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PSMB8 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

PSMB8 gene

The PSMB8 gene provides instructions for a subunit of the immunoproteasome, a complex essential for regulating immune responses and maintaining protein homeostasis.

Normal Function

The PSMB8 gene provides instructions for making one subunit of immunoproteasomes. These are specialized complexes that recognize and break down (degrade) unneeded, excess, or abnormal proteins within cells. While regular proteasomes are found in many cells, immunoproteasomes are located primarily in immune system cells.

Immunoproteasomes help the immune system distinguish the body's own proteins from those of foreign invaders like viruses and bacteria. They are also involved in fundamental cell activities, including protein homeostasis, cell growth, division, differentiation, and gene activity. The subunit produced by PSMB8 may also play a role in the maturation of fat cells (adipocytes).

Health Conditions Related to Genetic Changes

Nakajo-Nishimura syndrome

Mutations in the PSMB8 gene, such as Gly201Val (G201V), cause Nakajo-Nishimura syndrome. This mutation reduces protein production, impairing immunoproteasome assembly and causing the immune system to malfunction. This leads to abnormal inflammation that damages tissues, resulting in:

  • Red, swollen skin lumps (nodular erythema)
  • Recurrent fevers
  • Joint problems
  • Enlarged liver and spleen (hepatosplenomegaly)
  • Muscle weakness and wasting
  • Loss of fatty tissue (lipodystrophy)

Other disorders

Mutations in the PSMB8 gene are also linked to two other conditions with overlapping symptoms:

  • JMP syndrome (joint contractures, muscular atrophy, microcytic anemia, and panniculitis-induced lipodystrophy)
  • CANDLE syndrome (chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature)

These conditions are characterized by skin abnormalities and lipodystrophy. Some researchers believe these syndromes may represent different forms of a single condition, as they share similar genetic mutations, such as Thr75Met (T75M) and Cys135Ter (C135X), which significantly reduce protein production.

Other Names for This Gene

  • ALDD
  • beta5i
  • D6S216
  • D6S216E
  • JMP
  • large multifunctional peptidase 7
  • LMP7
  • low molecular mass protein 7
  • low molecular weight protein 7
  • macropain subunit C13
  • multicatalytic endopeptidase complex subunit C13
  • NKJO
  • protease component C13
  • proteasome (prosome, macropain) subunit, beta type, 8
  • proteasome catalytic subunit 3i
  • proteasome subunit beta 5i
  • proteasome subunit beta type-8
  • proteasome subunit Y2
  • proteasome-related gene 7
  • PSB8_HUMAN
  • PSMB5i
  • really interesting new gene 10 protein
  • RING10

Frequently Asked Questions

While the underlying genetic defect causes chronic inflammation, certain factors can exacerbate symptoms. Patients often report that physical stress, infections, or extreme temperatures can trigger flares of fever and skin lesions. Because the immune system is dysregulated, even minor viral or bacterial infections can lead to disproportionate inflammatory responses. Keeping a symptom diary to track potential triggers, such as new medications, dietary changes, or environmental stressors, can help patients and caregivers identify patterns and work with their medical team to develop a proactive management plan for flare-ups.
The prognosis varies significantly among individuals, but these conditions are chronic and require lifelong management. Early and consistent treatment with anti-inflammatory medications, such as IL-1 inhibitors, can help control fever and skin symptoms, potentially reducing the risk of long-term organ damage. However, complications such as chronic liver inflammation, joint contractures, and severe muscle wasting can develop over time. Regular monitoring of liver function, joint mobility, and nutritional status is critical. While there is no cure for the genetic mutation, early intervention and multidisciplinary care can improve quality of life and slow the progression of tissue damage.
Diagnosis typically begins with a clinical evaluation by a geneticist or immunologist who looks for the hallmark symptoms such as nodular erythema, recurrent fevers, and lipodystrophy. Confirmation requires genetic testing, specifically sequencing of the PSMB8 gene to identify pathogenic variants like G201V. Because the symptoms overlap with other autoinflammatory disorders, clinicians may also perform inflammatory marker blood tests and skin biopsies to rule out other conditions before genetic results are available. It is important to note that standard blood panels do not detect the genetic cause, so targeted genetic sequencing is the definitive diagnostic step.
Most PSMB8-related syndromes, including Nakajo-Nishimura, CANDLE, and JMP syndromes, are inherited in an autosomal recessive pattern. This means that a child must inherit two mutated copies of the gene, one from each parent, to develop the condition. Parents who are carriers typically do not show symptoms. If a couple has one affected child, there is a 25% chance with each subsequent pregnancy that the child will be affected, a 50% chance the child will be a carrier, and a 25% chance the child will not carry the mutation. Genetic counseling is strongly recommended for family planning and to discuss options such as prenatal testing or preimplantation genetic diagnosis.
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.

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