December 1991, Volume 41, Issue 12

Original Article

TOXOPLASMIC LYMPHADENITIS A CLINICOPATHOLOGICAL STUDY

Manzoor Ahmad  ( Armed Forces Institute of Pathology, Rawalpindi. )
Javed Iqbal  ( Armed Forces Institute of Pathology, Rawalpindi. )
Adnan Mansoor  ( Armed Forces Institute of Pathology, Rawalpindi. )
Muir Hussain Khan  ( Armed Forces Institute of Pathology, Rawalpindi. )

ABSTRACT

Forty three cases of toxoplasmic lymphadenitis were studied. They constituted 0.5% of all lymphnode biopsies and 4.2% of reactive lymphadenitis. The histological findings supporting a diagnosis of toxoplasmosis were correlated with serological studies. The condition primarily affects young men, causing cervical lymphnode enlargement and varying degrees of fatigue, malaise, cough and fever. It is usually self-limited. This study emphasizes the need for clinicians to consider toxoplasmosis in the differential diagnosis of lymphadenopathies (JPMA 41: 303, 1991).

INTRODUCTION

Since the parasite was first identified in ‘gundi’ (ctenodactylus gundi), later in rabbits and dogs1 in North Africa, toxoplasma gondii has been the subject of much study. The interest was heightenedwith reports by Janku2 who described these parasites in the tissue of an infant with hydrocephalus, who died soon after birth. The histopathologic changes in lymph nodes affected by toxoplasmosis was first described by Robb-Smith3. No study has been published about toxoplasmic lym­phadenitis in Pakistan. Lymph node biopsies in patients with suspected tuberculosis or malignancy at various medical centres of northern Pakistan provided us an opportunity to undertake this study.

MATERIAL AND METHOD

Armed Forces Institute of Pathology receives specimens not only from military hospitals but also from civilian population of the northern Punjab and adjacent part of NWFP. During the past eight years (January, 1983 to December, 1990), lymph node biopsies from 43 patients were diagnosed as consistent with toxoplasmic lym­phadenitis. The histological diagnosis was made on the basis of already established criteria3-6 without prior knowledge of serological results. The clinical data was recorded and patient’s serum was collected for toxoplas­ma antibodies. Blood complete picture and tuberculin test were also carried out. Paraffin section of the cases for light microscopy were fixed in B5 solution or 10% neutral formalin. In addition to routine stains of H&E, PAS and giemsa stains were also used. The serum was stored at -20°C until processed for analysis. IgG antibodies were detected in sera by direct agglutination method. The serological diagnosis was made on the basis of criteria7-11 described.

RESULTS

(a) Clinical findings
Forty-three cases of toxoplasmic lymphadenitis constituted 0.5% of all lymph node biopsies and 4.2% of reactive lymphadenitis diagnosed during the period of study. The ages of the patients ranged between 6 to 42 years (mean 18.8years). Out of43 patients, 28were males and 15 females (M:F ratio 1.8:1). The common occupa tions included students (48.8%), soldiers (18.6%), housewives (11.6%), teachers (9.3%) and drivers (6.9%). The most common manifestation was lymphadenopathy without any symptoms (44%) followed by adenopathy with fatigue and fever (30%). The remaining patients (25%) had adenopathy with cough, malaise and anorex ia. Skin rash and visceromegaly were not present in any case. The duration of the symptoms prior to diagnosis ranged from 1 to 24 months (mean 3 months).

Table I represents the sites of lymphadenopathy. The details of clinical diagnosis are listed in Table II.


(b) Laboratory findings
Thirty-eight patients had normal blood count, five had leukocytosis (16.2 to 19.7 x 109/1). The lymphocytes constituted 48 to 65% of the total count. A mild increase in ESR was seen in all cases (23 to 35 mm at the end of 1st hour - Westergren method). Tuberculin test was positive in twenty-four (55.8%) patients. Toxoplasma antibody (IgG) was positive in all cases. The details of titre are listed in Table III.


(c) Pathological observations
The excised lymph nodes measured 1 to 3 cm in diameter and firm in consistency. Histologic findings included reactive follicular hyperplasia, associated with presence of irregular clusters of epithelioid histiocytes, located usually in cortical and paracortical zones. These cefls characteristically encroached upon and blurred the margins of germinal centres. Epithelioid cells were also seen frequently within the germinal centres (Figures 1 and 2).


An additional feature was distention of cortical and marginal sinuses by monocytoid cells. The special
stains yielded no ‘cysts’.
(d) Prognosis and followup
The disease resolved spontaneously (4-12 weeks) in twenty-six cases (60.4%). The remaining seventeen cases responded to combination of sulphadiazine (3 gm/day) and pyrimethamine (25-50 mg/day) for 14 to 28 days. The disease resolved without any residual com­plications.

DISCUSSION

Toxoplasmosis is an infectious disease affecting man and other warm blooded vertebrates throughout the world, although the frequency of such infections varies considerably from country to country and within a country1,2,4,7,10,12-14. It is caused by protozoan parasite toxoplasma gondii, an obligate intracellular protozoan. The parasite is coccidian of cats, the definitive host. Toxoplasmosis in humans has developed through several stages. In the past, it was regarded as a minor infection. However, extensive media attention in the late eighties made the medical and scientific communities appreciate the growing importance of toxoplasmic infec­tion in humans. McCabe and Remington12-14 divided clinical toxoplasmosis into various types. Toxoplasmic lymphadenitis is the most common clinical type of acquired toxoplasmosis16,17. However, other types may be associated with lymphadenopathy. Toxoplasmosis with lymphadenopathy as the presenting symptom has been well described4,15,17. The lymphadenopathy is usually generalized; however, the cervical and suboccipital are often most prominent. They are painless3,4. The duration of lymphadenopathy is extremely variable, ranging from days to over a year. Our cases generally conformed to this pattern. Nonpruritic maculopapular rash and visceromegaly was reported in other studies3,4,13,17, but was not seen in our cases. Present cases demonstrate a spectrum of symptoms, from completely asymptomatic patients to the prolonged illness with fever, anorexia, chills and cough. Malaise, fatigue and weakness are often quite pronounced. This clinical pattern was also reported in other studies3,4,6,13,17. In this study, the disease primarily affected young men. The likelihood of toxoplasmosis increases with age, perhaps because of an increased cumulative exposure to infection as one gets older7,13. The young men in our community are particularly exposed to undercooked meat, unpasteurized milk and/or contaminated water. The histological changes in lymph nodes affected by toxoplasmosis were described by Robb-Smith, but he was unaware of the underlying cause3. Pringer-Kuchinka and Sexan independently but simultaneously described the characteristic histologic changes that occur in toxoplasmic lymphadenitis3,4,6,17. They emphasize the striking degree of reactive follicular hyperplasia as­sociated with numerous mitosis in the germinal centres and presence of many freshly necrotic cells, so that the centres are littered with karyorrhectic particles of nuclear debris. The inter- follicular, cortical and paracor­tical zones contain clusters of epithelioid cells (his­tiocytes with vesicular nuclei and abundant eosinophilic cytoplasm). These cells are not arranged in well delimited tuberculioid follicles and very rarely associated with giant cells (foreign body/langhans type). They often and characteristically encroach upon and blur the margins of the reactive folicles and occur singly or in clusters in the germinal centre. These characteristic histological pic­tures of toxoplasmic lymphadenopathy were constantly seen in our cases. Occasionally similar collections of histiocytes are seen in lymph nodes of patients with Hodgkin’s dis­ease3,17. Although necrosis is common Hodgkin’s disease, it is not characteristic of toxoplasmic lymphadenitis6,15. In other lymphadenitis like that of Whipple’s disease18, infectious mononucleosis3, Kikuchi’ s lymphadenitis15 and Leishmaniasis6. aggregates of histiocytes similar to those seen in toxoplasmic lymphadenitis are also found. These clusters of histiocytes, therefore, may suggest the diagnosis, but do not make it definitive. If associated with high serological titer, they enable a surgical pathologist to diagnose toxoplasmic lymphadenitis with con­fidence1,3,4,15. Since toxoplasmic ‘cysts’ are rarely ob­served in histologic section3-5.16-18. The prognosis was excellent in our cases. The disease resolved in weeks to months without any residual complication. Occasionally disease recurs or may per­sist4,17. The acute infection during pregnancy may result in severe consequences of congenital toxoplasmosis14,19. Seroepidemiological study at Karachi10 confirms toxoplasma antibodies, 39.8% in pregnancy wastage group and 25.5% in congenitally abnormal group. Another study from northern Pakistan20 reported that infection rate in pregnant women was highest in Punjab (63%) followed by Azad Kashmir(48%) and NWFP (38%). This indicates the widespread prevalence of parasite in our population. To conclude, toxoplasmosis is not an uncommon cause of lymphadenopathies as this is found in 4.2% of reactive lymphadenitis. It must be considered in the differential diagnosis of lymphadenopathy. The distinc­tive histopathological changes in affected lymph node could prevent the misdiagnosis of more serious condi­tions like Hodgkin’s disease. The morphology, however, must be correlated with high serological titre, in order to make a definitive diagnosis.

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