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The clinical expression of lymphatic filariasis varies considerably. Most infected persons are asymptomatic. Even in asymptomatic people, adult filarial worms commonly cause subclinical lymphatic dilatation and dysfunction. Filarial lymphadenopathy is seen commonly in infected children; before puberty, adult worms can be detected by ultrasonography of the inguinal, crural, and axillary lymph nodes and vessels. Death of the adult worm triggers an acute inflammatory response, which progresses distally (retrograde) along the affected lymphatic vessel, usually in the limbs and is termed acute filarial lymphangitis. If present, systemic symptoms, such as headache or fever, are generally mild.
In postpubertal males, adult Wuchereria bancrofti organisms are found most commonly in the intrascrotal lymphatic vessels and can be visualized on ultrasound examination. Inflammation resulting from adult worm death, in this area, may present as funiculitis, epididymitis, or orchitis. A tender granulomatous nodule may be palpable at the site of the dead adult worms.
The chronic manifestations of lymphedema and/or hydrocele will develop in approximately 30% of LF-infected persons. Lymphedema mostly affects the legs, but can also occur in the arms, breasts, and genitalia. Most people develop these symptoms years after infection has cleared. Recurrent secondary bacterial infections of the affected extremity, characterized by severe pain, fever and chills, hasten the progression of lymphedema to its advanced stage, known as elephantiasis.
Filarial hydrocele is thought to be the consequence of lymphatic damage caused by adult worms. Chyluria, which results from rupture of dilated lymphatics into the renal pelvis, can occur as a manifestation of bancroftian filariasis. Microscopic hematuria and proteinuria are also found in LF infected patients.
Cough, fever, marked eosinophilia, high serum immunoglobulin E concentrations, and positive antifilarial antibodies are manifestations of the tropical pulmonary eosinophilia (TPE) syndrome. Peripheral microfilaremia is absent in patients with TPE. Most cases of TPE have been reported in long-term residents from Asia. Men 20 to 40 years old are most commonly affected.
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