# Hereditary lymphedema
Hereditary (primary) lymphedema is a group of genetic disorders in which the lymphatic vessels develop abnormally or function poorly, so that protein-rich lymph fluid accumulates in tissues and causes swelling, most often of the legs.[1](https://www.nature.com/articles/s41572-021-00309-7) It can be present at birth or appear later in childhood, adolescence, or adulthood, and it can occur in isolation or as part of a wider syndrome.[1](https://www.nature.com/articles/s41572-021-00309-7) Older classifications divided primary lymphedema by age of onset into congenital lymphedema (present by age 2), lymphedema praecox (onset ages 2 to 35), and lymphedema tarda (after 35); modern classifications instead combine onset age with the lymphatic imaging findings and the underlying gene.[2](https://rarediseases.org/rare-diseases/hereditary-lymphedema/) In one classified cohort, congenital-onset and late-onset disease occurred in a ratio of about 1:4, with the highest incidence in adolescence, and late-onset disease was more common in females (sex ratio 1.5:1 versus 1.04:1 for congenital onset).[3](https://doi.org/10.2458/lymph.6175)
| Key fact | Detail |
|---|---|
| Definition | Genetic developmental or functional lymphatic disease causing lymph accumulation and swelling, isolated or syndromic[1](https://www.nature.com/articles/s41572-021-00309-7) |
| Recognized subtype | Milroy disease, one of the more common causes of primary lymphedema, caused by FLT4 (VEGFR3) variants; variants may arise de novo[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC7525776/) • [5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) |
| Penetrance in Milroy | 85%-90% of FLT4 variant carriers develop lower-limb lymphedema by age three; 10%-15% remain unaffected[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) |
| Diagnostic sign for LDS | Distichiasis (extra eyelashes) in 94% of affected individuals[6](https://www.ncbi.nlm.nih.gov/books/NBK1457/) |
| Molecular diagnosis rate | About one-third of primary lymphoedema patients overall; 36% of familial and 8% of sporadic cases in a screened cohort[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC3776465/) • [1](https://www.nature.com/articles/s41572-021-00309-7) |
| Inheritance | Autosomal dominant in Milroy and lymphedema-distichiasis; 50% recurrence risk; ~10% (Milroy) and ~25% (LDS) de novo[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) • [6](https://www.ncbi.nlm.nih.gov/books/NBK1457/) • [2](https://rarediseases.org/rare-diseases/hereditary-lymphedema/) |
| Mainstay treatment | Compression therapy with manual drainage, exercise, and compressive garments; surgery for carefully selected cases[1](https://www.nature.com/articles/s41572-021-00309-7) |
## Genetic causes and mechanisms
**Milroy disease** results from heterozygous pathogenic variants in [FLT4](https://www.edgepedia.org/flt4), the gene encoding the vascular endothelial growth factor receptor 3 (VEGFR3), a tyrosine kinase receptor required for lymphatic development. Most variants are missense variants in the tyrosine kinase domain of the gene.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) These mutations lead to the development of small or absent lymphatic vessels, so lymph fluid is not transported properly and builds up in tissues; how the same mutations produce the disorder's non-edema features, such as toenail changes, is unknown.[8](https://medlineplus.gov/genetics/condition/milroy-disease/) On lymphoscintigraphy (imaging test tracing lymph flow with injected radioactive colloid) this pattern appears as a lack of uptake of radioactive colloid in the ilioinguinal lymph nodes, described as functional aplasia: the lymphatic vessels present are too rudimentary to transport the tracer.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/)
**Lymphedema-distichiasis syndrome (LDS)** is caused by pathogenic variants in FOXC2, a transcription factor gene that plays an essential role in regulating lymphatic valve development.[2](https://rarediseases.org/rare-diseases/hereditary-lymphedema/) Valve failure rather than vessel aplasia fits the clinical picture: lymphatic vessels form, but backflow develops, and swelling typically appears later than in Milroy, around puberty, often asymmetrically.[6](https://www.ncbi.nlm.nih.gov/books/NBK1457/)
Rarer causes of primary lymphedema include GJC2, SOX18, GATA2, CCBE1, PTPN14, and CELSR1; in a whole-exome sequencing cohort, every non-FLT4 pathogenic variant found was loss-of-function, and the cohort contained 22 FLT4 and 8 FOXC2 variants among 38 variants in 37 of 211 tested patients (18%).[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC3776465/) • [3](https://doi.org/10.2458/lymph.6175) Familial primary lymphedema commonly segregates in an autosomal dominant pattern, with recessive inheritance also seen.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC3776465/)
## Clinical features: Milroy disease and lymphedema-distichiasis
[Milroy disease](https://www.edgepedia.org/milroy-disease) presents at birth or in infancy with lower-limb lymphedema, typically involving the feet. Associated findings include hydrocele in 37% of affected males, [prominent veins](https://www.edgepedia.org/prominent-veins) below the knees in 23%, upslanting toenails in 14%, papillomatosis in 10%, and urethral abnormalities in males in 4%.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) About 85%-90% of FLT4 variant carriers develop bilateral lower-limb edema in early childhood; the GeneReviews reference places this by age three.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) Edema can improve, particularly during the early years, so congenital swelling does not automatically mean lifelong severe disease.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/)
[Lymphedema-distichiasis syndrome](https://www.edgepedia.org/lymphedema-distichiasis-syndrome) differs from Milroy in onset and in its signature sign. Its defining feature is distichiasis: extra eyelashes that grow from the meibomian glands, an anomaly that may be present at birth and is observed in 94% of affected individuals.[6](https://www.ncbi.nlm.nih.gov/books/NBK1457/) Distichiasis matters diagnostically because the lymphedema itself usually starts in late childhood or puberty and may be asymmetric, so an extra row of lashes in a young person with leg swelling points strongly to FOXC2 testing. About 75% of affected individuals have ocular findings, including corneal irritation, recurrent conjunctivitis, and photophobia, caused by the lashes abrading the eye.[6](https://www.ncbi.nlm.nih.gov/books/NBK1457/) Approximately 80% of individuals have lymphedema by early adulthood (age 30), although a few develop it later.[6](https://www.ncbi.nlm.nih.gov/books/NBK1457/) Males tend to develop edema earlier and experience more cellulitis than females.[6](https://www.ncbi.nlm.nih.gov/books/NBK1457/) LDS is also associated with cleft palate, ptosis, corneal abnormalities, cardiac defects, and early-onset varicose veins.[2](https://rarediseases.org/rare-diseases/hereditary-lymphedema/)
## Diagnosis, genetic testing, and mimics
The diagnosis of Milroy disease is established in a person with congenital or infantile-onset lower-limb lymphedema accompanied by lack of radioactive colloid uptake in the ilioinguinal lymph nodes on lymphoscintigraphy and/or identification of a heterozygous FLT4 pathogenic variant. Testing may be single-gene, a multigene panel, or comprehensive genomic testing.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) In LDS, a heterozygous FOXC2 pathogenic variant can confirm the diagnosis when clinical findings are not by themselves diagnostic.[6](https://www.ncbi.nlm.nih.gov/books/NBK1457/) A practical diagnostic framework divides congenital non-syndromic hereditary lymphedema into Milroy lymphedema (HL1A), Milroy-like lymphedema (HL1D), and hereditary lymphedema 1B (HL1B).[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC10412090/)
**Mimics to exclude.** [Turner syndrome](https://www.edgepedia.org/turner-syndrome), affecting about 1 in 2,500 to 1 in 3,000 live female births, should be considered in females with congenital lymphedema affecting the hands and feet.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) [Klippel-Trénaunay syndrome](https://www.edgepedia.org/klippel-trenaunay-syndrome) and Parkes-Weber syndrome are vascular malformation conditions that include lymphatic anomalies together with [limb overgrowth](https://www.edgepedia.org/limb-overgrowth), distinguishing them from isolated hereditary lymphedema.[2](https://rarediseases.org/rare-diseases/hereditary-lymphedema/) In known FLT4 families, prenatal ultrasonography may detect swelling of the dorsum of the feet and mild pleural effusions that often resolve; once the familial variant is identified, prenatal and preimplantation genetic testing are possible.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/)
## Inheritance and penetrance
Both major conditions are autosomal dominant. Each child of an affected individual has a 50% chance of inheriting the variant, and the sibling recurrence risk is 50% when a parent carries the variant.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) • [6](https://www.ncbi.nlm.nih.gov/books/NBK1457/) De novo variants account for a minority of cases: approximately 10% in Milroy disease[2](https://rarediseases.org/rare-diseases/hereditary-lymphedema/) and about 25% in LDS, where roughly 75% of affected individuals have an affected parent.[6](https://www.ncbi.nlm.nih.gov/books/NBK1457/)
Penetrance in Milroy is high but incomplete. Conversely to the 85%-90% who develop edema by age three, 10%-15% of individuals with an FLT4 pathogenic variant are clinically unaffected, with noticeable variability within families.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) Because de novo variants occur, a family history is not essential for the diagnosis of Milroy disease.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC7525776/)
## Management and complications
Management aims at reducing or preventing swelling with compression therapy, combining manual lymphatic drainage, exercise, and compressive garments; various surgical techniques are reserved for carefully selected cases.[1](https://www.nature.com/articles/s41572-021-00309-7)
Cellulitis, a bacterial infection of the swollen limb, occurs in approximately 20% of individuals with Milroy disease, and is significantly more likely in males; the same sex difference is reported in LDS.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/) • [6](https://www.ncbi.nlm.nih.gov/books/NBK1457/)
Long-standing primary lymphedema also carries a risk of [Stewart-Treves syndrome](https://www.edgepedia.org/stewart-treves-syndrome), a lymphangiosarcoma arising in the lymphedematous extremity that can spread to the adjacent trunk and lungs.[2](https://rarediseases.org/rare-diseases/hereditary-lymphedema/)
## Research directions
The most concrete translational result comes from the VEGF-C pathway that FLT4 mutations disrupt. Attempts at overexpressing VEGF-C, the ligand for FLT4, have been successful in producing functional lymphatics in mice, and this growth-factor approach, combined with lymph node transfer, is now being studied in humans in a clinical trial for breast-cancer-related secondary lymphedema.[5](https://www.ncbi.nlm.nih.gov/books/NBK1239/)
## References
1. [Primary lymphoedema | Nature Reviews Disease Primers](https://www.nature.com/articles/s41572-021-00309-7)
2. [Primary Lymphedema - NORD](https://rarediseases.org/rare-diseases/hereditary-lymphedema/)
3. [An updated classification of primary lymphedema based on age of onset, lymphatic anomalies, and genetics](https://doi.org/10.2458/lymph.6175)
4. [Update and audit of the St George's classification algorithm of primary lymphatic anomalies](https://pmc.ncbi.nlm.nih.gov/articles/PMC7525776/)
5. [Milroy Disease - GeneReviews® - NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK1239/)
6. [Lymphedema-Distichiasis Syndrome - GeneReviews® - NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK1457/)
7. [Mutations in the VEGFR3 Signaling Pathway Explain 36% of Familial Lymphedema](https://pmc.ncbi.nlm.nih.gov/articles/PMC3776465/)
8. [Milroy disease: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/milroy-disease/)
9. [A Practical Approach to the Diagnosis of Lymphedema: A Narrative Review](https://pmc.ncbi.nlm.nih.gov/articles/PMC10412090/)
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*Topic: Encyclopedia › Life and health › Human health and medicine › Human structure and function › Cardiovascular and lymphatic systems › Lymphatic system › Lymphatic disorders › Lymphatic malformations and other lymphatic disease › Syndromic and congenital lymphatic malformations*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026 · Edited: Sep 30, 2026; Oct 11, 2026 · Last review: Sep 30, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license