Department of Infectious and Parasitic Diseases Pathology and the World Health Organization Reference Laboratory for Filarial Infections of Man, Armed Forces Institute of Pathology, Washington, D.C. 20306
The World Health Organization's Collaborating Centre for the Histopathology of Filarial Diseases of Man contains specimens of lymph node from 13 patients infected by the filarial nematode Loa loa. Ten of these nodes have distinctive microscopic features characterized by distended sinuses that contain histiocytes and eosinophils and by atrophy of lymphoid follicles. Less striking features include fibrosis of capsule and trabeculae, dilated lymphatic vessels of capsule and medulla, and inflammatory cell infiltrates. We believe that these changes, although in themselves nonspecific, are characteristic of lymphadenitis caused by Loa loa. These 10 lymph nodes were removed from the inguinal region — one from each of 10 native Zairians. At the time of herniorrhaphy the nodes in eight patients were found to be enlarged and were removed for diagnosis. Seven of the 10 patients were infected with Dipetalonerna perstans as well as Loa loa, and one of these seven had three filarial infections — L. loa, D. perstans and D. streptocerca. Lymph nodes from other patients infected by other filariae that were available for study at the AFIP did not have these histopathologic features.