Juvenile dermatomyositis and other idiopathic inflammatory myopathies of childhood

Lymphadenopathy is the most frequent clinical manifestation of acute acquired infection with Toxoplasma in the immunocompetent individual. One hundred seven cases of histologically verified toxoplasmic lymphadenitis were reviewed in an effort to determine the usual modes of clinical presentation and the incidence of extranodal disease. Toxoplasmic lymphadenitis most frequently involved a solitary lymph node in the head and neck regions, without systemic symptoms or extranodal disease and with a benign clinical course. However, serious extranodal disease did occur in some patients and included myocarditis, pneumonitis, encephalitis, chorioretinitis, and transmission of the infection to the fetus. Case histories are presented to illustrate important points with respect to clinical presentation, complications, and diagnosis.

Clinical Spectrum in 107 Cases of Toxoplasmic Lymphadenopathy

Publisher Summary There are four tissue cyst-forming protozoan organisms known to parasitize vertebrate hosts: (1) Toxoplasma , a ubiquitous parasite with a predilection for the central nervous system of numerous homeotherms including man; (2) Besnoitia , which forms cysts in various tissues of ungulates, rodents, and reptiles; (3) Sarcocystis , which as the name implies, parasitizes predominantly the musculature and is remarkably common in mammals, birds, and reptiles; and (4) Frenkelia , which forms cysts in the brains of rodents belonging to several genera. The recognition of the tissue cysts of all four organisms as intermediate stages in the heteroxenous life cycles of coccidian parasites of various carnivores, and the consequent central role of the oocyst in their route of transmission, necessitates a reappraisal of understanding of the epidemiology and epizootiology of infection with these organisms in the light of the dynamics of transmission of the classic eimeriid coccidia. The chapter reviews recent advances made in the study of life cycles and other biological aspects of the tissue stage-forming eimeriid coccidians and throws some light on the problem of their classification.

Current Concepts on the Biology, Evolution and Taxonomy of Tissue Cyst-forming Eimeriid Coccidia

Human idiopathic inflammatory myopathy is an acquired disorder with an annual incidence of two to five cases per million. A genetic influence of two to five cases per million. A genetic influence on host susceptibility may also play a role. With the marked heterogeneity of the disease one of the major challenges is to identify subsets that might share a more uniform pathogenesis and manifest a less diverse profile of clinical findings, histopathological abnormalities, and natural history. Dermatomyositis can be distinguished by clinical appearance and pathological changes, but the recognition of additional disease subsets remains very inexact. Current evidence suggests that dermatomyositis occurs as a result of a vasculopathy, but immune mechanisms involved in other categories of idiopathic inflammatory myopathy may also involve cell-mediated immunity and possibly multiple mechanisms. Even though viral-induced muscle inflammation occurs in humans, there is no convincing evidence for a viral cause of idiopathic inflammatory myopathy. Experimental allergic myositis may be produced by the injection of animals with skeletal muscle homogenates and complete Freund's adjuvant, but the myositogenic factor is unknown and the parallels between experimental allergic myositis and human idiopathic inflammatory myopathy are limited.

Inflammatory myopathy: a review of etiologic and pathogenetic factors.

Adult and juvenile dermatomyositis share the hallmark features of pathognomic skin rash and muscle inflammation, but are heterogeneous disorders with a range of additional disease features and complications. The frequency of important clinical features such as calcinosis, interstitial lung disease and malignancy varies markedly between adult and juvenile disease. These differences may reflect different disease triggers between children and adults, but whilst various viral and other environmental triggers have been implicated, results are so far conflicting. Myositis-specific autoantibodies can be detected in both adults and children with idiopathic inflammatory myopathies. They are associated with specific disease phenotypes and complications, and divide patients into clinically homogenous subgroups. Interestingly, whilst the same autoantibodies are found in both adults and children, the disease features remain different within autoantibody subgroups, particularly with regard to life-threatening disease associations, such as malignancy and rapidly progressive interstitial lung disease. Our understanding of the mechanisms that underlie these differences is limited by a lack of studies directly comparing adults and children. Dermatomyositis is an autoimmune disease, which is believed to develop as a result of an environmental trigger in a genetically predisposed individual. Age-specific host immune responses and muscle physiology may be additional complicating factors that have significant impact on disease presentation. Further study into this area may produce new insights into disease pathogenesis.

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Adult and juvenile dermatomyositis: are the distinct clinical features explained by our current understanding of serological subgroups and pathogenic mechanisms?

SUMMARY

A woman had the typical clinical, cutaneous, and muscular picture of dermatomyositis but without some of the biochemical alterations of that disease. The positive serological investigations for toxoplasmosis, the presence in muscles of very numerous toxoplasms and their culture in mice, and the improvement after treatment with pyrimethamine and sulphamethoxypyridine demonstrated that the signs of dermatomyositis had been caused by infection with toxoplasmosis.

Luciana D'alessandro

Papers

Dermatomyositis-like syndrome due to toxoplasma.