Validation of a New Web Application for Identification of Fungi by Use of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry.

Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry has emerged as a reliable technique to identify molds involved in human diseases, including dermatophytes, provided that exhaustive reference databases are available. This study assessed an online identification application based on original algorithms and an extensive in-house reference database comprising 11,851 spectra (938 fungal species and 246 fungal genera). Validation criteria were established using an initial panel of 422 molds, including dermatophytes, previously identified via DNA sequencing (126 species). The application was further assessed using a separate panel of 501 cultured clinical isolates (88 mold taxa including dermatophytes) derived from five hospital laboratories. A total of 438 (87.35%) isolates were correctly identified at the species level, while 26 (5.22%) were assigned to the correct genus but the wrong species and 37 (7.43%) were not identified, since the defined threshold of 20 was not reached. The use of the Bruker Daltonics database included in the MALDI Biotyper software resulted in a much higher rate of unidentified isolates (39.76 and 74.30% using the score thresholds 1.7 and 2.0, respectively). Moreover, the identification delay of the online application remained compatible with real-time online queries (0.15 s per spectrum), and the application was faster than identifications using the MALDI Biotyper software. This is the first study to assess an online identification system based on MALDI-TOF spectrum analysis. We have successfully applied this approach to identify molds, including dermatophytes, for which diversity is insufficiently represented in commercial databases. This free-access application is available to medical mycologists to improve fungal identification.

In a novel form of IFN-gamma receptor 1 deficiency, cell surface receptors fail to bind IFN-gamma.

Complete IFN-gamma receptor ligand-binding chain (IFNgammaR1) deficiency is a life-threatening autosomal recessive immune disorder. Affected children invariably die of mycobacterial infection, unless bone marrow transplantation is undertaken. Pathogenic IFNGR1 mutations identified to date include nonsense and splice mutations and frameshift deletions and insertions. All result in a premature stop codon upstream from the segment encoding the transmembrane domain, precluding cell surface expression of the receptors. We report herein two sporadic and two familial cases of a novel form of complete IFNgammaR1 deficiency in which normal numbers of receptors are detected at the cell surface. Two in-frame deletions and two missense IFNGR1 mutations were identified in the segment encoding the extracellular ligand-binding domain of the receptor. Eight independent IFNgammaR1-specific mAb's, including seven blocking antibodies, gave recognition patterns that differed between patients, suggesting that different epitopes were altered by the mutations. No specific binding of (125)I-IFN-gamma to cells was observed in any patient, however, and the cells failed to respond to IFN-gamma. The mutations therefore cause complete IFNgammaR1 deficiency by disrupting the IFN-gamma-binding site without affecting surface expression. The detection of surface IFNgammaR1 molecules by specific antibodies, including blocking antibodies, does not exclude a diagnosis of complete IFNgammaR1 deficiency.

[Langerhans cell histiocytosis]. / Histiocytose langerhansienne.

Histiocytosis X, or Langerhans cell histiocytosis (LCH), is a rare disease, with an estimated incidence of 1/200,000 per year in children under 15 years of age. It has a wide clinical spectrum, from single bone involvement (eosinophilic granuloma) to multisystemic disease with organ failure. The treatment of LCH is still controversial. While single system disease may spontaneously recover or requires minimal treatment, some multisystemic disease with organ dysfunction may resist systemic chemotherapy. The mortality rate in this latter subgroup of patients is relatively high and reaches 40% of the cases. A rational approach to the treatment of LCH is based on a better understanding of clinical and pathophysiological features. A prospective multicentre trial including scientific research should be planned, in order to determine the optimal treatment of LCH and to ameliorate the prognosis of the severe unresponsive form of the disease.

[Apparently primary malignant secreting renal lymphoma (immunocytoma)]. / Lymphome malin sécrétant (immunocytome) rénal d'apparence primitive.

The authors report a case of renal lymphoma which secreted a monoclonal Ig M kappa immunoglobulin (immunocytoma) and which was diagnosed on the basis of its secretion. They analyse the problems posed by the indication for surgery, the histological nature, the management and the prognosis.