Case of Gut Necrosis in Adult-Onset Immunoglobulin A Vasculitis (Henoch-Schönlein Purpura).

Immunoglobulin A vasculitis (IgAV), formerly known as Henoch-Schönlein purpura, is an immune-mediated small vessel vasculitis characterized by palpable purpura, arthralgia, abdominal pain, and renal disease. It is primarily a childhood disease and usually resolves spontaneously with supportive therapy. Treatment of IgAV in adults is controversial with no clearly established guidelines. We report a rare case of IgAV in an adult male who developed gut necrosis and perforation while receiving glucocorticoid therapy for treatment of acute glomerulonephritis. A 44-year-old male was admitted with joint pain, leg swelling, mild abdominal pain, and a diffuse rash. Laboratory values revealed acute kidney injury with significant proteinuria and hematuria. The patient was started on glucocorticoid therapy for suspected IgAV nephritis, which was confirmed by kidney biopsy. Several days later, he complained of worsening abdominal pain. Imaging demonstrated bowel ischemia and perforation requiring multiple abdominal surgeries. The patient was critically ill in the intensive care unit with worsening renal failure requiring dialysis. He was discharged a month later after gradual recovery with stable but moderately impaired kidney function. IgAV is less common in adults; however, the disease is more severe with a higher risk of long-term complications. Adult patients with renal involvement may benefit from glucocorticoid therapy in preventing progression to end-stage renal disease. However, glucocorticoids may mask the symptoms of abdominal complications like gut necrosis and perforation causing delay in diagnosis and treatment. Therefore, vigilance to detect early signs of gut ischemia is imperative when treating an adult case of IgAV nephritis with glucocorticoids.

Molecular Mechanism underlying PRMT1 Dimerization for SAM Binding and Methylase Activity.

Protein arginine methyltransferases (PRMTs) catalyze the posttranslational methylation of arginine, which is important in a range of biological processes, including epigenetic regulation, signal transduction, and cancer progression. Although previous studies of PRMT1 mutants suggest that the dimerization arm and the N-terminal region of PRMT1 are important for activity, the contributions of these regions to the structural architecture of the protein and its catalytic methylation activity remain elusive. Molecular dynamics (MD) simulations performed in this study showed that both the dimerization arm and the N-terminal region undergo conformational changes upon dimerization. Because a correlation was found between the two regions despite their physical distance, an allosteric pathway mechanism was proposed based on a network topological analysis. The mutation of residues along the allosteric pathways markedly reduced the methylation activity of PRMT1, which may be attributable to the destruction of dimer formation and accordingly reduced S-adenosyl-L-methionine (SAM) binding. This study provides the first demonstration of the use of a combination of MD simulations, network topological analysis, and biochemical assays for the exploration of allosteric regulation upon PRMT1 dimerization. These findings illuminate the results of mechanistic studies of PRMT1, which have revealed that dimer formation facilitates SAM binding and catalytic methylation, and provided direction for further allosteric studies of the PRMT family.