Deep phenotyping to improve understanding of causal mechanisms and underlying gene mutations in primary lymphoedema and lymphatic malformations

淋巴水肿是由淋巴系统故障或阻塞引起的任何身体部位的肿胀，是医疗保健中最被忽视的领域之一。数据显示，它的发病率是1型糖尿病的两倍（据估计，英国有40万人患有1型糖尿病），但人们对它的认识要少得多。原发性淋巴水肿通常被认为是遗传性的，而继发性淋巴水肿有一个明确的原因，如因癌症而手术切除淋巴腺。在过去的5年里，已经确定了一些基因，当这些基因有缺陷时，会导致遗传性淋巴水肿。找到致病基因意味着可以通过对疑似患有特定类型淋巴水肿的患者的DNA进行血液检查来做出特定的诊断。这有助于告知患者他们的病情以及他们一生中可能发生的事情。我们研究淋巴水肿已经30多年了。通过调查与淋巴水肿密切匹配的患者的DNA，基因已经被发现。详细的临床病史和检查结果记录，但临床表现往往不足以区分一种类型的原发性淋巴水肿与另一种。本研究旨在提供更好的研究方法，以帮助区分不同类型的原发性淋巴水肿，并使我们更好地了解产生淋巴水肿的机制（从而有助于设计新的治疗方法）。目前用于调查淋巴水肿的工具非常有限。淋巴显像是NHS内唯一广泛可用的诊断淋巴水肿的方法，但它不能直接观察淋巴管。提出了两种方法来克服这一问题。第一种是磁共振淋巴管造影（MRL），使用注射造影剂，可以区分淋巴管和血管。核磁共振成像也将被用来观察体内畸形的淋巴管。第二种检查方法是吲哚菁绿色淋巴造影（ICGL）。这涉及到一种染料的注入，这种染料可以在近红外光谱波长的光中被相机看到。在淋巴显微手术之前，ICGL已被用于对手臂或腿部皮肤下的淋巴管进行成像，但从未用于原发性淋巴水肿的研究。MRL能够成像更深层次的淋巴管，而ICGL将提供淋巴管泵送和瓣膜功能的信息。与淋巴显像不同，MRL和ICGL都不涉及放射。为了研究皮肤中较小的淋巴毛细血管，我们将进行活组织检查，并使用革命性的、最先进的3D成像技术对它们进行分析。这将告诉我们更多的结构和功能故障的小淋巴管在病人组。感染可能是淋巴水肿的毁灭性后果，因为淋巴系统是我们免疫系统的一部分，所以当淋巴系统出现问题时，免疫功能也会出现问题。我们已经表明，在某些遗传形式的淋巴水肿中，淋巴系统的白细胞（淋巴细胞）数量较少。实际上，没有对人类的研究来解释为什么会这样。我们计划研究淋巴细胞的数量，运输和功能，以了解免疫功能障碍是基因的结果还是继发于淋巴水肿引起的全身细胞运动紊乱。通过开发改进的调查技术，我们将能够更清楚地对患者进行分类，发现更多的基因以及这些基因如何使淋巴系统生长和工作。这可能与淋巴水肿以外的疾病有关，迄今为止，淋巴水肿可能还不知道与淋巴有关；例如，心脏病发作后心肌的恢复可能依赖于淋巴功能。发现原发性淋巴水肿的基因将揭示它们在人类生物学和病理学中的广泛作用。

Lymphoedema is swelling of any body part caused by a fault or obstruction in the lymphatic system, and is one of the most neglected areas in healthcare. Data suggest it is twice as common as type 1 diabetes (which is estimated at 400,000 in the UK) but much less recognised. Primary lymphoedema is often considered genetic in origin, whereas secondary lymphoedema has an identifiable cause such as the surgical removal of lymph glands for cancer. In the last 5 years a number of genes have been identified which, when faulty, cause inherited forms of lymphoedema. Finding the causal gene means a specific diagnosis can be made by a blood test through examination of the DNA of the patient suspected of having that particular type of lymphoedema. This helps inform the patient about their condition and what might happen to them in their lifetime. We have been studying lymphoedema for over 30 years. Genes have been discovered through investigating the DNA of patients who have as closely matched lymphoedema as it is possible to test. Detailed clinical histories and examination findings are recorded but clinical appearances alone are often not sufficient to distinguish one type of Primary Lymphoedema from another. This proposed research study is designed to provide better methods of investigation that will help distinguish one type of Primary Lymphoedema from another and give us a better insight into the mechanisms that produce the lymphoedema (and so help to design new treatments). Current tools for investigation of lymphoedema are very limited. Lymphoscintigraphy is the only widely available method within the NHS for the diagnosis of lymphoedema but it does not enable direct visualisation of the lymph vessels. Two methods are proposed to overcome this. The first is Magnetic Resonance Lymphangiography (MRL) using injected contrast, which enables distinction of lymph vessels from blood vessels. MRL will also be used to see the malformed lymph vessels inside the body. The second method of investigation is Indocyanine Green Lymphography (ICGL). This involves the injection of a dye that is seen by a camera in the near infrared spectrum wavelength of light. ICGL has been used to image lymph vessels just under the skin of an arm or leg prior to lymphatic microsurgery but has never been used to study Primary Lymphoedema. MRL will enable imaging of deeper lymph vessels whereas ICGL will provide information on lymph vessel pumping and valve function. Unlike lymphoscintigraphy neither MRL nor ICGL involve radiation. To study the smaller lymph capillaries in the skin we will perform biopsies but analyse them using a revolutionary, state of the art, 3D imaging technique. This will tell us much more about the structure and function of malfunctioning small lymphatic vessels in the patient groups. Infection can be a devastating consequence of lymphoedema because the lymph system is part of our immune system, so when the lymph system goes wrong so does immune function. We have already shown that in some genetic forms of lymphoedema, the white cells of the lymph system (lymphocytes) are low in number. There are virtually no studies in humans to explain why this is. We plan to study the numbers, trafficking and function of lymphocytes in order to understand if the immune dysfunction is a result of the genes or secondary to disturbed movement of the cells throughout the body from the lymphoedema. By developing improved investigation techniques we will be able to categorise our patients more clearly and discover more genes and how those genes make the lymph system grow and work. This may have relevance to diseases other than lymphoedema, which hitherto may not have been known to have a lymphatic contribution; for example the recovery of cardiac muscle after a heart attack may be dependent on lymphatic function. Discovering genes in primary lymphoedema will inform on their wide-ranging roles in human biology and pathology.