TROPICAL SPLENOMEGALY SYNDROME

Dr Vishal Dublish; Dr Ira Shah

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Dr Vishal Dublish¹, Dr Ira Shah².

¹Medical Sciences Department, Pediatric Oncall, Mumbai,
²Incharge,Pediatric Tuberculosis, HIV and Liver Clinic, B.J.Wadia Hospital for Children, Mumbai.

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It is also called as big spleen disease. Recently it has been redefined and more appropriately termed as " hyperreactive malarial syndrome" (HMS ).

Etiology: Although malarial parasite is usually not demonstrated in blood smears of patients with HMS, there are convincing evidence linking it to malaria:

Other factors which may play role in development of HMS include genetic susceptibility, malnutrition and pregnancy.

Pathogenesis: Exact mechanism is unknown. Evidence suggests that interaction of repeated malarial infections and unknown host factors leads to production of cytotoxic IgM anti-suppressor lymphocyte (CD8+) antibodies. This leads to exaggerated stimulation of polyclonal B lymphocytes causing excessive and uncontrolled production of IgM (which is polyclonal and not specific for any one particular malaria species) and formation of cryoglobulins (IgM aggregates and immune complexes). These macromolecular aggregates get deposited in Kupffer cells in liver and spleen leading to reticuloendothelial hyperplasia and hepatosplenomegaly (massive and progressive) leading to anemia.

It is prevalent only in malaria endemic areas.
High levels of malarial antibodies can be demonstrated in patients with HMS.
Anti malarial treatment reduces splenic size suggesting response to treatment.
Discontinuation of treatment prematurely may be associated with relapse of HMS.
Effective malarial chemoprophylaxis has been shown to reduce spleen rates as well as incidence of HMS.
Sickle cell trait patients are relatively protected from HMS as with malaria.
Animal models have been developed to show similar clinical syndrome after malarial infection.

Epidemiological factors:

Age: More frequent in young and middle aged adults. Uncommon in children younger than 8 years, suggesting that prolonged chronic antigenic stimulation is an important factor in development of HMS.
Sex: More common in females, male : female = 1:2.

Symptomatology:

Abdominal distention - waxing and waning.
Chronic, dragging pain sensations
Fever is rare, if present it suggests different diagnosis.
Weakness, lethargy
Hernia, leg swellings
Skin and respiratory tract infections
Bleeding episodes - very rare

Signs:
Splenomegaly (moderate to massive & firm and regular). It is the hallmark of HMS.
Splenic bruit may be present
Hepatomegaly
Pallor (without tachycardia)
Abdominal vein dilatation
Cardiomegaly, flow murmurs because of hypervolemia.
Malnutrition
Jaundice may be present, Ascitis uncommon.
Lymphadenopathy absent, parotid enlargement may be seen.

Differential diagnosis:
Kala Azar
Malaria
Histiocytosis
Sickle cell anemia, Thalassemia
Tuberculosis
Infectious mononucleosis
Leukemia, lymphoma, myelofibrosis
Postnecrotic cirrhosis.

Lab studies:
Anemia (normocytic normochromic). Coombs test is negative
Leukopenia
Mild thrombocytopenia
Peripheral smear - malarial parasite not detectable. Increased reticulocyte count.
IgM against malaria increased >2 standard deviation above local mean.
High titers of cold agglutinins, rheumatoid factor, antinuclear factor and cryoproteins.
Phytohemagglutination stimulation test - to differentiate HMS from lymphomas and chronic lymphocytic leukemia.

Histologic findings:
Hepatic sinusoidal lymphocytosis
No malarial pigmentation in macrophages.
Spleen - Kupffer cell hypertrophy and hyperplasia.

Complications:
Infections especially of skin and gastrointestinal tract
Hypersplenism
Predisposition to development of malignancy
Congestive cardiac failure.

Criteria for diagnosis
Major criteria: