Poly-ostotic Langerhans Cell Histiocytosis (LCH) can be difficult to distinguish clinically and histologically from disseminated infection in manifesting specific subtypes of Mendelian Susceptibility to Mycobacterial Disease (MSMD). In MSMD-patients, dominant negative germline mutations in the IFN-gamma R1 gene, in particular in exon 6, lead to autosomal dominant IFN-gamma receptor 1 deficiency (ADIFNGR1) and can mimic LCH. We hypothesized that similar defects might underlie the pathogenesis of LCH.
IFN-gamma R1 expression was immunohistochemically determined at disease onset in biopsies from 11 LCH-patients and four ADIFNGR1-patients. IFN-gamma R1 function was analyzed in 18 LCH-patients and 13 healthy controls by assessing the IFN-gamma-induced upregulation of Fc-gamma-receptor I (Fc gamma RI) expression on monocytes. Pro-inflammatory cytokine production was measured after stimulation of whole blood with LPS and IFN-gamma. Exon 6 of the IFN-gamma R1 gene was sequenced in 67 LCH-patients to determine whether mutations were present.
IFN-gamma R1 expression was high in three LCH-affected biopsies, similar to ADIFNGR1-affected biopsies, but varied from negative to moderate in eight other LCH-affected biopsies. No functional differences in IFN-gamma signaling were detected between LCH-patients with active or non-active disease and healthy controls. No germline mutations in exon 6 of the IFN-gamma R1 gene were detected in any of the 67 LCH-patients.
In contrast to ADIFNGR1-patients, IFN-gamma signaling is fully functional in LCH-patients. Either performed before, during or after treatment, these non-invasive functional assays can distinguish LCH-patients from ADIFNGR1-patients and thereby facilitate correct therapy regimens for patients with recurrent osteolytic lesions.
- Langerhans cell histiocytosis
- mendelian susceptibility to mycobacterial disease
- diagnostic approaches
- interferon-gamma receptor-1
- autosomal dominant IFN-gamma R1 deficiency
- GAMMA RECEPTOR DEFICIENCY
- CYTOKINE PROFILES