Research Perspectives in Inherited Lymphatic Disease

Pathophysiology, Diagnosis, and Management of Canine Intestinal Lymphangiectasia: A Comparative Review

Intestinal lymphangiectasia was first described in the dog over 50 years ago. Despite this, canine IL remains poorly understood and challenging to manage. Intestinal lymphangiectasia is characterized by variable intestinal lymphatic dilation, lymphatic obstruction, and/or lymphangitis, and is a common cause of protein-losing enteropathy in the dog. Breed predispositions are suggestive of a genetic cause, but IL can also occur as a secondary process. Similarly, both primary and secondary IL have been described in humans. Intestinal lymphangiectasia is definitively diagnosed via intestinal histopathology, but other diagnostic results can be suggestive of IL. Advanced imaging techniques are frequently utilized to aid in the diagnosis of IL in humans but have not been thoroughly investigated in the dog. Management strategies differ between humans and dogs. Dietary modification is the mainstay of therapy in humans with additional pharmacological therapies occasionally employed, and immunosuppressives are rarely used due to the lack of a recognized immune pathogenesis. In contrast, corticosteroid and immunosuppressive therapies are more commonly utilized in canine IL. This review aims toward a better understanding of canine IL with an emphasis on recent discoveries, comparative aspects, and necessary future investigations.

A novel mutation in the conserved sequence of vascular endothelial growth factor receptor 3 leads to primary lymphoedema

Objective

To investigate whether lymphoedema in a Chinese family showed the hereditary and clinical characteristics of Milroy disease, an autosomal dominant form of congenital lymphoedema, typically characterized by chronic lower limb tissue swelling due to abnormal lymphatic vasculature development, and to perform mutational analyses of vascular endothelial growth factor receptor (VEGFR)3.

Methods

Individuals from a three-generation family affected by congenital lymphoedema were clinically assessed for Milroy disease. Mutation analysis of VEGFR3 was performed using DNA from family members and healthy controls.

Results

Out of 20 family members, eight were diagnosed with hereditary lymphoedema. Mutation analyses revealed a novel mutation site for c.3163 G>A, resulting in a p.1055D>N mutation in the second tyrosine kinase domain of VEGFR3, which was present in affected individuals only (absent in all unaffected family members and 130 healthy controls). Computed functional analyses showed the mutation may lead to structural alterations with a probability of 0.99999 of being disease causing.

Conclusion

A novel mutation associated with Milroy disease was identified in a Chinese family, expanding our knowledge of VEGFR3 gene function and providing a potential molecular target for treating hereditary lymphoedema.

Vascular endothelial growth factor (VEGF) levels in short, GH treated children: a distinct pattern of VEGF-C in Noonan syndrome

CONTEXT

Noonan syndrome (NS) is characterized by short stature and elevated risk of lymphedema. The mechanism underlying lymphedema may be mediated by vascular endothelial growth factors (VEGFs).

OBJECTIVE

To assess the effect of growth hormone (GH) treatment on plasma insulin-like growth factor (IGF)-1, VEGF-A and VEGF-C levels in patients with NS as compared to short GH-sufficient children.

DESIGN

Retrospective, comparative.

SETTING

Endocrinology department of a tertiary pediatric medical center.

PATIENTS AND METHODS

Plasma IGF-1, VEGF-A and VEGF-C levels were measured before and during GH treatment in 6 patients with NS and 18 age-matched short subjects (Turner, idiopathic short stature and small for gestational age).

MAIN OUTCOME MEASURES

Changes in plasma VEGF and IGF-1 levels.

RESULTS

Baseline IGF-1 SDS levels were slightly lower in NS patients compared with controls; IGF-1 response to GH therapy was markedly lower in NS patients compared with controls (p = 0.017). Mean baseline VEGF-A levels were similar in NS patients and controls whilst mean baseline VEGF-C levels were significantly lower in the NS group as compared with controls (p = 0.022). Plasma VEGF-A and VEGF-C levels did not significantly change during GH treatment in the study cohort. No correlation was found between VEGF-C levels and levels of IGF-1, VEGF-A and auxological parameters, either before or during GH administration.

CONCLUSION

Children with NS have a distinct growth factor profile including low basal VEGF-C and flattened IGF-1 response to GH. Further studies are needed to confirm our findings and to elucidate the interaction between VEGF-C levels and lymphedema.

Possible genetic predisposition to lymphedema after breast cancer

BACKGROUND

Known risk factors for secondary lymphedema only partially explain who develops lymphedema following cancer, suggesting that inherited genetic susceptibility may influence risk. Moreover, identification of molecular signatures could facilitate lymphedema risk prediction prior to surgery or lead to effective drug therapies for prevention or treatment. Recent advances in the molecular biology underlying development of the lymphatic system and related congenital disorders implicate a number of potential candidate genes to explore in relation to secondary lymphedema.

METHODS AND RESULTS

We undertook a nested case-control study, with participants who had developed lymphedema after surgical intervention within the first 18 months of their breast cancer diagnosis serving as cases (n=22) and those without lymphedema serving as controls (n=98), identified from a prospective, population-based, cohort study in Queensland, Australia. TagSNPs that covered all known genetic variation in the genes SOX18, VEGFC, VEGFD, VEGFR2, VEGFR3, RORC, FOXC2, LYVE1, ADM, and PROX1 were selected for genotyping. Multiple SNPs within three receptor genes, VEGFR2, VEGFR3, and RORC, were associated with lymphedema defined by statistical significance (p<0.05) or extreme risk estimates (OR <0.5 or >2.0).

CONCLUSIONS

These provocative, albeit preliminary, findings regarding possible genetic predisposition to secondary lymphedema following breast cancer treatment warrant further attention for potential replication using larger datasets.

Gastrointestinal lymphatics in health and disease

Lymphatics perform essential transport and immune regulatory functions to maintain homeostasis in the gastrointestinal (GI) system. Although blood and lymphatic vessels function as parallel and integrated systems, our understanding of lymphatic structure, regulation and functioning lags far behind that of the blood vascular system. This chapter reviews lymphatic flow, differences in lymphangiogenic and hemangiogenic factors, lymphatic fate determinants and structural features, and examines how altered molecular signaling influences lymphatic function in organs of the GI system. Innate errors in lymphatic development frequently disturb GI functioning and physiology. Expansion of lymphatics, a prominent feature of GI inflammation, may also play an important role in tissue restitution following injury. Destruction or dysregulation of lymphatics, following injury, surgery or chronic inflammation also exacerbates GI disease activity. Understanding the physiological roles played by GI lymphatics is essential to elucidating their underlying contributions to forms of congenital and acquired forms of GI pathology, and will provide novel approaches for therapy.

Lymphedema beyond breast cancer: a systematic review and meta-analysis of cancer-related secondary lymphedema

BACKGROUND

Secondary lymphedema is a debilitating, chronic, progressive condition that commonly occurs after the treatment of breast cancer. The purpose of the current study was to perform a systematic review and meta-analysis of the oncology-related literature excluding breast cancer to derive estimates of lymphedema incidence and to identify potential risk factors among various malignancies.

METHODS

The authors systematically reviewed 3 major medical indices (MEDLINE, Cochrane Library databases, and Scopus) to identify studies (1972-2008) that included a prospective assessment of lymphedema after cancer treatment. Studies were categorized according to malignancy, and data included treatment, complications, lymphedema measurement criteria, lymphedema incidence, and follow-up interval. A quality assessment of individual studies was performed using established criteria for systematic reviews. Bayesian meta-analytic techniques were applied to derive summary estimates when sufficient data were available.

RESULTS

A total of 47 studies (7779 cancer survivors) met inclusion criteria: melanoma (n = 15), gynecologic malignancies (n = 22), genitourinary cancers (n = 8), head/neck cancers (n = 1), and sarcomas (n = 1). The overall incidence of lymphedema was 15.5% and varied by malignancy (P < .001): melanoma, 16% (upper extremity, 5%; lower extremity, 28%); gynecologic, 20%; genitourinary, 10%; head/neck, 4%; and sarcoma, 30%. Increased lymphedema risk was also noted for patients undergoing pelvic dissections (22%) and radiation therapy (31%). Objective measurement methods and longer follow-up were both associated with increased lymphedema incidence.

CONCLUSIONS

Lymphedema is a common condition affecting cancer survivors with various malignancies. The incidence of lymphedema is related to the type and extent of treatment, anatomic location, heterogeneity of assessment methods, and length of follow-up.

Warty skin changes, chronic scrotal lymphoedema, and facial dysmorphism

We present the case of a 49-year-old Caucasian man whose main complaints were wart-like skin changes and scrotal lymphoedema. Furthermore, our patient showed signs of a common hereditary disease: lymphoedema, short stature, webbed neck, low frontal and posterior hairline, downslanting palpebral fissures, pale blue iris, broad nose, flat philtrum, and prominent nasolabial folds. His ears were low set and retroverted with a thick helix. However, no diagnosis was made for 49 years. The interdisciplinary dialogue of various specialists to make the final diagnosis is presented and discussed.