Neutrophilic dermatosis associated with an NFKB2 mutation

Type-Specific Impacts of Protein Defects in Pathogenic NFKB2 Variants: Novel Clinical Findings From 138 Patients

BACKGROUND

The noncanonical NF-κB2 (nuclear factor kappa B subunit 2) pathway is integral in regulating immunologic responses, supervising immune function, development, and homeostasis. NFKB2 encodes the cytoplasmic precursor p100, which undergoes processing of its inhibitory C-terminal half to generate p52. Impeding C-terminal defects are well established to cause primary immunodeficiency disorder. In contrast, the mechanism of truncating N-terminal defects remains obscure.

OBJECTIVE

We characterized clinical phenotypes associated with 3 distinct protein-defect types: (1) early truncations: typically occurring N-terminal relative to the nuclear localization sequence and affecting the Rel homology domain, predicting p100 expression to be halved and subsequent p52 generation by processing to be diminished; (2) central truncations: mainly affecting the ARD and predicting immediate expression of p52-like proteins and a 50% reduction of p100; and (3) C-terminal phosphorylation-/ubiquitination domain defects: causing expression of nonprocessable p100 with retained IκB-like activity and subsequently reducing generation of p52.

METHODS

We performed literature research on PubMed, Clinvar, and Human Gene Mutation Database collecting clinical and immunologic data on NFKB2 patients, focusing on comparing protein-defect-specific impacts.

RESULTS

The highest prevalence of early-onset primary immunodeficiency disorder and antibody deficiency occurred in the CTD-defect group. In addition, endocrinological abnormalities and T-cell-mediated autoimmunity were common and frequently required immunosuppression. An extensive immunologic workup revealed patients with C-terminal defects to have pan-hypogammaglobulinemia and reduced specific antibody responses and markedly impaired B-cell differentiation, but normal to elevated T-cell counts. In contrast, pathogenic NFKB2 variants causing central or early-truncating protein defects were only partially penetrant, with ameliorated symptoms and diminished T-cell-mediated autoimmunity.

CONCLUSIONS

Our work defines a clear genotype-phenotype correlation for NFKB2 mutations.

A novel NFKB1 variant in a Japanese pedigree with common variable immunodeficiency

Recently, heterozygous loss-of-function NFKB1 variants were identified as the primary cause of common variable immunodeficiency (CVID) in the European population. However, pathogenic NFKB1 variants have never been reported in the Japanese population. We present a 29-year-old Japanese woman with CVID. A novel variant, c.136 C > T, p.(Gln46*), was identified in NFKB1. Her mother and daughter carried the same variant, demonstrating the first Japanese pedigree with an NFKB1 pathogenic variant.

Inflammation and Neutrophil Oxidative Burst in a Family with NFKB1 p.R157X LOF and Sterile Necrotizing Fasciitis

Loss-of-function (LOF) mutations in NFKB1, coding for p105, may cause common variable immunodeficiency due to dysregulation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κΒ) pathway. Monoallelic LOF variants of NFKB1 can predispose to uncontrolled inflammation including sterile necrotizing fasciitis or pyoderma gangrenosum. In this study, we explored the impact of a heterozygous NFKB1 c.C936T/p.R157X LOF variant on immunity in sterile fasciitis patients and their family members. The p50 or p105 protein levels were reduced in all variant carriers. Interleukin-1β (IL-1β) and interleukin-8 (IL-8) levels were elevated in vitro, potentially contributing to the very high neutrophil counts observed during fasciitis episodes. Phosphorylation of p65/RelA was reduced in p.R157X neutrophils suggesting defective activation of canonical NF-κB. Oxidative burst after NF-κB-independent phorbol 12-myristate 13-acetate (PMA) stimulation was similar in both p.R157X and control neutrophils. Comparable amounts of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex subunits were found in p.R157X and control neutrophils. However, a compromised oxidative burst was observed in p.R157X neutrophils following activation of NF-κB-dependent mechanisms following stimulation of toll-like receptor 2 (TLR2) and Dectin-1. Neutrophil extracellular trap formation was not affected by p.R157X. In summary, the NFKB1 c.C936T/p.R157X LOF variant has an impact on inflammation and neutrophil function and may play a role in the pathogenesis of sterile necrotizing fasciitis.

Disseminated Coccidioidomycosis as the First Presentation of a C-Terminal NFKB2 Pathogenic Variant: A Case Report and Review of the Literature

INTRODUCTION

Although most cases of coccidioidomycosis are subclinical or self-limited respiratory disease, 1% lead to extrathoracic dissemination and become fatal, especially in patients with an associated immunodeficiency. Up to 30%-50% of patients with defects in cell-mediated immunity, those with AIDS and recipients of solid-organ transplants, may develop disseminated coccidioidomycosis (DC). Within the primary immunodeficiencies, an uncommon group is caused by C-terminal NFKB2 pathogenic variants.

MATERIALS AND METHODS

We performed a literature search of core databases. Written informed consent for the study and for publication was obtained.

CASE PRESENTATION

A 7-year-old Mexican girl, eldest of 3 sisters, no relevant family history, and a history of recurrent upper respiratory infections and alopecia totalis was admitted with DC involving pulmonary, soft tissue, skin, bone and joint compromise. The immunodeficiency assessment showed low IgM and NK cells. We found an NFKB2 de novo heterozygous nonsense mutation of c.2611C>T (p.Gln871*). She was treated with liposomal amphotericin B and itraconazole with surgical debridement. The clinical phenotype of this primary immunodeficiency is characterized by antibody deficiency and associated broncho-pulmonary predisposition to infection, but moreover also opportunistic infections and autoimmunity, most recognizable alopecia and adrenocorticotropic hormone-deficiency. After 1 year of her discharge, she continues under surveillance with antifungal therapy with itraconazole and replacement intravenous immunoglobulin until today.

CONCLUSION

This is the first case report of DC in a patient with an NFKB2 pathogenic variant and it illustrates the importance of screening for primary immunodeficiencies in patients with disseminated fungal infections.