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Dr. Kosaku Nitta, Department of Medicine, Kidney Center, Tokyo Women’s Medical College, 8-1 Kawada-cho, Tokyo 162 (Japan) Dear Sir, Membranous lipodystrophy is the name previously given by Nasu et al. [1] to a rare disease in which cyst-lesions of adipose tissue, including that of long bones, occur together with sudanophilic leukoencephalopa-thy. This disease has recently been recognized as hereditary and is characterized by polycystic changes in many bones, with a variety of central nervous system changes due to impairment of lipid metabolism by an unknown mechanism [2-6]. Histopathological diagnosis is possible by biopsying bone marrow or synovial tissue. The adipose cells of the bone marrow, synovial membrane and other sites are replaced by convoluted, hyaline, eosinophilic membranes of variable thickness that enclose large spaces. The membranes are positive for periodic acid-Schiff staining but negative for resorcinol-fuchsin staining for elastic tissue. Masson’s trichrome and Azan-Mallory stain the membranes blue or red. In frozen sections, the membranes and the contents of the cyst-like spaces are Sudan III positive [7]. We have found exactly the same mem-branocystic changes in subcutaneous tissue close to arteriovenous shunts in 93 of 100 cases in hemodialysis patients with carpal tunnel syndrome. The average duration of hemodialysis was 12.6 years, and the average age of the patients was 52.2 years (male:fe-male = 54:39). These changes were quite abundant in the synovial tendon sheaths (89.5%) but minimal in the tendons ( < 1%). Conventional histochemical studies revealed an eosinophilic hyaline substance in all synovial tendon sheaths. Most of the membranocystic lesions contained material positive for Masson’s trichrome stain (fig. la). The membranes of the membranocystic changes appeared markedly convoluted, and the thickness of the membrane varied from lesion to lesion. As summarized in table 1, they stained red with Masson’s trichrome, were periodic acid-Schiff positive, stained blue with Luxol fast blue, were Sudan black B positive but negative for Al-cian blue (pH 1.0) and the resorcinol-fuchsin stain. The tissues did not stain with Congo red. No ß2-microglobulin was found by the peroxidase-antiperoxidase method. Interestingly, they reacted with antisera against amyloid P component and neuraminidase. Occasional macrophage-like cells were present