Oncostatin M receptor deficiency as a novel candidate genetic cause of autosomal recessive hyper-IgE syndrome

Hyper-IgE syndrome (HIES) is characterized by elevated serum IgE levels, eczema, and recurrent skin and pulmonary infections, classically caused by autosomal dominant (AD) STAT3 loss-of-function variants. Here we describe a patient presenting with elevated IgE levels, atopic eczema, chronic pulmonary aspergillosis, and bone fractures, homozygous for a rare missense variant in the oncostatin M receptor (<i>OSMR</i>) gene. We demonstrate that the patient OSMR V436D variant is deleterious and leads to decreased OSMR surface expression and impaired OSM-induced STAT3 phosphorylation. Blood profiling showed elevated IgE-expressing plasmablasts and peripheral T follicular helper cells and atypical memory B cells. A germinal center model revealed a B cell-extrinsic defect in concordance with a largely fibroblast-confined phenotype. Finally, reconstitution of patient fibroblasts led to functional complementation of the cellular phenotype. We propose OSMR deficiency as a novel genetic etiology of AR-HIES, resembling the clinical and immunological phenotype of STAT3 AD-HIES, but mediating its phenotypic profile mainly in the stromal rather than hematopoietic compartment.