Toxoplasma cervical adenitis

            Toxoplasmosis is a disease caused by the parasite Toxoplasma gondii. More than 60 million people in the U.S. harbor the parasite; however, most are asymptomatic carriers (1). The primary host of the parasite is the cat, and individuals may acquire the parasite through infected cat waste; however, the more common source for human infection is through contact with raw meat.

The infection produces a wide range of clinical syndromes in humans, land and sea mammals, and various bird species. 80-90% of infected individuals have no symptoms (1). If signs of infection develop, they start after 1-2 weeks and consist of flu-like symptoms with sore throat, lymphadenitis and muscle aches, accompanied by laboratory tests showing lymphocytosis with atypical lymphocytes (2). Most immunocompetent individuals recover with no sequelae, but a small percentage of patients (immunocomprised, newborns) may eventually develop complications including chorioretinitis, encephalitis, or, rarely, myocarditis and polymyositis. Infants may be infected by cross-placental transmission of the parasite.

            In immunocompetent symptomatic patients, the commonest presenting sign of acquired toxoplasmosis is enlargement of superficial lymph nodes (1). Toxoplasma adenitis usually occurs in the neck, and is persistent: from one to four months in 85% of patients, and for a longer period in the remainder.        

                Differential diagnosis of persistent cervical adenopathy includes malignancy (especially lymphoma) and other infectious and inflammatory diseases. In a large series from a lymphadenopathy referral center, toxoplasmosis accounted for slightly more than 10% of inflammatory causes of adenopathy (3). In another series of patients with granulomatous adenitis, about 10% were identified as toxoplasmosis (4). The primary method of diagnosis is based on antibody testing. Titers of >1:1024 (or >300 ELISA units) indicate acute infection. Titers between 1:16 and 1:256 (or <300 ELISA units) are less certain and require demonstration of rising titers. High serologic titers are considered most conclusive in diagnosing this usually self-limited infection.  

 At times cytology or histology of an involved node is necessary for definitive diagnosis. Toxoplasma gondii may be demonstrated in infected tissue. The microscopic findings of non-caseating granulomas further suggest toxoplasmosis; since granulomas may be found in malignancy, the background cell population also needs to be examined. FNA cytology is a valuable tool for the diagnosis of toxoplasmic lymphadenitis, and Papanicolaou stain is appropriate for demonstration of the parasite. Typical FNA features including presence of follicular hyperplasia with secondary germinal centres rich in macrophages, presence of groups of epithelioid cells and presence of monocytoid histiocytes (4,5,6).

Toxoplasma cervical adenitis should be included in the differential diagnosis of persistent symptoms.