Heterozygous missense variant of the proteasome subunit β-type 9 causes neonatal-onset autoinflammation and immunodeficiency

Impaired proteasome activity due to genetic variants of certain subunits might lead to proteasome-associated autoinflammatory syndromes (PRAAS). Here we report a de novo heterozygous missense variant of the PSMB9 proteasome subunit gene in two unrelated Japanese infants resulting in amino acid substitution of the glycine (G) by aspartic acid (D) at position 156 of the encoded protein β1i. In addition to PRAAS-like manifestations, these individuals suffer from pulmonary hypertension and immunodeficiency, which are distinct from typical PRAAS symptoms. The missense variant results in impaired immunoproteasome maturation and activity, yet ubiquitin accumulation is hardly detectable in the patients. A mouse model of the heterozygous human genetic variant (Psmb9G156D/+) recapitulates the proteasome defects and the immunodeficiency phenotype of patients. Structurally, PSMB9 G156D interferes with the β-ring-βring interaction of the wild type protein that is necessary for 20S proteasome formation. We propose the term, proteasome-associated autoinflammatory syndrome with immunodeficiency (PRAAS-ID), to indicate a separate category of autoinflammatory diseases, similar to, but distinct from PRAAS, that describes the patients in this study.

Acne Syndromes and Mosaicism

Abnormal mosaicism is the coexistence of cells with at least two genotypes, by the time of birth, in an individual derived from a single zygote, which leads to a disease phenotype. Somatic mosaicism can be further categorized into segmental mosaicism and nonsegmental somatic mosaicism. Acne is a chronic illness characterized by inflammatory changes around and in the pilosebaceous units, commonly due to hormone- and inflammatory signaling-mediated factors. Several systemic disorders, such as congenital adrenal hyperplasia, polycystic ovarian syndrome, and seborrhoea-acne-hirsutism-androgenetic alopecia syndrome have classically been associated with acne. Autoinflammatory syndromes, including PAPA, PASH, PAPASH, PsAPASH, PsaPSASH, PASS, and SAPHO syndromes include acneiform lesions as a key manifestation. Mosaic germline mutations in the FGFR2 gene have been associated with Apert syndrome and nevus comedonicus, two illnesses that are accompanied by acneiform lesions. In this review, we summarize the concept of cutaneous mosaicism and elaborate on acne syndromes, as well as acneiform mosaicism.

Inherited Autoinflammatory Syndromes

Autoinflammation describes a collection of diverse diseases caused by indiscriminate activation of the immune system in an antigen-independent manner. The rapid advancement of genetic diagnostics has allowed for the identification of a wide array of monogenic causes of autoinflammation. While the clinical picture of these syndromes is diverse, it is possible to thematically group many of these diseases under broad categories that provide insight into the mechanisms of disease and therapeutic possibilities. This review covers archetypical examples of inherited autoinflammatory diseases in five major categories: inflammasomopathy, interferonopathy, unfolded protein/cellular stress response, relopathy, and uncategorized. This framework can suggest where future work is needed to identify other genetic causes of autoinflammation, what types of diagnostics need to be developed to care for this patient population, and which options might be considered for novel therapeutic targeting. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Molecular biology of autoinflammatory diseases

The long battle between humans and various physical, chemical, and biological insults that cause cell injury (e.g., products of tissue damage, metabolites, and/or infections) have led to the evolution of various adaptive responses. These responses are triggered by recognition of damage-associated molecular patterns (DAMPs) and/or pathogen-associated molecular patterns (PAMPs), usually by cells of the innate immune system. DAMPs and PAMPs are recognized by pattern recognition receptors (PRRs) expressed by innate immune cells; this recognition triggers inflammation. Autoinflammatory diseases are strongly associated with dysregulation of PRR interactomes, which include inflammasomes, NF-κB-activating signalosomes, type I interferon-inducing signalosomes, and immuno-proteasome; disruptions of regulation of these interactomes leads to inflammasomopathies, relopathies, interferonopathies, and proteasome-associated autoinflammatory syndromes, respectively. In this review, we discuss the currently accepted molecular mechanisms underlying several autoinflammatory diseases.

Autoinflammatory syndromes in neurology: when our first line of defence misbehaves

Autoinflammatory syndromes result in a defective innate immune system. They are characterised by unexplained fever and systemic inflammation involving the skin, muscle, joints, serosa and eyes, along with elevated acute phase reactants. Autoinflammatory syndromes are increasingly recognised as a cause of neurological disease with a diverse range of manifestations. Corticosteroids, colchicine and targeted therapies are effective if started early, and hence the importance of recognising these syndromes. Here, we review the neurological features of specific autoinflammatory syndromes and our approach (as adult neurologists) to their diagnosis.

Case Report: PsAPSASH syndrome: an alternative phenotype of syndromic hidradenitis suppurativa treated with the IL-17A inhibitor secukinumab

Syndromic hidradenitis suppurativa (HS) is a form of symptom constellations, which differs from the familial and genetic form and comprises predominantly osteoarticular manifestations. Many forms include pyoderma gangrenosum and acne (PASH), pyogenic arthritis (PAPASH), spondyloarthritis (PASS) and psoriatic arthritis (PsAPASH) and are categorized in the autoinflammatory syndromes. Anti-TNF-α and anti-IL-1a blockade are between the therapeutic approaches that improve skin symptoms and prevent permanent osteoarticular damage. This case report refers to the successful treatment of a mixed phenotype of the aforementioned symptoms using the IL-17A inhibitor secukinumab after initial treatment with adalimumab. The therapy improved both cutaneous and reported osteoarticular symptoms. Different approaches for these recalcitrant HS syndromes are essential in order to achieve long-term remission for those patients.

Case Report: PsAPSASH syndrome: an alternative phenotype of syndromic hidradenitis suppurativa treated with the IL-17A inhibitor secukinumab

Syndromic hidradenitis suppurativa (HS) is a form of symptom constellations, which differs from the familial and genetic form and comprises predominantly osteoarticular manifestations. Many forms include pyoderma gangrenosum and acne (PASH), pyogenic arthritis (PAPASH), spondyloarthritis (PASS) and psoriatic arthritis (PsaPASH) and are categorized in the autoinflammatory syndromes. anti-TNF-α and anti-IL-1a blockade are between the therapeutic approaches that improve skin symptoms and prevent permanent osteoarticular damage. This case report refers to the successful treatment of a mixed phenotype of the aforementioned symptoms using the IL-17A inhibitor secukinumab after initial treatment with adalimumab. The therapy improved both cutaneous and reported osteoarticular symptoms. Different approaches for these recalcitrant HS syndromes are essential in order to achieve long-term remission for those patients.

Trained Immunity: Reprogramming Innate Immunity in Health and Disease

Traditionally, the innate and adaptive immune systems are differentiated by their specificity and memory capacity. In recent years, however, this paradigm has shifted: Cells of the innate immune system appear to be able to gain memory characteristics after transient stimulation, resulting in an enhanced response upon secondary challenge. This phenomenon has been called trained immunity. Trained immunity is characterized by nonspecific increased responsiveness, mediated via extensive metabolic and epigenetic reprogramming. Trained immunity explains the heterologous effects of vaccines, which result in increased protection against secondary infections. However, in chronic inflammatory conditions, trained immunity can induce maladaptive effects and contribute to hyperinflammation and progression of cardiovascular disease, autoinflammatory syndromes, and neuroinflammation. In this review we summarize the current state of the field of trained immunity, its mechanisms, and its roles in both health and disease.