Mitochondrial stress engages E2F1 apoptotic signaling to cause deafness.

Mitochondrial dysfunction causes poorly understood tissue-specific pathology stemming from primary defects in respiration, coupled with altered reactive oxygen species (ROS), metabolic signaling, and apoptosis. The A1555G mtDNA mutation that causes maternally inherited deafness disrupts mitochondrial ribosome function, in part, via increased methylation of the mitochondrial 12S rRNA by the methyltransferase mtTFB1. In patient-derived A1555G cells, we show that 12S rRNA hypermethylation causes ROS-dependent activation of AMP kinase and the proapoptotic nuclear transcription factor E2F1. This retrograde mitochondrial-stress relay is operative in vivo, as transgenic-mtTFB1 mice exhibit enhanced 12S rRNA methylation in multiple tissues, increased E2F1 and apoptosis in the stria vascularis and spiral ganglion neurons of the inner ear, and progressive E2F1-dependent hearing loss. This mouse mitochondrial disease model provides a robust platform for deciphering the complex tissue specificity of human mitochondrial-based disorders, as well as the precise pathogenic mechanism of maternally inherited deafness and its exacerbation by environmental factors.

Use of intravenous immunoglobulin to treat chronic bilateral otomastoiditis in the setting of rituximab induced hypogammaglobulinemia.

The temporal bone may be affected by a variety of systemic pathology because the disease nature, location, and extent determine the symptoms. Middle ear and mastoid infections may be the initial clinical manifestation of autoimmune and acquired immunodeficiency disorders. Rituximab, an anti-CD20 chimeric antibody, has become increasingly popular as a therapeutic agent for patients with a wide range of autoimmune disorders refractory to standard treatments. Normal levels of immunoglobulin levels are usually maintained during and after rituximab therapy, and clinical trials to date have shown no statistically significant increase of serious infections among patients with autoimmune diseases being treated with rituximab (Cohen SB, Emery P, Greenwald MW, Dougados M, Furie RA, Genovese MC, et al, for the REFLEX Trial Group. Rituximab for rheumatoid arthritis refractory to anti-tumor necrosis factor therapy: results of a multicenter, randomized, double-blind, placebo-controlled, phase III trial evaluating primary efficacy and safety at 24 weeks. Arthritis Rheum. 2006;54:2793-2806. Edwards JC, Szczepanski L, Szechinski J, Filipowicz-Sosnowska A, Emery P, Close DR, et al. Efficacy of B-cell-targeted therapy with rituximab in patients with rheumatoid arthritis. N Engl J Med. 2004;350:2572-2581). However, there have been several reports of opportunistic infections associated with rituximab (Kelesidis T, Daikos G, et al. Does rituximab increase the incidence of infectious complications? A narrative review. Int J Infect Dis 2011;15:e2-e16. Teichmann LL, Woenckhaus M, Vogel C, et al. Fatal Pneumocystis pneumonia following rituximab administration for rheumatoid arthritis. Rheumatology 2008;47:1256-1257), as well as cases of it accelerating the presentation of hypogammaglobulinemia (Diwakar L, Gorrie S, et al. Does rituximab aggravate pre-existing hypogammaglobulinaemia? J Clin Pathol 2010;63:275-277). Humoral immune defects can cause persistent acute and serous otitis media, with the development of chronic suppurative otitis media refractory to medical and surgical therapy (Sasaki CT, Askenase P, Dwyer J, et al. Chronic ear infection in the immunodeficient patient. Arch Otolaryngol 1981;107:82). Here, we describe the first presentation, diagnostic workup, and treatment with intravenous immunoglobulin of chronic bilateral otomastoiditis in the setting of rituximab-induced hypogammaglobulinemia.

Pediatric shunt malfunction without ventricular dilatation.

BACKGROUND/PURPOSE: Symptomatic ventriculoperitoneal shunt (VPS) malfunction can occur without progressive ventricular dilatation on imaging studies. A review of VPS revisions performed during an 18-month period was conducted to better characterize this cohort. The incidence of VPS malfunction without ventricular dilatation and the clinical features that may predispose to its occurrence have not been previously described. METHODS: A retrospective review was conducted of all patients under the age of 18 who underwent VPS revision due to shunt malfunction from June 2001 to December 2002. The incidence of various factors that might correlate with the development of low compliance ventricles was examined. RESULTS: One hundred and seventy-seven patients underwent a total of 287 VPS revisions during the study period; 16 patients (9%) had signs of raised intracranial pressure and showed no radiographic evidence of progressive ventricular dilatation. History of prior shunt-related ventriculitis positively correlated with the development of low compliance ventricles (Fisher's exact test, p = 0.043). CONCLUSION: Nine percent of pediatric patients with symptomatic VPS malfunctions lack radiographic evidence of progressive ventricular dilatation on imaging studies. Patients with prior shunt infections are particularly at risk, necessitating increased vigilance when clinical signs and symptoms are apparent.