A de novo dominant-negative variant is associated with OTULIN-related autoinflammatory syndrome.

OTULIN-related autoinflammatory syndrome (ORAS), a severe autoinflammatory disease, is caused by biallelic pathogenic variants of OTULIN, a linear ubiquitin-specific deubiquitinating enzyme. Loss of OTULIN attenuates linear ubiquitination by inhibiting the linear ubiquitin chain assembly complex (LUBAC). Here, we report a patient who harbors two rare heterozygous variants of OTULIN (p.P152L and p.R306Q). We demonstrated accumulation of linear ubiquitin chains upon TNF stimulation and augmented TNF-induced cell death in mesenchymal stem cells differentiated from patient-derived iPS cells, which confirms that the patient has ORAS. However, although the de novo p.R306Q variant exhibits attenuated deubiquitination activity without reducing the amount of OTULIN, the deubiquitination activity of the p.P152L variant inherited from the mother was equivalent to that of the wild-type. Patient-derived MSCs in which the p.P152L variant was replaced with wild-type also exhibited augmented TNF-induced cell death and accumulation of linear chains. The finding that ORAS can be caused by a dominant-negative p.R306Q variant of OTULIN furthers our understanding of disease pathogenesis.

Clinical and histological features of histiocytoid Sweet syndrome associated with VEXAS syndrome.

BACKGROUND: VEXAS (Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome is caused by acquired somatic mutations in UBA1. Sweet-syndrome-like skin disorders [and especially histiocytoid Sweet syndrome (HSS)] may be associated with VEXAS syndrome. OBJECTIVES: To characterize the clinical and histopathological features of HSS in patients with VEXAS syndrome. METHODS: Skin biopsies with a histological diagnosis of HSS at Rennes University Medical Center (Rennes, France) between October 2011 and January 2022 were reviewed in this study. Sanger sequencing and digital polymerase chain reaction were used to screen skin, blood and bone marrow samples for UBA1 variants, and thus classify patients as having VEXAS syndrome or not. We evaluated the clinical, histological and molecular (UBA1) characteristics of patients with or without VEXAS syndrome. RESULTS: We compared 15 skin biopsies from 7 patients found to have VEXAS syndrome and 19 skin biopsies from 15 patients without VEXAS syndrome. Persistent C-reactive protein elevation, macrocytosis, anaemia and haematological malignancies were more prevalent in patients with VEXAS syndrome [6/7 (86%), 6/7 (86%), 7/7 (100%) and 6/7 (86%), respectively] than in patients without [5/14 (36%), 6/15 (40%), 8/15 (53%) and 8/15 (53%), respectively]. These features sometimes appeared after the first skin manifestations, and a UBA1 mutation was found in the skin of five patients with VEXAS syndrome. Dermal infiltration by reniform histiocytoid cells (myeloperoxidase-positive and/or CD163-positive) and a periadnexal distribution were more frequently observed in VEXAS syndrome biopsies [15/15 (100%) and 3/15 (20%), respectively, vs. 11/19 (58%) and 0/19 (0%) in non-VEXAS syndrome biopsies, respectively]. CONCLUSIONS: Our findings might help pathologists to consider a diagnosis of VEXAS syndrome and to initiate early genetic testing.

Enfermedades autoinflamatorias / Autoinflammatory diseases

Las enfermedades autoinflamatorias monogénicas son desórdenes raros que resultan en defectos del sistema inmune innato, originando excesiva respuesta a señales de peligro, activación espontánea de vías inflamatorias o pérdida de reguladores inhibitorios. En los últimos 15 años un creciente número de enfermedades inflamatorias monogénicas han sido descriptas y sus respectivos genes responsables identificados. Las proteínas codificadas por estos genes están involucradas en las vías regulatorias de la inflamación y están expresadas fundamentalmente en las células del sistema inmune innato. Si bien un grupo de pacientes exhibe inflamación sistémica episódica (fiebres periódicas), estos desórdenes están mediados por una continua sobreproducción y liberación de mediadores pro-inflamatorios -especialmente la interleucina 1beta- y su conceptualización como enfermedades autoinflamatorias es preferible por sobre la de fiebres periódicas. Las enfermedades más frecuentes son fiebre mediterránea familiar (FMF), TRAPS, deficiencia de mevalonatocinasa/síndrome de hiper IgD (MKD/HIDS) y los síndromes periódicos asociados a criopirina (CAPS). Sus características clínicas frecuentemente incluyen fiebre, erupciones cutáneas, compromiso de serosas y reactantes de fase aguda. Los autoanticuerpos están usualmente ausentes pero pueden observarse en ciertos síndromes. El diagnóstico es clínico y se basa en las características fenotípicas. El diagnóstico genético es muy importante pero debe ser realizado de manera juiciosa e interpretado con cautela. El tratamiento con agentes biológicos que bloquean citocinas pro-inflamatorias, particularmente IL-1, ha demostrado ser efectivo en muchos pacientes. Sin embargo, en otros tantos casos no se descubren anormalidades genéticas y el tratamiento es subóptimo, planteando la posibilidad de mutaciones patogénicas en genes y vías aún no explorados.

The monogenic autoinflammatory diseases are rare, genetic disorders resulting in constitutive innate immune defects leading to excessive response to danger signals, spontaneous activation of inflammatory mediators or loss of inhibitory regulators. During the past 15 years, a growing number of monogenic inflammatory diseases have been described and their respective responsible genes identified. The proteins encoded by these genes are involved in the regulatory pathways of inflammation and are mostly expressed in cells of the innate immune system. Although a group of patients exhibit episodic systemic inflammation (periodic fevers), these disorders are mediated by continuous overproduction and release of pro-inflammatory mediators, notably IL-1β, and are best considered as autoinflammatory diseases rather than periodic fevers. The most common autoinflammatory diseases are familial Mediterranean fever (FMF), TNF receptor-associated periodic syndrome (TRAPS), mevalonate kinase deficiency/hyperimmunoglobulin D syndrome (MKD/HIDS) and the cryopyrin-associated periodic syndromes (CAPS). Clinical features often include fever, cutaneous rash, serosal involvement and acute phase reactants. Autoantibodies are usually absent but may accompany certain syndromes. Diagnosis remains clinical and is based on the different phenotypic features. Genetic diagnosis is of utmost importance, but must be performed judiciously and interpreted cautiously. Treatment with biologic agents that block proinflammatory cytokines, particularly IL-1, has proved to be dramatically effective in many patients. Still, in many cases of autoinflammation no genetic abnormalities are detected and treatment remains suboptimal, raising the question of novel pathogenic mutations in unexplored genes and pathways.