Inflammatory myopathies

Severe rhabdomyolysis due to idiopathic inflammatory myopathies, a wary manifestation of a heterogenous pathology

Idiopathic inflammatory myopathies (IIM) are historically classified by The Bohan and Peter criteria. The presentation of IIM is versatile and clinical-serological findings can aid in diagnosing the underlying form of IIM. Over the past years, the discovery and the use of myositis-specific autoantibodies (MSA) and myositis-associated autoantibodies (MAA) have led to a more heterogeneous classification by the European League Against Rheumatism and American College of Rheumatology (EULAR/ACR).This paper describes a case of dermatomyositis sine dermatitis. A 70-year -old woman presented with complaints of muscle weakness and was admitted because of severe oliguric renal failure due to rhabdomyolysis. Despite treatment with hemodialysis and initial recovery, her clinic worsened again. The disease course in combination with electromyography findings, PET-scan results, and positive myositis-specific autoantibodies, that is, anti-NXP-2 antibodies, ultimately led to the diagnosis.Today, commercial kits based on line immunoassay and dot blot have mostly replaced the labor-intensive immunoprecipitation of RNA and/or proteins for detecting MSA. Though it makes routine testing of multiple MSA easy to implement in clinical practice, more validation studies are required and clinicians should be aware of its limitations, including false-positive results. When clinical suspicion for IIM is high, a negative screening for antinuclear antibodies (ANA) result does not exclude IIM and the first test of choice remains a multi-specific immunoassay for the whole spectrum of MSA.In this paper, we want to underline that there is no shortcut in diagnosing IIM. Caution is required in interpreting different EMG, PET-scan, histological, and laboratory findings. Especially in the case of rhabdomyolysis, as this is a severe and wary manifestation of myositis.

Myofasciitis in the Domestic Ferret

Since late 2003, an inflammatory disease of muscle and fascia has been diagnosed in several ferrets at Northwest ZooPath, and this report describes the condition in 17 ferrets. It is a disease of young ferrets, characterized by rapid onset of clinical signs, high fever, neutrophilic leukocytosis, treatment failure, and death (or euthanasia). Gross lesions include atrophy of skeletal muscle; red and white mottling and dilatation of the esophagus; and splenomegaly. Histologically, moderate to severe suppurative to pyogranulomatous inflammation is in the skeletal muscle and the fascia at multiple sites, including esophagus, heart, limbs, body wall, head, and lumbar regions. Myeloid hyperplasia of spleen and/or bone marrow also is a prominent feature. Ultrastructural lesions include mitochondrial swelling, intracellular edema, disruption of myofibrils and Z bands. Bacterial and viral cultures, electron microscopy, immunohistochemistry, and polymerase chain reaction were negative for a variety of infectious agents. The clinical presentation and distribution of lesions suggests that polymyositis in domestic ferrets is likely a distinct entity. The etiopathogenesis if this condition is not known.

Disseminated idiopathic myofasciitis in ferrets

First described in 2003, disseminated idiopathic myofasciitis (DIM) has emerged as a new disease in young, domestic ferrets. DIM is a severe inflammatory condition that affects primarily muscles and surrounding connective tissues. The disease is characterized by rapid onset of clinical signs, high fever, neutrophilic leukocytosis, and general lack of response to therapeutic intervention. Until recently DIM was considered fatal, but a few surviving ferrets indicate there may be an effective treatment protocol. DIM is suspected to be an immune-mediated disease, but the etiopathogenesis is not known. This article reviews clinical and pathologic findings in DIM patients, covers recommended diagnostic procedures and clinical management of ferrets with DIM, and discusses potential etiologies for this newly recognized disease in ferrets.