Geographic Distribution

In one form or another elephantiasis is seen throughout the tropical world, but the etiology varies. In Ethiopia most elephantiasis is nonfilarial, and this is also true in Kenya. In Uganda and Tanzania elephantiasis may be filarial, nonfilarial or of the idiopathic variety without any involvement of the regional lymph nodes. In some areas of the Congo over 60% of the population are infected with W. bancrofti, but, surprisingly, elephantiasis is not a common problem. In Asia and the islands of the Pacific, especially Samoa, most cases of elephantiasis result from filariasis, but not all: repeated and heavy filarial infections seem to be necessary to cause elephantiasis. Kaposi's sarcoma may also be responsible. Throughout the world various venereal infections may also cause localized elephantiasis of the genitalia.

Etiology and Pathology

Slowing or blockage of the lymphatic flow from a limb or elsewhere results in subacute tissue anoxia, hyperplasia of subcutaneous tissues, and subsequent hyperkeratosis and subcutaneous fibrosis. But elephantiasis is not only the result of obstruction at the lymph nodes. In filariasis, and occasionally in other infections, the lymphatics are also thickened with surrounding edema and inflammatory cell reaction. In many cases there is an associated phlebitis and inflammation in the capillaries, sometimes due to trauma by the worms. By the time elephantiasis has developed there is a profound disturbance of the limb or tissue concerned. The accumulated fluid is almost entirely superficial, and has a high protein content, further increasing the fibrosis. The histopathology is therefore variable, but seldom reversible. In all varieties the lymphatics may be dilated or tortuous or blocked, depending on the stage of the disease. "Tuberculous" elephantiasis tends to involve the whole limb, whereas "pyogenic" lymphedema is more often below the knee, involving the foot and lower leg. The difference depends on which group of nodes is affected. Idiopathic elephantiasis shows no nodal involvement.

When the scrotum is swollen and the limbs are normal, the cause may be filarial or may originate from a urethral stricture with a fistula which has caused chronic infection. There are many other local causes, such as Klebsiella granulomatis, lymphogranuloma venereum, and sparganosis.

Because the common causes of elephantiasis are the filariae, tuberculosis, pyogenic infections, and malignant disease, the frequency of each etiology will vary in different geographic areas.

Laboratory Diagnosis

Serological tests are very useful, but they may be negative in the late stages of filariasis. Aspiration of the lymph nodes or biopsy is the best way to establish the diagnosis with accuracy. In cases of filariasis at the stage of lymphatic varices, the filaria wil be readily identified grossly; specific identification, however, may be more difficult. Microfilariae are absent from the blood in many forms of filariasis and in the fibrotic stage even biopsy may prove unrewarding; further, there is some contraindication to surgery on the lymph nodes because it is likely to further increase the degree of obstruction or may cause a sinus. Tests which depend on stimulating the filariae into the peripheral circulation are dangerous in onchocerciasis and loiasis because there may be severe systemic reactions.

Establishing the etiology of elephantiasis is clinically important but can be very difficult.