Autoinflammatory disorders

Gene: PSMB8

Green List (high evidence)

Comment on mode of inheritance: There is sufficient evidence available (>10 unrelated families and functional work) for the association of monoallelic PSMB8 variants with proteasome-associated autoinflammatory syndrome and immunodeficiency.

Hence, the MOI should be updated to 'BOTH monoallelic and biallelic, autosomal or pseudoautosomal' in the next GMS update.

Created: 13 Aug 2026, 2:19 p.m. | Last Modified: 13 Aug 2026, 2:19 p.m.

Panel Version: 3.20

There is already sufficient evidence available for the association of biallelic variants in this gene with a relevant phenotype - associated with MIM #256040 in OMIM and with PSMB8-related Nakajo syndrome (with 'definitive' rating on the DD panel) in Gene2Phenotype (records last accessed 13 August 2026).

PMID:41253591 (2026) reported the identification of a novel de novo heterozygous PSMB8 variant, p.G209R (c.625G>A/C), identified in 8 unrelated patients (6/8 de novo, 2/8 assumed de novo) presenting with a chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperature/ proteasome-associated autoinflammatory syndrome (CANDLE/ PRAAS) phenotype featuring neonatal-onset systemic inflammation, panniculitis, lipodystrophy, cytopenias (anaemia 8/8, lymphopenia and hypogammaglobulinemia 7/8), recurrent viral/bacterial/fungal infections, and porto-sinusoidal vascular liver disease with nodular regenerative hyperplasia—phenotypically broader and more severe than biallelic PSMB8-CANDLE.

Structural modelling, transfection, and knockout cell studies showed that the PSMB8 p.G209R variant sterically disrupts the β5i–β4 (PSMB2) interface, arresting propeptide processing and 20S maturation in ~75% of assembling immunoproteasomes, directly demonstrating a dominant-negative mechanism rather than simple haploinsufficiency.

PMID:42167218 (2026) reported the identification of five distinct monoallelic missense variants in PSMB8 gene in seven patients from five unrelated families with proteasome-associated autoinflammatory syndromes with immunodeficiency (PRAAS-ID). Four of these variants were inherited de novo in the respective families (although patient I7 inherited from mother (I6), for whom it is de novo), while it is inherited from their mother and mosaic (3%) in one family (patients I2/ I3). These patients presented with neonatal-onset immunodeficiency characterized by recurrent infections, B cell lymphopenia, and hypogammaglobulinemia requiring immunoglobulin replacement. Inflammatory manifestations of variable severity included enteropathy, hepatitis, myositis, and inflammatory lung disease.

Functional studies showed that monoallelic PSMB8 variants impair immunoproteasome assembly, causing ~50% loss of mature IP complexes and reduced IP-specific activity while unincorporated mutant subunits accumulate as a stalled, chaperone-bound ~440-kDa assembly intermediate, rather than simply being degraded. This structural disruption destabilizing key PSMB8-PSMB2/PSMB3 interfaces supports a dominant-negative mechanism that reduces functional immunoproteasome output and drives the combined immunodeficiency and autoinflammation seen in PRAAS-ID.

Monoallelic variants are not yet associated with any phenotypes in OMIM, Gene2Phenotype or ClinGen (last accessed 13 August 2026).

Created: 13 Aug 2026, 2:18 p.m. | Last Modified: 13 Aug 2026, 2:18 p.m.

Panel Version: 3.17

Mode of inheritance
BOTH monoallelic and biallelic, autosomal or pseudoautosomal

Phenotypes
Proteasome-associated autoinflammatory syndrome 1 and digenic forms, OMIM:256040; proteasome-associated autoinflammatory syndrome 1, MONDO:0054698; Immunodeficiency, HP:0002721

Publications

• 41253591
• 42167218

Mode of pathogenicity
Other

Green List (high evidence)

This gene has been added to the panel on the recommendation of the NHS Genomic Medicine Service and should be rated green.

Created: 16 Feb 2022, 11:44 a.m. | Last Modified: 16 Feb 2022, 11:44 a.m.

Panel Version: 0.36