Lymphedema

Basics

DESCRIPTION

Lymphedema is a chronic progressive swelling in subcutaneous tissues, typically in an extremity or the genitals, due to protein-rich accumulation of interstitial fluid from disruption of the lymphatic system. It can be of primary or secondary origin.
Primary lymphedema has three forms, all of which stem from a developmental abnormality of lymphatic flow. Not all primary lymphedemas are clinically evident at birth.
- Congenital lymphedema, due to anomalous development of lymph system
  - Present at birth
  - Lower to upper extremity ratio: 3:1
  - 2/3 of cases are bilateral.
  - May improve with age
- Lymphedema praecox (65–80% of primary lymphedema)
  - Usually becomes evident at puberty but may appear between infancy and age 35 years
  - 70% unilateral lower extremity (L > R)
- Lymphedema tarda: presents at age 35 years or older
Secondary lymphedema is from an acquired abnormality of lymphatic flow, an injury to the lymphatic system.
- Common causes in children include the following:
  - Postsurgical obstruction
  - Burns
  - Insect bites
  - Infection
  - Scar tissue from radiation
  - Neoplasm
  - Trauma
Classification: There are several systems for grading the severity of lymphedema.
- The International Society of Lymphology (ISL) describes lymphedema using skin consistency and outcome.
  - Stage 0: dormant condition where a patient might describe their extremity as heavy
  - Stage I (mild): soft tissue that may pit, no dermal fibrosis; improves with elevation of extremity
  - Stage II (moderate): evolving dermal fibrosis that does not pit; no improvement with limb elevation
  - Stage III (severe): Tissue is swollen and thick; there may be peeling, discoloration, or trophic changes.
- The American Physical Therapy Association (APTA) describes lymphedema by measurement between the affected and unaffected extremity.
  - Mild: girth difference <3 cm
  - Moderate: girth difference of 3 to 5 cm
  - Severe: girth difference of >5 cm

EPIDEMIOLOGY

Most lymphedemas in childhood are primary (or idiopathic) lymphedema (96%).
Congenital lymphedema comprises 10–25% of primary lymphedema cases; lymphedema praecox, 65–80%; and lymphedema tarda, 10%.
Affected males—most likely congenital and bilateral; affected females—most likely unilateral lymphedema praecox
Secondary lymphedema is more common in adults and rare in children. In the United States, it is commonly from breast cancer; worldwide, due to filariasis
Affects 1.15 of 100,000 in children <20 years

RISK-FACTORS

GENETICS

Milroy disease
- Also known as hereditary lymphedema type IA
- A rare, autosomal dominant condition that affects lymphatic function
- Associated with mutations in the FLT4 gene that encodes vascular endothelial growth factor receptor 3
Meige disease
- Hereditary lymphedema type II—familial lymphedema praecox
Fabry disease
- A serious, X-linked inborn error of glycosphingolipid catabolism associated with progressive renal failure, cardiovascular disease, neuropathy, and angiokeratosis
Lymphedema-distichiasis
- An autosomal dominant condition that presents with lymphedema and double rows of eyelashes
- The condition is associated with mutations in the FOXC2 gene.
Other genetic conditions prone to lymphedema: Down, Turner, Noonan, yellow nail, Klippel-Trenaunay-Weber, and pes cavus

PATHOPHYSIOLOGY

Abnormal accumulation of interstitial fluid due to the lymphatic load overwhelming the transport capacity of lymph vessels
Lymph flow occurs under a low pressure system; unlike generalized edema, capillary filtration remains normal in patients with lymphedema.
Initially, edema is pitting, whereas chronic edema is generally nonpitting as a result of fibrosis.

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