HomeGeneticsGeneCSTB gene
Back to Gene
CSTB gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CSTB gene

The CSTB gene provides instructions for producing cystatin B, a protein that protects cells and regulates nervous system function.

Normal Function

The CSTB gene provides instructions for making a protein called cystatin B. This protein inhibits enzymes called cathepsins, which break down proteins within cellular compartments called lysosomes. Cystatin B protects the cell's proteins from cathepsins that may leak out of lysosomes.

Cystatin B is also believed to:

  • Play a role in the development, movement, and communication of nerve cells.
  • Control the nervous system's immune response (inflammation).
  • Protect cells from damage caused by oxidative stress.

Health Conditions Related to Genetic Changes

Progressive myoclonic epilepsy type 1

Most variants in the CSTB gene cause progressive myoclonic epilepsy type 1, a rare inherited form of epilepsy. This condition is often caused by a dodecamer repeat expansion—a specific DNA sequence that is normally repeated two or three times but is repeated more than 30 times in affected individuals.

The expanded repeat interferes with the production of the cystatin B protein, leaving levels at only 5 to 10 percent of normal. While the exact mechanism is unknown, this reduction is believed to cause the signs and symptoms of the disorder.

Some individuals may carry one copy of the repeat expansion and one copy of a different type of CSTB variant, such as an amino acid substitution or a variant that leads to a shortened, nonfunctional protein. These individuals may experience more severe symptoms.

Other Disorders

In rare cases, individuals may have two variants that result in no cystatin B production at all. These individuals exhibit more severe symptoms, including:

  • Small head size (microcephaly).
  • Severe developmental delays.
  • Abnormal movements (dyskinesia).
  • Seizures.
  • Encephalopathy (abnormal brain function).

Other Names for This Gene

  • CPI-B
  • CST6
  • Cystatin B (stefin B)
  • EPM1
  • EPM1A
  • PME
  • Stefin B
  • STFB
  • ULD

Frequently Asked Questions

The expansion is identified by specialized PCR‑based assays (e.g., repeat‑primed PCR) or Southern blot analysis that can size the number of repeats. Standard sequencing may miss large expansions, so a targeted repeat‑expansion test is required when progressive myoclonic epilepsy is suspected.
Patients typically experience myoclonic jerks, generalized tonic‑clonic seizures, and sometimes absence seizures. First‑line antiepileptic drugs include valproate, levetiracetam, and clonazepam; however, many patients require combination therapy. Sodium channel blockers (e.g., carbamazepine) are usually avoided because they can worsen myoclonus.
These children often present with early‑onset microcephaly, profound developmental delay, and refractory epilepsy, leading to a poorer prognosis and higher mortality risk. Early intervention with multidisciplinary teams—neurology, developmental pediatrics, physical/occupational therapy, and nutritional support—is essential. Seizure control, respiratory monitoring, and educational accommodations improve quality of life, but long‑term outcomes remain guarded.
Yes. Adequate sleep, avoidance of photosensitive triggers (flashing lights), and stress reduction can lessen seizure burden. Medications such as clonazepam, piracetam, or perampanel have shown benefit for myoclonus, and a ketogenic diet has helped some refractory cases, though evidence is limited.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

kontakt@hittavard.se

Ⓒ 2024. Alla rättigheter förbehålls av juxt ab

Sök
Om ossVillkor och policyVanliga frågorKontakta oss