LUPUS: A GP Guide to Diagnosis
Many foot problems may occur in lupus patients and can involve skin, joints, bone, blood vessels and nerves (Table 1). The 'lupus foot' has been described as having similar abnormalities to those found in the hands, with paratendonitis, synovitis, deformity and subluxation in the toes and metatarsophalangeal joints (MPJs). 'Lupus foot' has been found in over 80% of patients with Jaccoud's arthropathy of the hands although articular symptoms in the feet have been reported less frequently than in the fingers, knees and wrists. Joint problems can lead to hallux valgus, forefoot spread and clawed or hammered toes. A high incidence of bunions and calluses has been found with these deformities along with associated pain and tenderness. Foot deformities may not be regularly reported since they are hidden and are possibly less disabling when compared to hand or finger deformities though they cannot always be attributed to lupus since they are also widespread in the general population.
It would be wrong, however, to dismiss the 'lupus foot' simply as a common structural or arthritic problem when the skin lesions that can result may be compounded by the dermatological complications of lupus. Neurological and circulatory problems such as Raynaud's phenomenon and vasculitis are common with possibly serious consequences such as digital gangrene. Steroid therapy further increases the risk of infection and peripheral ulceration so any lupus patient should warrant 'high-risk' chiropody care.
Musculo-skeletal problems include painful tenosynovitis and tendonitis possibly leading to more problems than swollen joints. Tendon rupture, particularly in weight bearing areas, has been reported - usually as complication of local or systemic corticosteroids. Plantar fasciitis is common and in some cases may even be a prodrome of lupus. Hypersensitivity of minor skin and nail lesions is frequently found. Peripheral neuropathies may occur from transverse myelitis and mononeuritis multiplex due to arteritis possibly causing major loss of foot function, although this is rare. CNS involvement is more common with the loss of muscle co-ordination, chorea, hemiplegia or sensory problems. Myalgia has been seen as a result of myositis in 50% of lupus patients and gait problems can arise from muscle atrophy and weakness around the pelvis and in the upper leg.
Two thirds of lupus patients have one or more radiographic abnormalities in their feet, mainly subluxation (37%), diffuse osteopenia (29%) or cystic changes (20%). Joint involvement is usually symmetrical often presenting in the knees, ankles, MPJs, or proximal interphalangeal joints (IPJs). There is usually tenderness and sometimes swelling, although joints often ache severely without objective signs of inflammation. Synovitis with effusions is common and deformity is often of the reducible type found with Jaccoud's athropathy although periarticular calcification and calcification of digital joint capsules has been noted. Repeated synovitis may cause a deviation and subluxation of the MPJs, with concomitant plantar pressure lesions, similar to those found in rheumatoid arthritis. Foot problems tend to be worse in patients with severe hand problems and the severity increases with time. There is an increased risk of osteoporosis from the disease process and from steroid therapy and there is a correlation between osteonecrosis and Raynaud's phenomenon. Lower limb function is at risk from avascular bone necrosis, commonly in the femoral head but also in unusual sites such as the talus, metatarsals or, occasionally, the patella.
25% of patients have nail changes, often onycholysis, or loosening of the nail. Nail growth may be slow and atrophic with pitting, leukonychia, or complete loss of the nails. Periungual erythema with telangiectasia can lead to skin atrophy around the nail and thickening of the nail plate with transverse and longitudinal ridges - often associated with acute phases of disease or with Raynaud's phenomenon. It has been suggested that the pattern of nail capillaries might demonstrate an evolution from undifferentiated to a specific collagen disease. The lupus patient often has tortuous, meandering capillaries with a prominent subpapillary plexus. Onychophosis, callus formation in the nail sulcus, is a common and painful complaint but seems especially tender in lupus. Onychophosis can lead to an ingrown toenail as the patient tries to cut down the side of the nail in an attempt to relieve the pain, causing a spike or wedge of nail to become embedded in the nail sulcus, which causes further complications such as infected hypergranulation tissue.
Corns and callus due to mechanical stress on dysfunctional feet with joint subluxations and deviations form a large proportion of the work in routine podiatry clinics, however, this hyperkeratosis may be unusual due to disease complications in the lupus patient. The pain reported is often disproportionate to clinical observations. Hyperkeratotic papules have been described as 'exquisitely tender' and lesions vary from inflamed weeping lesions to anhidrotic fissures. The pain can be severe and difficult to reduce with analgesics. Thrombocytopenia may cause haemorrhagic bullae and transient bullae may have caseous discharges. Purpura, discoid plaques and erythematous macules or papules may be present and, unusually, massive hyperkeratosis with an underlying caseous layer has been described. Atrophy of the epidermis, degeneration of the dermal-epidermal junction, dermal oedema and inflammatory infiltrate, and fibrinoid degeneration of the connective tissue have also been found.
Vascular complications seem to cause the most concern in the lower limb (Table 2), although major ischaemic problems are rare. Chilblains are common and it has been suggested that DLE patients with persistent chilblains may be at risk of developing systemic lupus. The reported incidence of Raynaud's phenomenon varies but is probably about 15-20% although Raynaud's disease has been reported to precede lupus in 30% of cases. This digital vasospasm may have an inflamed, cyanotic or ischaemic presentation and is frequently associated with chilblains but can lead to gangrene and amputation if not treated soon enough. The risk of digital necrosis is further increased by the tendency to form thromboses and embolisms due to hypercoagulation and clotting agents released due to arteritis and venulitis, in spite of thrombocytopenia. Thrombophlebitis has been found in 10% of patients and deep vein thrombosis can also be a recurrent problem. Vasculitis commonly affects small blood vessels, arterioles and post-capillary venules, forming papular, erythematous and purpuric lesions. This may also lead to splinter haemorrhages and small tender infarcts particularly around the nail fold and in the lower leg. Slowly healing ulcers may form over areas prone to pressure or trauma such as the malleoli, a problem possibly complicated by oedema from congestive heart failure, renal problems or prednisolone, or from compromise to the immune potential due to leucopenia, thrombocytopenia, haemolytic anaemia or depressed complement level. The risk of infection also rises sharply when steroid doses are greater than 40 mg per day. Macrovascular occlusive disease has been reported in a few cases leading to gangrene and lower limb amputation or arterial bypass, but this is rare.
The key aim in the treatment of the feet of any high-risk patient must be prevention of serious complications as well as reducing pain and disability. It is likely that the risk of ulceration will be increased several times if impaired circulation co-exists with foot deformities. Orthopaedic and neurological problems will lead to gait abnormalities, shoe fitting problems and increased pressure on the feet. Increased sensitivity will cause more pain, whilst decreased sensitivity may reduce the patient's awareness of potential problems. There may be localised increased ground reaction forces, a decreased ability to accommodate these with increased dermal stress resulting in the formation of corns and calluses with the risk of ulceration compounded by decreased circulation and tissue viability. Regular assessment of the feet is, therefore, important with advice to the patient about daily hygiene and inspection. There is no need to cause alarm if the lower limb is not affected by the disease but if risk factors become apparent podiatric referral becomes essential.
Treatment may involve aseptic reduction of corns and calluses with padding or strapping to decrease stress on the affected area or even splinting to stop motion in the toes or feet. Advice on footwear or possible provision of surgical shoes with insoles may be called for. Correct biomechanical control is essential and orthoses may be prescribed to reduce calcaneal eversion as a result of muscle imbalance or deformity. This may prevent or reduce compensation and wear on other joints and possible traumatic vasculitis leading to necrosis. Correct nail care is also vital and periungual problems often need skilful and sensitive treatment. Partial nail avulsion may be an option where there is co-existing nail involution or cryptosis but this may be contra-indicated by poor tissue viability leaving conservative methods of nail and hypertrophied skin reduction with nail-sulcus packing as the options of choice combined with footwear and home-care advice.
The treatment of podiatric problems obviously needs to be wide ranging and will frequently call for a multi-disciplinary approach with professionals such as wound care nurses, physiotherapists and orthotists, monitored by the specialist in connective tissue disease. The risk of serious podiatric complications would suggest that all patients with lupus could benefit from referral to a chiropodist or podiatrist.
The hospital team approach may be available for those with obvious or severe problems, whose disabilities may well also entitle them to NHS chiropody care in the community, but those with relatively minor or early risk signs may not receive professional examination. More serious problems could be avoided in this group by early examination, preventative treatment and advice. This has already been found to be cost effective and to reduce morbidity and amputation with other disease processes such as diabetes.
NHS chiropody care (which may depend on the individual purchasing authority) is available to the elderly, school children, pregnant women and 'the handicapped'. This could exclude young adult lupus patients with no disability, however, it is common practice to see those 'at risk' as a result of impaired circulation. It is under this 'at risk' category that all patients with lupus should be seen at least for an annual check-up (Table 3).
Table 1 - Foot problems in SLE |
Table 2 - Possible Lower Limb Vascular Problems |
Table 3 - Risk Factors Affecting the Lupus Foot |
Stephen Miller SRCh, BSc, MA.
Locality Chief Chiropodist
Paytons House
Ridge Hill
Wordsley
West Midlands, DY8 5ST