Primary
Lymphoedema
Pathophysiology
Primary lymphoedema affects only one or two people per 100 000 under 20
years of age. Approximately 10 per cent have a positive family history.
Non
familial primary lymphoedema
It has been proposed that all cases of primary lymphoedema are due to an
inherited abnormality of the lymphatic system, sometimes termed ‘dysplasia in
utero’. However, it is more likely that many sporadic cases occur in the
presence of a (near) normal lymphatic system and are, in reality, examples of
secondary lymphoedema for which the triggering event has gone unrecognised. In
animal models, simple excision of lymph nodes and/or trunks leads to acute
lymphoedema that resolves within a few weeks, presumably due to
collateralisation.
The human condition can only be achieved by inducing extensive lymphatic
obliteration and fibrosis, for example by injecting silica particles; even then
there may be considerable delay between the injury and the onset of oedema. It
is likely that most nonfamilial primary lymphoedema is due to chronic injury
over many years due to seemingly trivial (but repeated) bacterial and/or fungal
infections, insect bites, barefoot walking (silica), deep venous thrombosis or
episodes of superficial thrombophlehitis. Primary lymphoedema is much more
common in the legs than the arms. This may be due to gravity and a bipedal
posture, the fact that the lymphatic system of the leg is less well developed
than that of the arm in terms of the volume of tissue drained, or the increased
susceptibility of the lower extremity to trauma and/or infection.
Familial
primary lymphoedema
In familial cases it is assumed that there must be some, as yet
undefined, genetic susceptibility of the lymphatic system to such injury. This
may be:
• a structural problem such as aplasia or hypoplasia
• a functional problem such as defective lymphatic contractility;
• an immune deficiency.
However, at the present time, the exact mechanisms causing familial
primary lymphoedema remain speculative.
Lymphoedema
congenita
Congenital lymphoedema
(onset at or within a year of birth) is more common in males, more likely to be
bilateral and to involve the whole leg, and accounts for less than 5 per
cent
Lymphoedema
praecox
Lymphoedema praecox (onset from 1 to 35 years of age) is three times
more common in females than males, has a peak incidence shortly after menarche,
is three times more likely to be unilateral than bilateral, usually only extends
to the
knee and accounts for about 20 per cent of primary lymphoedema. The
familial form is referred to as Meige’s disease and represents about one-third
of all cases.
Lymphoedema
tarda
Lymphoedema tarda develops, by definition, after the age of 35 years
but, in practice, is a disease of middle age. It is often associated with
obesity and, histologically, lymph nodes are replaced with fatty and fibrous
tissue. The cause is unknown. Lymphoedema developing for the first time in later
life should prompt a thorough search for underlying malignancy, particularly of
the pelvic organs, prostate and external genitalia; such malignancy may be
found in up to 10 per cent of patients. It is worth noting that in such patients
lymphoedema often commences proximally in the thigh rather than distally (Fig.
17.6).
Lymphangiographic
classification
Browse has classified primary lymphoedema on the basis of
lymphangiographic findings (Table 17.4, Fig 17.7 and
17.8). These findings are
related to the clinical presentations described above.
Megalymphatics
Some patients with lymphatic hyperplasia possess megalymphatics in
which lymph or chyle refluxes freely under the effects of gravity against the
physiological direction of flow. The megalymphatics usually end in thin-walled
vesicles on the skin surface causing excoriation, secondary infection, fluid
electrolyte and protein depletion; serous surfaces of