VGKC PROFILE, SERUM

VGKC Profile, Serum

What it is

The VGKC (Voltage-Gated Potassium Channel) Profile, Serum test measures autoantibodies directed against proteins of the VGKC complex in the blood. The profile usually includes antibodies against LGI1 (Leucine-rich Glioma-Inactivated 1) and CASPR2 (Contactin-Associated Protein-like 2), which are the most clinically relevant markers. These antibodies are associated with autoimmune neurological conditions affecting the central and peripheral nervous system.

Uses

This test is used to support the diagnosis of autoimmune encephalitis, neuromyotonia, Morvan’s syndrome, and related VGKC-complex disorders. It helps differentiate between neurological symptoms caused by immune-mediated mechanisms versus other causes, and it guides treatment decisions such as the use of immunotherapy.

Symptoms That May Lead to the Test

Doctors may recommend this test for patients with unexplained seizures, memory loss, personality or behavioral changes, psychiatric symptoms, abnormal movements, neuropathic pain, persistent muscle twitching, or signs of autonomic dysfunction (e.g., abnormal sweating, blood pressure instability). It may also be ordered when paraneoplastic autoimmune syndromes are suspected.

Abnormal Results

Positive LGI1 Antibodies: Strongly linked to limbic encephalitis, seizures, cognitive decline, and hyponatremia. Patients often respond well to steroids or immunotherapy.

Positive CASPR2 Antibodies: Associated with neuromyotonia, Morvan’s syndrome, peripheral nerve hyperexcitability, and sometimes encephalitis.

Negative Profile: Indicates no detectable VGKC-related antibodies, though other autoimmune or paraneoplastic antibody panels may still be needed.

Risks

The test requires a routine blood draw, which carries minimal risks such as mild bruising, pain, or dizziness. These side effects are short-lived and rarely serious.