Pathogenic variants in HGF give rise to childhood-to-late onset primary lymphoedema by loss of function.

Developmental and functional defects in the lymphatic system are responsible for primary lymphoedema (PL). PL is a chronic debilitating disease caused by increased accumulation of interstitial fluid, predisposing to inflammation, infections and fibrosis. There is no cure, only symptomatic treatment is available. Thirty-two genes or loci have been linked to PL, and another 22 are suggested, including Hepatocyte Growth Factor (HGF). We searched for HGF variants in 770 index patients from the Brussels PL cohort. We identified ten variants predicted to cause HGF loss-of-function (six nonsense, two frameshifts, and two splice-site changes; 1.3% of our cohort), and 14 missense variants predicted to be pathogenic in 17 families (2.21%). We studied co-segregation within families, mRNA stability for non-sense variants, and in vitro functional effects of the missense variants. Analyses of the mRNA of patient cells revealed degradation of the nonsense mutant allele. Reduced protein secretion was detected for nine of the 14 missense variants expressed in COS-7 cells. Stimulation of lymphatic endothelial cells with these 14 HGF variant proteins resulted in decreased activation of the downstream targets AKT and ERK1/2 for three of them. Clinically, HGF-associated PL was diverse, but predominantly bilateral in the lower limbs with onset varying from early childhood to adulthood. Finally, aggregation study in a second independent cohort underscored that rare likely pathogenic variants in HGF explain about 2% of PL. Therefore, HGF signalling seems crucial for lymphatic development and/or maintenance in human beings and HGF should be included in diagnostic genetic screens for PL.

Factors associated with cellulitis in lymphoedema of the arm - an international cross-sectional study (LIMPRINT).

BACKGROUND: Lymphoedema is a globally neglected health care problem and a common complication following breast cancer treatment. Lymphoedema is a well-known predisposing factor for cellulitis, but few have investigated the risk factors for cellulitis in this patient cohort on an international level. The aim of this study was to identify the frequency of cellulitis in patients with lymphoedema of the arm, including potential risk factors for cellulitis. METHODS: An international, multi-centre, cross-sectional study including patients with clinically assessed arm lymphoedema. The primary outcome was the incidence of cellulitis located to the arm with lymphoedema within the last 12 months, and its potential associated risk factors. The secondary outcome was life-time prevalence of cellulitis. Adults with clinically-assessed arm lymphoedema/chronic oedema (all causes) and able to give informed consent were included. End-of-life-patients or those judged as not in the patient's best interest were excluded. Both univariable and multivariable analysis were performed. RESULTS: A total of 2160 patients were included from Australia, Denmark, France, Ireland, Italy, Japan, Turkey and United Kingdom. Secondary lymphoedema was present in 98% of the patients; 95% of these were judged as related to cancer or its treatment. The lifetime prevalence of cellulitis was 22% and 1-year incidence 11%. Following multivariable analysis, factors associated with recent cellulitis were longer swelling duration and having poorly controlled lymphoedema. Compared to having lymphoedema less than 1 year, the risk increased with duration: 1-2 years (OR 2.15), 2-5 years (OR 2.86), 5-10 years (OR 3.15). Patients with well-controlled lymphoedema had a 46% lower risk of cellulitis (OR 0.54, 95% CI 0.39-0.73, p < 0.001). More advanced stages of lymphoedema were associated with cellulitis even after adjustment for swelling duration and control of swelling by logistic regression (stage II OR 5.44, stage III OR 9.13, p = 0.002), demonstrated in a subgroup analysis. CONCLUSION: Patients with advanced arm lymphoedema are at particular risk of developing cellulitis. Prevention of lymphoedema progression is crucial. The results lend towards a positive effect of having well-treated lymphoedema on the frequency of cellulitis.

Positive Impact of a New Compressive Garment in Patients with Genital Lymphedema: OLYMPY Study.

Purpose: Genital lymphedema is a chronic debilitating condition associated with highly impaired health-related quality of life (QoL). This prospective multicenter study evaluated the use of a new compressive garment in patients with secondary and primary genital lymphedema. Methods: Thirty-two patients prospectively enrolled were advised to wear the compressive garment for 12 weeks (day and night). The primary endpoint was change in patient-reported QoL at 12 weeks via the patient global impression of change (PGI-C) instrument. Secondary outcomes included change in other QoL measures at 12 weeks (visual analog scale, Lymphedema Quality of Life Inventory [LyQLI], and EQ-5D questionnaires), lymphedema severity (genital lymphedema score [GLS]), and physician assessment (Clinical Global Impression-Improvement [CGI-I]). Safety and tolerability were also assessed. Results: After 12 weeks, improvement was reported in 78.6% of patients (PGI-C). Physician assessment (CGI-I) indicated clinical improvement in 82.8% of patients. Patient assessment of lymphedema symptoms showed a significant decrease in discomfort (p = 0.02) and swelling (p = 0.01). Significant declines in the mean global GLS (p < 0.0001), and in the proportion of patients reporting heaviness, tightness, swelling, or urinary dysfunction (p < 0.05 for all), were also observed. LyQLI scores decreased (indicating improved QoL) in each of the physical, psychosocial (p = 0.05), and practical domains. The compressive garment was well tolerated with high compliance, and adverse events (due to swelling or discomfort) led to permanent discontinuation in only three patients. Conclusion: The use of a new genital compression garment over 12 weeks improves the QoL and clinical measures in patients with genital lymphedema (ClinicalTrials.gov ID: NCT04602559; Registration: October 20, 2020).

LYMPHOSCORE (Lymphoscintigraphy Scoring Reliability) Reliability of a New Qualitative and Semiquantitative Lymphoscintigraphy Scoring System for Primary Lymphedema.

PURPOSE OF THE REPORT: Primary lymphedema (PLE) is a rare chronic disorder. Extremity lymphoscintigraphy offers access for dynamic and functional information on peripheral lymphatics and lymph nodes. We aimed to assess intraobserver and interobserver reliability of a new lymphoscintigraphy quantitative and qualitative scoring system in a homogeneous population of adult patients followed for PLE of the lower limb(s). PATIENTS AND METHODS: This is a monocentric retrospective study. Clinical files of patients who underwent a lymphoscintigraphy were reviewed for inclusion. Lymphoscintigraphies were interpreted twice by 2 observers with a washout period. To assess intraobserver and interobserver reliability for both lower limbs, Cohen κ and Gwet's AC1 reliability coefficients were calculated with 95% confidence interval and P value of the zero-reliability comparison test. To interpret reliability coefficients, we used the orders of magnitude reported by Landis and Koch. RESULTS: One hundred forty-four patients (288 limbs) with PLE were included. For intraobserver reliability, agreement range was 0.87-1 with an almost perfect agreement in all staging items of the score for both limbs with the lower limit of the 95% confidence interval ≥80%. Interobserver reliability was overall strong or almost perfect, ranging from 0.67 to 0.97. CONCLUSIONS: This new scoring system demonstrated excellent intraobserver reliability and a very good interobserver reliability. Lymphoscintigraphy, when performed in a referral center and interpreted by trained nuclear medicine physicians, is a reliable means of investigation in patients with PLE of the lower limbs. This reproducibility advocates for further use of lymphoscintigraphy in multicentric cohorts of PLE patients.

Loss-of-function mutations of the TIE1 receptor tyrosine kinase cause late-onset primary lymphedema.

Primary lymphedema (PL), characterized by tissue swelling, fat accumulation, and fibrosis, results from defects in lymphatic vessels or valves caused by mutations in genes involved in development, maturation, and function of the lymphatic vascular system. Pathogenic variants in various genes have been identified in about 30% of PL cases. By screening of a cohort of 755 individuals with PL, we identified two TIE1 (tyrosine kinase with immunoglobulin- and epidermal growth factor-like domains 1) missense variants and one truncating variant, all predicted to be pathogenic by bioinformatic algorithms. The TIE1 receptor, in complex with TIE2, binds angiopoietins to regulate the formation and remodeling of blood and lymphatic vessels. The premature stop codon mutant encoded an inactive truncated extracellular TIE1 fragment with decreased mRNA stability, and the amino acid substitutions led to decreased TIE1 signaling activity. By reproducing the two missense variants in mouse Tie1 via CRISPR/Cas9, we showed that both cause edema and are lethal in homozygous mice. Thus, our results indicate that TIE1 loss-of-function variants can cause lymphatic dysfunction in patients. Together with our earlier demonstration that ANGPT2 loss-of-function mutations can also cause PL, our results emphasize the important role of the ANGPT2/TIE1 pathway in lymphatic function.