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Lipedema is a painful fat disease of loose connective tissue usually misdiagnosed as lifestyle-induced obesity that affects ~10% of women of European descent as well as other populations. Lipedema is characterized by symmetric enlargement of the buttocks, hips, and legs due to increased loose connective tissue; arms are also affected in 80% of patients. Lipedema loose connective tissue is characterized by hypertrophic adipocytes, inflammatory cells, and dilated leaky blood and lymphatic vessels. Altered fluid flux through the tissue causes accumulation of fluid, protein, and other constituents in the interstitium resulting in recruitment of inflammatory cells, which in turn stimulates fibrosis and results in difficulty in weight loss. Inflammation and excess interstitial substance may also activate nerve fibers instigating the painful lipedema fat tissue. More research is needed to characterize lipedema loose connective tissue structure in depth, as well as the form and function of blood and lymphatic vessels. Understanding the pathophysiology of the disease will allow healthcare providers to diagnose the disease and develop treatments.

Background: Lipedema and Dercum's disease (DD) are incompletely characterized adipose tissue diseases, and objective measures of disease profiles are needed to aid in differential diagnosis. We hypothesized that fluid properties, quantified as tissue water bioimpedance in the upper and lower extremities, differ regionally between these conditions. Methods and Results: Women (cumulative n = 156) with lipedema (n = 110), DD (n = 25), or without an adipose disease matched for age and body mass index to early stage lipedema patients (i.e., controls n = 21) were enrolled. Bioimpedance spectroscopy (BIS) was applied to measure impedance values in the arms and legs, indicative of extracellular water levels. Impedance values were recorded for each limb, as well as the leg-to-arm impedance ratio. Regression models were applied to evaluate hypothesized relationships between impedance and clinical indicators of disease (significance criteria: two-sided p < 0.05). Higher extracellular water was indicated (i) in the legs of patients with higher compared with lower stages of lipedema (p = 0.03), (ii) in the leg-to-arm impedance ratio in patients with lipedema compared with patients with DD (p ≤ 0.001), and (iii) in the leg-to-arm impedance ratio in patients with stage 1 lipedema compared with controls (p ≤ 0.01). Conclusion: BIS is a noninvasive portable modality to assess tissue water, and this device is available in both specialized and nonspecialized centers. These findings support that regional bioimpedance measures may help to distinguish lipedema from DD, as well as to identify early stages of lipedema.

Background and Aim: Lipedema is a common painful SAT disorder characterized by enlargement of fat primarily in the legs of women. Case reports of lipedema tissue samples demonstrate fluid and fibrosis in the interstitial matrix, increased macrophages, and adipocyte hypertrophy. The aims of this project are to investigate blood vasculature, immune cells, and structure of lipedema tissue in a cohort of women. Methods: Forty-nine participants, 19 controls and 30 with lipedema, were divided into groups based on body mass index (BMI): Non-Obese (BMI 20 to <30 kg/m2) and Obese (BMI 30 to <40 kg/m2). Histological sections from thigh skin and fat were stained with H&E. Adipocyte area and blood vessel size and number were quantified using ImageJ software. Markers for macrophages (CD68), mast cells (CD117), T cells (CD3), endothelial cells (CD31), blood (SMA), and lymphatic (D2-40 and Lyve-1) vessels were investigated by IHC and IF. Results: Non-Obese Lipedema adipocyte area was larger than Non-Obese Controls (p=0.005) and similar to Obese Lipedema and Obese Controls. Macrophage numbers were significantly increased in Non-Obese (p < 0.005) and Obese (p < 0.05) Lipedema skin and fat compared to Control groups. No differences in T lymphocytes or mast cells were observed when comparing Lipedema to Control in both groups. SMA staining revealed increased dermal vessels in Non-Obese Lipedema patients (p < 0.001) compared to Non-Obese Controls. Lyve-1 and D2-40 staining showed a significant increase in lymphatic vessel area but not in number or perimeter in Obese Lipedema participants (p < 0.05) compared to Controls (Obese and Non-Obese). Areas of angiogenesis were found in the fat in 30% of lipedema participants but not controls. Conclusion: Hypertrophic adipocytes, increased numbers of macrophages and blood vessels, and dilation of capillaries in thigh tissue of non-obese women with lipedema suggest inflammation, and angiogenesis occurs independent of obesity and demonstrates a role of altered vasculature in the manifestation of the disease.

Background: Lipedema and Dercum's disease (DD) are incompletely characterized adipose tissue diseases, and objective measures of disease profiles are needed to aid in differential diagnosis. We hypothesized that fluid properties, quantified as tissue water bioimpedance in the upper and lower extremities, differ regionally between these conditions. Methods and Results: Women (cumulative n = 156) with lipedema (n = 110), DD (n = 25), or without an adipose disease matched for age and body mass index to early stage lipedema patients (i.e., controls n = 21) were enrolled. Bioimpedance spectroscopy (BIS) was applied to measure impedance values in the arms and legs, indicative of extracellular water levels. Impedance values were recorded for each limb, as well as the leg-to-arm impedance ratio. Regression models were applied to evaluate hypothesized relationships between impedance and clinical indicators of disease (significance criteria: two-sided p < 0.05). Higher extracellular water was indicated (i) in the legs of patients with higher compared with lower stages of lipedema (p = 0.03), (ii) in the leg-to-arm impedance ratio in patients with lipedema compared with patients with DD (p ≤ 0.001), and (iii) in the leg-to-arm impedance ratio in patients with stage 1 lipedema compared with controls (p ≤ 0.01). Conclusion: BIS is a noninvasive portable modality to assess tissue water, and this device is available in both specialized and nonspecialized centers. These findings support that regional bioimpedance measures may help to distinguish lipedema from DD, as well as to identify early stages of lipedema.

Syndromes with localized accumulation of subcutaneous fatty tissue belong to a group of genetically and phenotypically heterogeneous disorders. These diseases may show some common signs, such as nodular fat, symmetrical fat masses, obesity, fatigue, lymphedema and symmetrical lipomas (painful or otherwise). Other symptoms may be specific for the different clinical entities, enabling correct differential diagnosis. Disorders belonging to this spectrum are lipedema, generalized diffuse or nodular forms of Dercum disease, localized nodular Dercum disease and multiple symmetric lipomatosis. Here we summarize the genes involved in syndromes with localized accumulation of subcutaneous fat and the test we use for genetic analysis.

Subcutaneous adipose tissue diseases involving adipose tissue and its fascia, also known as adipofascial disorders, represent variations in the spectrum of obesity. The adipofascia diseases discussed in this chapter can be localized or generalized and include a common disorder primarily affecting women, lipedema, and four rare diseases, familial multiple lipomatosis, angiolipomatosis, Dercum disease, and multiple symmetric lipomatosis. The fat in adipofascial disorders is difficult to lose by standard weight loss approaches, including lifestyle (diet, exercise), pharmacologic therapy, and even bariatric surgery, due in part to tissue fibrosis. In the management of obesity, healthcare providers should be aware of this difficulty and be able to provide appropriate counseling and care of these conditions. Endocrinologists and primary care providers alike will encounter these conditions and should consider their occurrence during workup for bariatric surgery or hypothyroidism (lipedema) and in those that manifest, or are referred for, dyslipidemia or diabetes (Dercum disease). People with angiolipomas should be worked up for Cowden’s disease where a mutation in the gene PTEN increases their risk for thyroid and breast cancer. This chapter provides details on the pathophysiology, prevalence, genetics and treatments for these adipofascial disorders along with recommendations for the care of people with these diseases. For complete coverage of all related areas of Endocrinology, please visit our on-line FREE web-text, WWW.ENDOTEXT.ORG.