Lipomatosis of Nerve

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ipomatosis of nerve (LN) is a rare and challenging disorder with only a few case reports or small case series in literaL ture. Mason described this condition in 1953 and later Johnson and Bonfiglio further described it in 1969 (7, 10). It is a benign tumor due to proliferation of mature adipocytes with a propensity for progressive growth. Most of the cases occur in patients younger than age 30 years of age. LN also causes enlargement of digits due to fat deposition between the nerve fascicles and increased growth of skin. LN when associated with true macrodactyly is called as macrodystrophia lipomatosa. Macrodystrophia lipomatosa is twice as common in females compared to males. LN without macrodactyly affects males and females equally (1, 9).Median nerve and its branches are involved in 85%of cases of LN (2). Guthikonda et al. classified lipomatousmasses of a nerve into 4 types: soft tissue lipoma, intraneural lipoma, LN, and macrodystrophia lipomatosa (6). Soft tissue lipomas cause external compression of a nerve. Intraneural lipomas, on the other hand, arewell capsulatedwith a good plane of separation from the peripherally displaced nerve fascicles. Macrodystrophia lipomatosis is excessive growth or fatty infiltration of all mesenchymal structures such as skin and bones. LN is fat deposition between the nerve fascicles. The exact etiopathogenesis of LN is unknown. The possible implicated causes are trauma, chronic nerve irritation, abnormal development of flexor retinaculum, and can be a congenital condition (6, 10, 12). A recent paper has implicated somatic gain-of-function mutation in the PI3K/AKT cellsignaling pathway, regulating apoptosis (11).