What is podoconiosis?
Podoconiosis, also known as nonfilarial elephantiasis, is a form of lymphoedema affecting the lower limbs that occurs in people with long-term exposure to volcanic red clay soil.
Who gets podoconiosis?
Podoconiosis is endemic in tropical regions of Africa, Asia and Central America.
- Podoconiosis is present in communities living at high altitude (above 1000 m) where there are volcanic red clay soils.
- Long-term exposure occurs in rural communities where genetically susceptible individuals are most likely to be exposed in the home and through their occupation.
- Symptom onset begins ten to twenty years of constant exposure with a progressive increase in prevalence up to sixty years .
What causes podoconiosis?
Podoconiosis is a genetically determined abnormal inflammatory reaction to mineral particles in red clay soils derived from volcanic deposits. The suggested pathogenesis is:
- Absorption of soil particles through fissures in the sole of the foot
- Lymphocytic reaction to the particles
- Subsequent oedema (fluid build-up) and fibrosis
- Dilation and stiffening of the vessels causes valvular dysfunction
- Attachment of dermis and subdermis to deep fascia
- Narrowing and obliteration of the lymphatic vessels
- Destruction of hair follicles, sweat and sebaceous glands .
There is no contagious or infectious organism identified.
What are the clinical features of podoconiosis?
Cutaneous symptoms and signs associated with podoconiosis include:
- Lichenification, associated with stiffness in first web space — Stemmer sign
- Dermal nodules are elevated, non-translucent lesions 0.5 cm in width and length.
- Dermal ridges are elevated lesions 0.5 cm in width. These ridges are longer in length than in width.
- Dermal bands are palpable ridges that are not elevated.
- Longitudinal skin markings are most striking between first and second toes, exaggerated by scrunching toes.
- Serous ooze
- Mossy changes: rough velvety skin surface with round or fusiform fluid-filled or papillomatous, hyperkeratotic horny lesions in slipper pattern around heel and border of foot. [1, 2, 3]
- Pruritus and/or burning sensation over foot and lower limb
- Swelling of the foot and lower limb
- Increased diameter of the leg
- Block toes and splaying of forefoot, which cause the big toes to knock together
Podoconiosis is a chronic condition commonly complicated by acute episodes of lymphadenitis, especially when fibrotic. Acute lymphadenitis presents as:
- Pain in the limb
- Warmth of the limb
- Tender femoral lymph nodes
- Further increase in the size of the limb.
Podoconiosis presents with ascending lymphoedema.
- Lymphoedema is commonly bilateral, but can sometimes be asymmetrical.
- Lymphoedema begins in the foot progressing proximally up the lower limb. It usually stops before the groin.
- Swelling can take two forms: a soft and fluid, ‘water-bag’ type; or hard and fibrotic, ‘leathery’ type, often associated with multiple hard skin nodules.
Podoconiosis has an early prodromal phase prior to the development of elephantiasis.
Acute attacks resolve spontaneously after a few days of rest and elevation. Subsequent episodes typically affect the same limb. Patients have an acute attack on average five times a year [1, 2].
The following staging system was designed for use by field workers. Each leg should be staged separately for:
- presence (M+) or absence (M) of mossy changes
- the greatest below-knee circumference.
Stage one: swelling reversible overnight.
The swelling is not present when the patient first gets up in the morning.
Stage two: below-knee swelling that is not completely reversible overnight. If present, knobs/bumps are below-knee ONLY.
- Dermal knobs or bumps appear in form of nodules, ridges or bands.
- Tourniquet-like effects are observable at this stage, depending on the position of dermal ridges and nodules in relation to joints.
- Mossy changes may be apparent, but their presence depends on a range of factors, such as the use of plastic footwear.
- Nail dystrophy may develop.
- Interdigital maceration and hyperpigmentation are often present at this stage.
Stage three: below-knee swelling that is not completely reversible overnight; knobs/lumps present above the ankle
- Persistent swelling that does not reach above the knee.
- Dermal nodules, ridges or bands appear above the ankle.
- Tourniquet-like effects are frequently observed at this stage.
- Features mentioned in stage 2 may also be present.
Stage four: Above-knee swelling that is not completely reversible overnight; knobs/bumps present at any location.
- Persistent swelling that is present above the knee.
- Signs of lymphectasia may be apparent, particularly on the thigh.
- Features mentioned in stage 2 may also be present.
Stage five: Joint fixation; swelling at any place in the foot or leg
- The ankle or interphalangeal joints become fixed and difficult to flex and dorsiflex.
- This may be accompanied by adhesion and fusion of the toe web spaces, making the toes appear short or indistinct.
- Sensation is preserved.
- X-rays show tuft resorption and loss of bone density .
What are the complications of podoconiosis?
Complications of podoconiosis include:
- Secondary bacterial infection
- Loss of work
- Social isolation
How is podoconiosis diagnosed?
Podoconiosis is diagnosed clinically. Diagnosis is based on clinical features, patient history and exclusion of other causes of lymphadenitis.
What is the differential diagnosis for podoconiosis?
Podoconiosis differential diagnosis includes other causes for elephantiasis:
- Lymphatic filariasis. This is found at lower altitudes. Swelling is often first noticed in the groin and then descends. It is usually unilateral and stops above the knee.
- Lymphoedema due to leprosy — sensation is lost from the heel but preserved in the toes and forefoot. Trophic ulcers, thickened nerves or hand involvement may be observed.
- Endemic Kaposi sarcoma
- Chronic recurrent erysipelas
- Elephantiasis nostras verrucosa (chronic lymphoedema)
What is the treatment for podoconiosis?
Podoconiosis treatment aims to reduce lymphoedema and to prevent relapse by reducing re-exposure to the causative soil.
Primary prevention requires avoiding prolonged contact between skin and soil.
- Covered footwear
- Floor covering in homes
Treatment after podoconiosis has occurred involves:
- Foot hygiene
- Covered footwear
- Compression bandaging
- Relocation of living and working environments
- Emollient to improve skin barrier function.
More severe disease may require:
- Elevation at least 18 hours per day
- Compression bandaging [1, 2].
Surgical management has been attempted. Shave excision of hard nodules has been used with secondary intention healing. Surgical removal of tissue followed by skin grafting (Charles operation) is unsuccessful, as scar tissue aggravates symptoms .
What is the outcome for podoconiosis?
Podoconiosis results in progressive swelling and disfigurement of the limbs. Untreated patients are typically in constant pain and discomfort and may suffer from chronic infections. Due to social stigmatism, individuals with podoconiosis are often ostracised from their communities [1, 2].