Myocarditis is an uncommon complication of toxoplasma infection.

Acquired or congenital infection may result in toxoplasma cysts forming within heart muscle, which may or may not give rise to cardiac symptoms such as myocarditis, pericarditis, or pericardiac effusion.

Diagnosis of toxoplasma myocarditis is difficult, unless other symptoms of generalised toxoplasmosis are present, in which case dye test titres will probably be high and IgM present.

If the cardiac symptoms are isolated, dye test titres may be within the normal range but a diagnosis may be made if there is a rising titre or IgM present, or a response to anti-toxoplasma therapy. If there is a pericardiac effusion, toxoplasma organisms may be identified or isolated from the fluid.