ABSTRACT
A 55-year-old man undergoing chemotherapy for recurrent multiple myeloma presented with a 2-day history of bilateral lower leg rash with pain and oedema. On examination, there were numerous non-palpable retiform pruritic patches over both lower legs. Skin pnch biopsy demonstrated a diffuse interstitial neutrophilic infiltrate with necrosis. Peripheral blood and skin tissue cultures both isolated Citrobacterfreundii, consistent with a rare form of ecthyma gangrenosum. The patient responded with appropriate antibiotic therapy and removal of medical port. He made a full recovery from this infectious complication of his underlying immunosuppression.
Subject(s)
Anti-Bacterial Agents/administration & dosage , Citrobacter freundii/drug effects , Ecthyma/microbiology , Enterobacteriaceae Infections/microbiology , Lower Extremity/microbiology , Multiple Myeloma/drug therapy , Thienamycins/administration & dosage , Debridement , Ecthyma/drug therapy , Ecthyma/immunology , Enterobacteriaceae Infections/drug therapy , Humans , Immunocompromised Host , Male , Meropenem , Middle Aged , Multiple Myeloma/immunology , Rare Diseases , Treatment OutcomeABSTRACT
The rs2004640 single nucleotide polymorphism and the CGGGG copy-number variant (rs77571059) are promoter polymorphisms within interferon regulatory factor 5 (IRF5). They have been implicated as susceptibility factors for several autoimmune diseases. IRF5 uses alternative promoter splicing, where any of 4 first exons begin the mRNA. The CGGGG indel is in exon 1A's promoter; the rs2004640 allele creates a splicing recognition site, enabling usage of exon 1B. This study aimed at characterizing alterations in IRF5 mRNA due to these polymorphisms. Cells with risk polymorphisms exhibited ~2-fold higher levels of IRF5 mRNA and protein, but demonstrated no change in mRNA stability. Quantitative PCR demonstrated decreased usage of exons 1C and 1D in cell lines with the risk polymorphisms. RNA folding analysis revealed a hairpin in exon 1B; mutational analysis showed that the hairpin shape decreased translation 5-fold. Although translation of mRNA that uses exon 1B is low due to a hairpin, increased IRF5 mRNA levels in individuals with the rs2004640 risk allele lead to higher overall protein expression. In addition, several new splice variants of IRF5 were sequenced. IRF5's promoter polymorphisms alter first exon usage and increase transcription levels. High levels of IRF5 may bias the immune system toward autoimmunity.
