CIDP

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a chronic autoimmune disorder of the peripheral nervous system characterized by demyelination, leading to weakness and sensory symptoms. It typically presents with a progressive or relapsing course over at least several weeks and is distinguished from acute inflammatory demyelinating polyneuropathy by its longer duration and often more gradual progression. CIDP can be translationally symmetric and involve proximal and distal muscles, with sensory symptoms such as numbness or tingling and reduced reflexes.

Common clinical features include symmetric weakness of both proximal and distal muscles, sensory loss, and decreased or absent reflexes. Symptoms may progress over months and can remit or relapse. Variants exist, such as multifocal acquired demyelinating sensorimotor neuropathy (MADSAM, or Lewis-Sumner syndrome), which is typically asymmetric and multifocal, and distal acquired demyelinating symmetric neuropathy (DADS), which predominantly affects distal limbs.

The pathophysiology is believed to be autoimmune-mediated, with inflammation targeting peripheral nerve myelin. This results in demyelination, slowed nerve conduction, conduction blocks, and secondary axonal injury in some cases. Nerve biopsy is not routinely required but may show demyelination with onion-bulb formations in chronic disease.

Diagnosis relies on clinical presentation supported by nerve conduction studies showing demyelinating features such as slowed conduction velocity, prolonged distal latencies, and conduction blocks. Cerebrospinal fluid often shows albuminocytologic dissociation (elevated protein with normal cell count). MRI and, occasionally, nerve biopsy can aid diagnosis. Diagnostic criteria such as those from EFNS/PNS are used to standardize classification.

Treatment options include corticosteroids and intravenous immunoglobulin (IVIG) as first-line therapies, with plasma exchange as an alternative. Immunosuppressive agents (e.g., azathioprine, mycophenolate, cyclophosphamide) may be used in refractory cases. Physical and occupational therapy support functional recovery and maintenance. Prognosis varies; many respond to treatment with improved strength, but relapses and residual deficits can occur. CIDP is relatively rare, with incidence estimates around 1 per 100,000 per year.