Curvilinear membranous formations in lymph node cells of an African AIDS patient with tuberculosis

Tissue from an extirpated cervical lymph node of an African AIDS patient with tuberculosis was investigated with the electron microscope. A peculiar cytoplasmic structure was found in histiocytic cells of the lymph node tissue. This structure consisted of a loose aggregation of convoluted, folded curvilinear membranes, demonstrating C-shaped, U-shaped, and S-shaped profiles according to the plane of section. These curvilinear membranous formations (CMF) were formed by 2 parallel-running unit membranes separated by a narrow electron-lucent space. Continuities of CMF with rough-surfaced endoplasmic reticulum were sometimes observed. Occasionally, an electron-dense, blurred cytoplasmic area was seen between 2 neighboring CMF. Several CMF also formed a seastar-like configuration by mergence in such an area. It is unknown whether the HIV infection of the patient was the primary cause of the CMF.