Arteriovenous malformation Map2k1 mutation affects vasculogenesis.

Somatic activating MAP2K1 mutations in endothelial cells (ECs) cause extracranial arteriovenous malformation (AVM). We previously reported the generation of a mouse line allowing inducible expression of constitutively active MAP2K1 (p.K57N) from the Rosa locus (R26GT-Map2k1-GFP/+) and showed, using Tg-Cdh5CreER, that EC expression of mutant MAP2K1 is sufficient for the development of vascular malformations in the brain, ear, and intestines. To gain further insight into the mechanism by which mutant MAP2K1 drives AVM development, we induced MAP2K1 (p.K57N) expression in ECs of postnatal-day-1 pups (P1) and investigated the changes in gene expression in P9 brain ECs by RNA-seq. We found that over-expression of MAP2K1 altered the transcript abundance of > 1600 genes. Several genes had > 20-fold changes between MAP2K1 expressing and wild-type ECs; the highest were Col15a1 (39-fold) and Itgb3 (24-fold). Increased expression of COL15A1 in R26GT-Map2k1-GFP/+; Tg-Cdh5CreER+/- brain ECs was validated by immunostaining. Ontology showed that differentially expressed genes were involved in processes important for vasculogenesis (e.g., cell migration, adhesion, extracellular matrix organization, tube formation, angiogenesis). Understanding how these genes and pathways contribute to AVM formation will help identify targets for therapeutic intervention.

Delayed Cardiac Metastasis from Renal Cell Carcinoma Caused by VHL Mutation.

Cardiac metastasis caused by renal cell carcinoma (RCC) without vena caval involvement is rare. No mutation has been associated with this unique phenotype. A 77-year-old male presented to our clinic with a symptomatic right ventricular mass after nephrectomy for clear cell RCC (ccRCC). The mass was resected, and metastatic disease was confirmed. Targeted exon sequencing identified a VHL mutation (c.494T > G, p.V165G) in the resected specimen. While more than half of ccRCC cases are associated with VHL mutations, this case is the first to show the association between delayed, isolated cardiac metastasis and VHL V165G mutation. The phenotype presented 12 years after nephrectomy and localized to the right ventricular apex. Further genomic characterization of cases with cardiac metastases may provide clues regarding unique mutations noted. Patients exhibiting delayed spread of RCC to the heart must be screened for this mutation.

Endothelial cell expression of mutant Map2k1 causes vascular malformations in mice.

Extracranial arteriovenous malformation (AVM) is a congenital vascular anomaly causing disfigurement, bleeding, ulceration, and pain. Most lesions are associated with somatic MAP2K1 activating mutations in endothelial cells (ECs). The purpose of this study was to determine if EC expression of mutant activated MAP2K1 is sufficient to produce vascular malformations in mice. We generated mice with a ROSA26 allele containing a lox-stop-lox gene trap (GT), Map2k1 cDNA with an activating p.K57N missense mutation, an internal ribosomal entry site, and green fluorescent protein cDNA (R26GT-Map2k1-GFP). We expressed mutant MAP2K1 and GFP in ECs of fetal and newborn mice using Tg-Cdh5Cre or Tg-Cdh5CreER alleles. Tg-Cdh5Cre+/-;R26GT-Map2k1-GFP/+ animals that express mutant MAP2K1 in ECs in utero developed diffuse vascular abnormalities and died by embryonic (E) day 16.5. Tg-Cdh5CreER+/-;R26GT-Map2k1-GFP/+ animals in which mutant MAP2K1 expression was induced in ECs by tamoxifen at postnatal (P) day 1 developed vascular malformations in the brain, ear, and intestines by P23. The lesions consisted of abnormal networks of blood vessels containing recombined and non-recombined ECs. In conclusion, expression of MAP2K1 p.K57N is sufficient to cause vascular malformations in mice. This model can be used to study the malformation process and for pre-clinical pharmacologic studies.

Lymphedema and Obesity.

Lymphedema results from inadequate lymphatic function. Extreme obesity can cause lower extremity lymphedema, termed "obesity-induced lymphedema (OIL)." OIL is a form of secondary lymphedema that may occur once an individual's body mass index (BMI) exceeds 40. The risk of lymphatic dysfunction increases with elevated BMI and is almost universal once BMI exceeds 60. Obesity has a negative impact on lymphatic density in subcutaneous tissue, lymphatic endothelial cell proliferation, lymphatic leakiness, collecting-vessel pumping capacity, and clearance of macromolecules. Lymphatic fluid unable to be taken up by lymphatic vessels results in increased subcutaneous adipose deposition, fibrosis, and worsening obesity. Individuals with OIL are in an unfavorable cycle of weight gain and lymphatic injury. The fundamental treatment for OIL is weight loss.

Current Overview of Obesity-Induced Lymphedema.

Significance: Obesity affects one-third of the U.S. population and lymphedema is a chronic disorder without a cure. The relationship between obesity and lymphedema has important implications for public health. Recent Advances: Extreme obesity can cause lower extremity lymphedema, termed "obesity-induced lymphedema (OIL)." OIL is a form of secondary lymphedema that may occur once an individual's body mass index (BMI) exceeds 40. The risk of lymphatic dysfunction increases with elevated BMI and is almost universal once BMI exceeds 60. Patients with OIL also may develop areas of massive localized lymphedema (MLL). Critical Issues: Individuals with OIL are in an unfavorable cycle of weight gain and lymphatic injury. As BMI increases lymphedema worsens, ambulation becomes more difficult, and BMI further rises. The fundamental treatment for OIL is weight loss. Resection of areas of MLL and lower extremity volume reduction are performed when the BMI is lowered to <40 to reduce complications and recurrence. Future Directions: The mechanisms by which obesity causes lymphedema are still being elucidated. Although lymphatic function can improve following weight loss, it is unclear whether lymphedema may be completely reversed.

Primary Lymphedema: Update on Genetic Basis and Management.

Significance: Primary lymphedema is a chronic condition without a cure. The lower extremities are more commonly affected than the arms or genitalia. The disease can be syndromic. Morbidity includes decreased self-esteem, infections, and reduced function of the area. Recent Advances: Several mutations can cause lymphedema, and new variants continue to be elucidated. A critical determinant that predicts the natural history and morbidity of lymphedema is the patient's body mass index (BMI). Individuals who maintain an active lifestyle with a normal BMI generally have less severe disease compared to subjects who are obese. Because other causes of lower extremity enlargement can be confused with lymphedema, definitive diagnosis requires lymphoscintigraphy. Critical Issues: Most patients with primary lymphedema are satisfactorily managed with compression regimens, exercise, and maintenance of a normal body weight. Suction-assisted lipectomy is our preferred operative intervention for symptomatic patients who have failed conservative therapy. Suction-assisted lipectomy effectively removes excess subcutaneous fibro-adipose tissue and can improve underlying lymphatic function. Future Directions: Many patients with primary lymphedema do not have an identifiable mutation and thus novel variants will be identified. The mechanisms by which mutations cause lymphedema continue to be studied. In the future, drug therapy for the disease may be developed.

Lymphedema and Sports: A Case Series of Athletic Patients.

Background: Lymphedema is a chronic progressive condition without a cure. Although the disease can cause significant morbidity, it is not a contraindication to participating in sports. The purpose of this study was to illustrate patients who are able to perform vigorous athletic activities to encourage individuals newly diagnosed with lymphedema. Methods and Results: Our Lymphedema Program database was reviewed for patients who performed significant sports, outside of routine exercise and fitness. Inclusion criteria were a confirmed diagnosis of lymphedema, age >16 years, and body mass index (BMI) <30. Age, gender, type of lymphedema (i.e., primary or secondary), location of disease, BMI, and athletic activities were recorded. Fourteen patients met inclusion criteria: seven males and seven females. Average age was 34 years (range 17-77) and lymphedema was primary (n = 11) or secondary (n = 3). All subjects had lower extremity disease: right leg (n = 6), left leg (n = 5), bilateral (n = 3). The average BMI was 23 (range 18-27). Sports performed by the cohort included marathon running (n = 3), soccer team (n = 2), skiing (n = 2), basketball team, rugby, swimming team, college lacrosse team, hockey team, college tennis team, and surfing. Conclusions: Patients with lower extremity lymphedema are able to engage in competitive sports and a wide range of athletic activities. Individuals typically have a normal BMI and active lifestyle. Patients with lymphedema should be encouraged to participate in athletic pursuits that they enjoy and to maintain a normal BMI.

Parkes Weber syndrome with lymphedema caused by a somatic KRAS variant.

Parkes Weber syndrome is a vascular malformation overgrowth condition typically involving the legs. Its main features are diffuse arteriovenous fistulas and enlargement of the limb. The condition has been associated with pathogenic germline variants in RASA1 and EPHB4 We report two individuals with Parkes Weber syndrome of the leg and primary lymphedema containing a somatic KRAS variant (NM_004985.5:c.35G > A; p.Gly12Asp). KRAS variants, which cause somatic intracranial and extracranial arteriovenous malformations, also result in Parkes Weber syndrome with lymphatic malformations.

Bockenheimer disease is associated with a TEK variant.

Bockenheimer disease is a venous malformation involving all tissues of an extremity. Patients have significant morbidity, and treatment is palliative. The purpose of this study was to identify the cause of Bockenheimer disease to develop pharmacotherapy for the condition. Paraffin-embedded tissue from nine individuals with Bockenheimer disease obtained during a clinically indicated operation underwent DNA extraction. Droplet digital polymerase chain reaction (ddPCR) was used to screen for variants most commonly associated with sporadic venous malformations (TEK [NM_000459.5:c.2740C > T; p.Leu914Phe], PIK3CA [NM_006218.4:c.1624G > A; p.Glu542Lys and NM_006218.4:c.3140A > G; p.His1047Arg]). ddPCR detected a TEK L914F variant in all nine patients (variant allele fraction 2%-13%). PIK3CA E542K and H1047R variants were not identified in the specimens. Sanger sequencing and restriction enzyme digestion confirmed variants identified by ddPCR. A pathogenic variant in the endothelial cell tyrosine kinase receptor TEK is associated with Bockenheimer disease. Pharmacotherapy targeting the TEK signaling pathway might benefit patients with the condition.

EPHB4 mutation causes adult and adolescent-onset primary lymphedema.

Primary lymphedema results from the anomalous development of the lymphatic system and typically presents during infancy, childhood, or adolescence. Adult-onset primary lymphedema is rare and mutations associated with this condition have not been identified. The purpose of this investigation was to search for variants that cause adult-onset primary lymphedema. We discovered an autosomal dominant EPHB4 mutation in a patient who developed unilateral leg lymphedema at age 39 years; the same mutation affected his son who presented with the disease at 14 years of age.

Lower Extremity Reconstruction in the Pediatric Population.

Indications for lower extremity reconstruction in children are unique because most result from congenital conditions (eg, constriction ring, lymphedema, syndactyly, nevi, vascular anomalies). Like adults, pediatric patients also suffer from effects following extirpation and trauma. Principles of reconstruction are based on the condition and type of deformity. The pediatric population typically has fewer comorbidities than adults that can negatively affect outcomes (eg, diabetes, peripheral vascular disease), although children can be less compliant with postoperative care. Growth, development, appearance, and postoperative compliance are variables that especially influence operative management of children.

Lipoblastoma phenotype contains a somatic PIK3CA mutation.

Lipoblastoma typically occurs in childhood and is associated with rearrangements of the PLAG1 gene. We present a patient with an isolated mass thought to be a lipoblastoma clinically, radiographically, and histologically. The lesion was diagnosed as a PIK3CA-adipose lesion after the tissue was negative for PLAG1 rearrangement and contained a somatic PIK3CA mutation (H1047R). Although PIK3CA variants are associated with PROS (PIK3CA-related overgrowth spectrum), this report illustrates a non-syndromic, lipoblastoma phenotype caused by a PIK3CA mutation.

Lower extremity lymphatic function predicted by body mass index: a lymphoscintigraphic study of obesity and lipedema.

BACKGROUND/OBJECTIVES: Patients with obesity and lipedema commonly are misdiagnosed as having lymphedema. The conditions share phenotypic overlap and can influence each other. The purpose of this study was to delineate obesity-induced lymphedema, obesity without lymphedema, and lipedema in order to improve their diagnosis and treatment. SUBJECTS/METHODS: Our Lymphedema Center database of 700 patients was searched for patients with obesity-induced lymphedema (OIL), obesity without lymphedema (OWL), and lipedema. Patient age, sex, diagnosis, cellulitis history, body mass index (BMI), and treatment were recorded. Only subjects with lymphoscintigraphic documentation of their lymphatic function were included. RESULTS: Ninety-eight patients met inclusion criteria. Subjects with abnormal lymphatic function (n = 46) had a greater BMI (65 ± 12) and cellulitis history (n = 30, 65%) compared to individuals with normal lymphatic function [(BMI 42 ± 10); (cellulitis n = 8, 15%)] (p < 0.001). Seventeen patients had a history of lipedema and two exhibited abnormal lymphatic function (BMI 45, 54). The risk of having lower extremity lymphedema was predicted by BMI: BMI < 40 (0%), 40-49 (17%), 50-59 (63%), 60-69 (86%), 70-79 (91%), ≥80 (100%). Five patients with OIL (11%) underwent resection of massive localized lymphedema (MLL) or suction-assisted lipectomy. Three individuals (18%) with lipedema were treated with suction-assisted lipectomy. CONCLUSIONS: The risk of lymphedema in patients with obesity and lipedema can be predicted by BMI; confirmation requires lymphoscintigraphy. Individuals with OIL are at risk for cellulitis and MLL. Patients with a BMI > 40 are first managed with weight loss. Excisional procedures can further reduce extremity size once BMI has been lowered.

Lower Extremity Lymphatic Function in Nonambulatory Patients with Neuromuscular Disease.

Background: Lymphedema results from inadequate lymphatic function causing swelling in subcutaneous tissues. Lymph is transported proximally through valved lymphatic channels and muscle contraction. The purpose of this study was to determine lymphatic function in nonambulatory patients with lower extremity neuromuscular disease. Methods and Results: Our Lymphedema Program database of 700 patients was reviewed for nonambulatory patients with lower extremity neuromuscular disease. Patient age, gender, disease, body mass index (BMI), and lymphoscintigram result were recorded. Eight patients were included in the study: myelomeningocele (n = 6), spinal muscle atrophy type 2 (n = 1), Charcot Marie Tooth (n = 1). Patient ages were between 15 and 36 years; five were female. BMI range for patients without swelling or a normal lymphoscintigram (n = 4) was 22-27. Four subjects with lymphatic dysfunction by lymphoscintigram all were obese (BMI 36-74; p = 0.03). Conclusions: Nonambulatory patients with lower extremity neuromuscular dysfunction and swelling can exhibit normal lymphatic function. Obesity is associated with abnormal lymphoscintigram result and lymphedema in this patient population. Individuals should be advised to maintain a normal BMI.

Lymphedema (Seminars in pediatric surgery).

Lymphedema is the chronic, progressive swelling of tissue due to inadequate lymphatic function. Over time, protein-rich fluid accumulates in the tissue causing it to enlarge. Lymphedema is a specific disease and should not be used as a generic term for an enlarged extremity. The diagnosis is made by history and physical examination, and confirmed with lymphoscintigraphy. Intervention includes patient education, compression, and rarely, surgery. Patients are advised to exercise, maintain a normal body mass index, and moisturize / protect the diseased limb from incidental trauma. Conservative management consists of compression regimens. Operative interventions either attempt to address the underlying lymphatic anomaly or the excess tissue. Lymphatic-venous anastomosis and lymph node transfer attempt to create new lymphatic connections to improve lymph flow. Suction-assisted lipectomy and cutaneous excision reduce the size of the area by removing fibroadipose hypertrophy.

Arteriovenous malformation phenotype resembling congenital hemangioma contains KRAS mutations.

Extracranial arteriovenous malformation (AVM) is most commonly caused by a somatic mutation in MAP2K1. We report two patients with vascular anomalies that had an unclear clinical diagnosis most consistent with either an AVM or congenital hemangioma. Lesions were cutaneous, reddish-purple with telangiectasias, present at birth, and had defined borders. Histopathology indicated AVM and both lesions contained somatic KRAS mutations. A rare AVM phenotype exists that shares clinical features with congenital hemangioma.

Endothelial MAP2K1 mutations in arteriovenous malformation activate the RAS/MAPK pathway.

Arteriovenous malformation (AVM) is a locally destructive congenital vascular anomaly caused by somatic mutations in MAP2K1. The mutation is isolated to endothelial cells (ECs). The purpose of this study was to determine the effects of mutant MAP2K1 on EC signaling and vascular network formation. Pathway effects were studied using both mutant MAP2K1 (K57N) human AVM tissue and human umbilical vein endothelial cells (HUVECs) engineered to overexpress the MAP2K1 (K57N) mutation. Western blot was used to determine cell signaling along the RAS/MAPK pathway. Geltrex tube formation assays were performed to assess EC vascular network formation. Cells were treated with a MAP2K1 inhibitor (Trametinib) to determine its effect on signaling and vascular tube formation. Human mutant MAP2K1-AVM ECs had similar baseline MEK1 and ERK1/2 expression with controls; however, mutant MAP2K1-AVM ECs produced significantly more phosphorylated ERK1/2 than wild-type ECs. Mutant MAP2K1 HUVECs demonstrated significantly more phosphorylated ERK1/2 than control HUVECs. Trametinib reduced the phosphorylation of ERK1/2 in mutant cells and prevented the ability of ECs to form vascular networks. AVM MAP2K1 mutations activate RAS/MAPK signaling in ECs. ERK activation and vascular network formation are reduced with Trametinib. Pharmacotherapy using MAP2K1 inhibitors may prevent the formation or progression of AVMs.

Study of 700 Referrals to a Lymphedema Program.

Background: Lymphedema results from inadequate lymphatic function due to failure of lymphatic development or injury to a functioning lymphatic system. Patients suffer enlargement of the affected area, psychosocial morbidity, infection, and functional disability. The purpose of this study was to characterize the disease in a cohort of patients referred to a specialized center. Methods and Results: Our Lymphedema Program database was reviewed for all referrals between 2009 and 2019. Diagnosis was determined based on history, physical examination, and lymphoscintigraphy. Lymphedema type (primary, secondary, and obesity-induced), location of swelling, morbidity, previous management, accuracy of referral diagnosis, the geographic origin of the patients, and treatment in our center were analyzed. Seven hundred patients were referred with a diagnosis of "lymphedema"; 71% were female and 38% were children. Lymphedema was confirmed in 71% of the cohort: primary (62%), secondary (22%), and obesity-induced (16%). Twenty-nine percent of individuals labeled with "lymphedema" had another condition. One-half of patients had not received treatment, and 36% resided outside of our local referral area. One-third of subjects with lymphedema had an infection and 30% had >1 visit to the center. Patients with confirmed lymphedema were managed with compression stockings (100%), pneumatic compression (69%), and/or an excisional procedure (6%). Conclusions: Patients with lymphedema typically are adequately managed with conservative compression therapies and rarely require excisional operations. Diagnostic confusion is common and individuals with possible lymphedema are best managed by physicians focused on the disease.

Elevation of Costal Cartilage Ear Construct for Microtia Using a V-Y Scalp Flap.

Autologous ear construction for microtia creates an auricle using a costal cartilage framework. To separate the construct from the mastoid, the most common methods incorporate the use of fascial flaps or skin grafting. The authors describe a V-Y skin and subcutaneous scalp advancement flap for ear elevation as part of autologous ear construction for microtia. The method is simple and reliable and offers advantages compared to other techniques.