Lesser known mycobacteria

Mycobacterium celatum, an emerging pathogen and cause of false positive amplified mycobacterium tuberculosis direct test

Mycobacterium celatum is a recently described organism. Herein we describe a case of M. celatum lymphadenitis in an immunocompetent child and the first reported case of a M. celatum infection (lung abscess) in a transplant recipient. A literature review identified 19 other cases of M. celatum infection. Fifteen occurred in patients with the acquired immunodeficiency syndrome. Of these, nine were disseminated and six were localized (primarily to the lungs). The remaining 4 patients were immunocompetent and had localized infection (pneumonitis or lymphadenitis). Diagnosis of M. celatum infection can be challenging as M. celatum can cause false-positive results with the current version of the Amplified Mycobacterium tuberculosis Direct Test (Gen-Probe, San Diego, CA.). Definitive identification is available by DNA sequencing or high-performance liquid chromatography. M. celatum can cause infection in immunocompromised and immunocompetent hosts.

Molecular epidemiology of Mycobacterium malmoense infections in Scotland

Clinical isolates of Mycobacterium malmoense collected over 5 years from patients across Scotland with a variety of diseases have been characterized by pulsed-field gel electrophoresis (PFGE), ribotyping, and 16S ribosomal DNA gene sequencing. Results indicate that this species harbors little genetic diversity and that the different strain types that were identified by PFGE showed no correlation with geographical origin or date of isolation.

Macrophagic myofasciitis: an emerging entity. Groupe d'Etudes et Recherche sur les Maladies Musculaires Acquises et Dysimmunitaires (GERMMAD) de l'Association Française contre les Myopathies (AFM)

BACKGROUND

An unusual inflammatory myopathy characterised by an infiltration of non-epithelioid histiocytic cells has been recorded with increasing frequency in the past 5 years in France. We reassessed some of these cases.

METHODS

We did a retrospective analysis of 18 such cases seen in five myopathology centres between May, 1993, and December, 1997. The myopathological changes were reassessed at a clinopathology seminar.

FINDINGS

Detailed clinical information was available for 14 patients. The main presumptive diagnoses were polymyositis and polymyalgia rheumatica. Symptoms included myalgias in 12 patients, arthralgias in nine, muscle weakness in six, pronounced asthenia in five, and fever in four. Abnormal laboratory findings were occasionally observed, and included raised creatine kinase concentrations, increased erythrocyte sedimentation rate, and myopathic electromyography. Muscle biopsy showed infiltration of the subcutaneous tissue, epimysium, perimysium, and perifascicular endomysium by sheets of large macrophages, with a finely granular PAS-positive content. Also present were occasional CD8 T cells, and inconspicuous muscle-fibre damage. Epithelioid and giant cells, necrosis, and mitotic figures were not seen. The images were easily distinguishable from sarcoid myopathy and fasciitis-panniculitis syndromes. Whipple's disease, Mycobacterium avium intracellulare infection, and malakoplakia could not be confirmed. Ten patients were treated with various combinations of steroids and antibiotics; symptoms improved in eight patients, and stabilised in two.

INTERPRETATION

A new inflammatory muscle disorder of unknown cause, characterised by a distinctive pathological pattern of macrophagic myofasciitis, is emerging in France.