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Primary lymphoedema
Aetiology
Although by definition the cause of primary lymphoedema is obscure, some factors clearly influence its development. The small number of babies who have lymphoedematous limbs at birth usually have ‘aplastic’ and truly absent lymphatics. This condition (Milroy's disease) has a clear genetic predisposition in some families. How, and why the lymphatic system is damaged or malformed, is not known, but other congenital abnormalities such as yellow nails, distercerciasis, and Pierre-Robin syndrome may coexist. Some degree of inheritance can be demonstrated in about one-third of all patients with primary lymphoedema. Congenital abnormality or absence of the lymphatics does not explain why lymphoedema develops relatively late in most patients, the most common age of onset being between 10 and 25 years of age.
It is possible that the constituents of the lymph draining through the lymphatics may damage the lymphangioles or lymph nodes. Lymph may contain large amounts of fibrinogen under certain circumstances, and this may coagulate and block the lymphatics; abnormal lymph may also cause nodal fibrosis which may lead to ‘die-back’, or disappearance of the lymphangioles. The primary disease may therefore be in the node, and this may cause the lymphatic hypoplasia. Anticoagulant therapy has been reported to produce improvement in patients with lymphoedema, lending some support to the concept that hypercoagulability of lymph may be harmful. Molecules as yet unrecognized within lymph may also be harmful to nodes and lymphatic vessels. None of these explanations accounts for the development of hyperplastic or dilated lymphatics.
Clinical features
Primary lymphoedema is much more common in the lower limbs than in the upper limbs: although this is partly explained by the influence of gravity, anatomical abnormalities are rarely present in the lymphatics of the upper limb.
The swelling may affect one or both lower limbs, the lower abdomen, the genital region, one or both upper limbs, and, rarely, the face or chest. In the lower limbs swelling usually develops around the ankle and on the dorsum of the foot, and spreads proximally (Fig. 11) 652. In the majority of patients the oedema does not spread above the knee, but severe oedema of the whole limb including the buttock  suggests a proximal nodal lymphatic occlusion. There are exceptions to this rule, however, and patients with proximal lymphatic occlusions may have no oedema of the ankle or foot. Because lymphatic oedema is chronic and has often been present for many years it stimulates a fibrotic reaction in the subcutaneous tissues, making them more resistant to deformation than is the case in acute oedema associated with cardiac failure or hypoproteinaemia. However, prolonged digital pressure will always produce a ‘pit’. If such pitting cannot be demonstrated the diagnosis of lymphoedema must be questioned and another cause for the swelling should be sought.
The onset of the swelling is usually insidious, and it may fluctuate. Even when lymphoedema becomes fixed all patients report that the swelling decreases during sleep and is maximal at the end of the day. Onset can occasionally be sudden, and progression rapid. This is often associated with cellulitis, which can be both a cause and a result of lymphoedema. Patients with sudden severe swelling usually have a proximal lymphatic occlusion and may have an underlying cause for the condition. Patients with malignant obstruction of both the veins and lymphatics often develop a severe brawny oedema of rapid onset that can cause intractable pain which may be very difficult to alleviate. Some patients develop marked cutaneous thickening which can progress to lymphatic warts (condylomata) and multiple coarse papillae. Other patients are troubled by repeated attacks of cellulitis. The infecting agent may enter through the hyperkeratotic skin or through cracks in the interdigital clefts which occur in athletes' foot.
Occasionally patients develop numerous vesicles in the skin which may leak clear lymph or, occasionally, chyle. These vesicles usually indicate that there are megalymphatics  and lymphatic reflux. Vesicles usually arise over the upper thighs or on the external genitalia, and they may also act as a portal of entry for bacteria. Occasionally the lymph leakage from these vesicles is severe enough to be a major source of embarrassment and irritation.
Severe oedema of the male genitals is both embarrassing and uncomfortable, interfering with work and sexual relationships. Penetration may be impossible and urination may be difficult when the penis is almost hidden inside a grossly swollen scrotum. Leaking vesicles and recurrent attacks of cellulitis often complicate the condition. Women with genital oedema usually have fewer problems but massive labial swelling can be uncomfortable and embarrassing.
Lymph can leak into both the abdominal and pleural cavities, causing chylous ascites and pleural effusions. Patients present with abdominal distension, dyspnoea, or both. These problems are usually the result of leakage from refluxing megalymphatics; chyluria and chylous leakage from the vagina are rare complications. Protein-losing enteropathy can cause severe weight loss and chylous leakage from the serosal surface of the bowel may increase the ascites.
Lymphoedema may occasionally affect the upper limb, including the fingers (Fig. 16) 657 and unilateral pectoral swelling can also occur. Oedema of the face usually presents as swelling of the eyelids, which are the most lax tissues in this region.
Patients with lymphoedema usually seek advice because they want to know the cause of the swelling, which causes major cosmetic embarrassment, even though it is often only of nuisance value. Severe swelling may make it impossible to buy shoes, and if the limb continues to swell its weight interferes with normal walking. Recurrent attacks of cellulitis may also be a major problem. Lymphangiosarcoma (Stuart Treves syndrome can infrequently develop in limbs following long-standing lymphoedema, but is more often a problem in patients with secondary lymphoedema.
A detailed past and family history should exclude secondary causes of lymphoedema and should suggest a possible inheritance of the primary condition. Apart from confirming the presence of pitting, physical examination excludes other causes of limb swelling and reveal any associated abnormalities. ‘Square toes’ often result when footwear prevents toe expansion. It is important to inspect the web spaces between the toes for athletes' foot, which is especially common in lymphoedematous limbs and is an important portal of entry for bacteria that cause recurrent cellulitis. Yellow nail syndrome is occasionally associated with lymphoedema, as is distichiasis (two layers of eyelashes). Occasionally Pierre-Robin syndrome (micrognathia) and other skeletal abnormalities are present, and congenital cardiac anomalies are found also in patients with lymphatic hyperplasia.
The skin should be carefully examined for papillae and vesicles, and the limbs should be measured at fixed levels, above and below fixed bony points, to allow both the natural history and the results of therapy to be evaluated. The length of the limbs should also be measured and the presence of any abnormal veins must be recorded. The abdomen and chest should be carefully examined for ascites or effusions. The groins and axillae should be palpated for pathologically enlarged lymph nodes. Rectal and vaginal examinations are indicated if a pelvic malignancy is suspected.
The physical examination should provide indications of whether the patient has primary or secondary lymphoedema, but unequivocal confirmation of the diagnosis is desirable. If the swelling is not the result of lymphoedema, other investigations are necessary.
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