Ainhum
Encyclopedia
Ainhum is a painful constriction of the base of the fifth toe
frequently followed by bilateral spontaneous amputation (autoamputation
) a few years later. The disease occurs predominantly in black Africans and their descendants. The exact etiology is still unclear.
, Brazil
. This disease was called “ainhum” by the Nagos and means “to saw”, characterising the painful loss of the fifth toe. The origin of these term was thought to be African. Due to slave trade, the Nagos were related to a native tribe in Nigeria
.
, South America
and India
. In Nigeria it is a common disease with an incidence of 2.2%. Daccarett recorded retrospectively a rate of 1.7% in a mainly African American population in Chicago
. Up to now only a few cases had been reported in Europe
. Ainhum usually affects people between 20 and 50 years. The average age is about thirty-eight. The youngest recorded patient was seven years old. There is no predominant gender ratio.
, fungi, bacteria
or virus
, and it is not related to injury. Walking barefoot in childhood had been linked to this disease, but ainhum also occurs in patients who have never gone barefoot. Race seems to be one of the most predisposing factors and it may have a genetic component, since it has been reported to occur within families. Dent et al. discussed a genetically caused abnormality of the blood supply to the foot. Peripheral limb angiography in five limbs with ainhum showed that the posterior tibial artery
became attenuated at the ankle, and the plantar arch and its branches were absent. The dorsal pedis artery was constituting the only supply to the forefoot and little toe.
distal to the constriction. After a time crusts can appear in the groove which can be infected with staphylococcus
.
While the groove becomes deeper, compression of tendons, vessels and nerves occurs. Bone is absorbed by pressure, without any evidence of infection. After a certain time all structures distal the stricture are reduced to an avascular cord. The toe’s connection to the foot becomes increasingly slender, and if it is not amputated, it spontaneously drops off without any bleeding. Normally it takes about five years for an autoamputation to occur. Cole describes four stages of ainhum:
• Grade I: groove
• Grade II: floor of the groove is ulcerated
• Grade III: bone involvement
• Grade IV: autoamputation has occurred
is seen in the region of the proximal interphalangeal joint with a characteristic tapering effect. Dispersal of the head of the proximal phalanx is frequently seen. Finally, after autoamputation, the base of the proximal phalanx remains. Radiological examination allows early diagnosis and staging of ainhum. Early diagnosis is crucial to prevent amputation.
, diabetic gangrene
, syringomyelia
, scleroderma
or Vohwinkel syndrome
.
could relieve pain and prevent autoamputation in Grade I and Grade II lesions. Grade III lesions are treated with disarticulating the metatarsophalangeal joint. This also relieves pain, and all patients have a useful and stable foot.
Toe
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of...
frequently followed by bilateral spontaneous amputation (autoamputation
Amputation
Amputation is the removal of a body extremity by trauma, prolonged constriction, or surgery. As a surgical measure, it is used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on individuals as a preventative surgery for...
) a few years later. The disease occurs predominantly in black Africans and their descendants. The exact etiology is still unclear.
History
Ainhum was first reported as a distinct disease and described in detail by J. F. da Silva Lima in 1867. He recognised a disease of the fifth toe suffered by the Nagos tribe of BahiaBahia
Bahia is one of the 26 states of Brazil, and is located in the northeastern part of the country on the Atlantic coast. It is the fourth most populous Brazilian state after São Paulo, Minas Gerais and Rio de Janeiro, and the fifth-largest in size...
, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
. This disease was called “ainhum” by the Nagos and means “to saw”, characterising the painful loss of the fifth toe. The origin of these term was thought to be African. Due to slave trade, the Nagos were related to a native tribe in Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...
.
Epidemiology
Ainhum predominantly affects black people, living in West AfricaWest Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
, South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
and India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
. In Nigeria it is a common disease with an incidence of 2.2%. Daccarett recorded retrospectively a rate of 1.7% in a mainly African American population in Chicago
Chicago
Chicago is the largest city in the US state of Illinois. With nearly 2.7 million residents, it is the most populous city in the Midwestern United States and the third most populous in the US, after New York City and Los Angeles...
. Up to now only a few cases had been reported in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
. Ainhum usually affects people between 20 and 50 years. The average age is about thirty-eight. The youngest recorded patient was seven years old. There is no predominant gender ratio.
Etiology and pathogenesis
The true cause of ainhum remains unclear. It is not due to infection by parasitesParasitism
Parasitism is a type of symbiotic relationship between organisms of different species where one organism, the parasite, benefits at the expense of the other, the host. Traditionally parasite referred to organisms with lifestages that needed more than one host . These are now called macroparasites...
, fungi, bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
or virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
, and it is not related to injury. Walking barefoot in childhood had been linked to this disease, but ainhum also occurs in patients who have never gone barefoot. Race seems to be one of the most predisposing factors and it may have a genetic component, since it has been reported to occur within families. Dent et al. discussed a genetically caused abnormality of the blood supply to the foot. Peripheral limb angiography in five limbs with ainhum showed that the posterior tibial artery
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
became attenuated at the ankle, and the plantar arch and its branches were absent. The dorsal pedis artery was constituting the only supply to the forefoot and little toe.
Clinical findings
The groove begins on the lower and internal side of the base of the fifth toe, usually according to the plantar-digital fold. The groove becomes gradually deeper and more circular. The rate of spread is variable, and the disease may progress to a full circle in a few months, or still be incomplete after years. In about 75 per cent both feet are affected, though not usually to the same degree. There is no case reported where it begins in any other toe than the fifth, while there is occasionally a groove on the fourth or third toe. The distal part of the toe swells and appears like a small “potato”. The swelling is due to lymphatic edemaEdema
Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...
distal to the constriction. After a time crusts can appear in the groove which can be infected with staphylococcus
Staphylococcus
Staphylococcus is a genus of Gram-positive bacteria. Under the microscope they appear round , and form in grape-like clusters....
.
While the groove becomes deeper, compression of tendons, vessels and nerves occurs. Bone is absorbed by pressure, without any evidence of infection. After a certain time all structures distal the stricture are reduced to an avascular cord. The toe’s connection to the foot becomes increasingly slender, and if it is not amputated, it spontaneously drops off without any bleeding. Normally it takes about five years for an autoamputation to occur. Cole describes four stages of ainhum:
• Grade I: groove
• Grade II: floor of the groove is ulcerated
• Grade III: bone involvement
• Grade IV: autoamputation has occurred
Symptoms
Pain is present in about 78% of cases. Slight pain is present in the earliest stage of ainhum, caused by pressure on the underlying nerves. Fracture of the phalanx or chronic sepsis is accompanied with severe pain.Histology
Histology shows a change in the prickle cell layer, and this is responsible for the laying down of condensed keratin causing the groove. The junctional tissue is reduced to a slender fibrous thread, almost avascular, and all the tissues beyond the constricting band is repressed by a fibro-fatty mass covered by hyperkeratotic integument.Imaging
Soft tissue constriction on the medial aspect of the fifth toe is the most frequently presented radiological sign in the early stages. Distal swelling of the toe is considered to be a feature of the disease. In grade III lesions osteolysisOsteolysis
Osteolysis refers to an active resorption of bone matrix by osteoclasts as part of an ongoing disease process.-Osteolysis in joint replacement:...
is seen in the region of the proximal interphalangeal joint with a characteristic tapering effect. Dispersal of the head of the proximal phalanx is frequently seen. Finally, after autoamputation, the base of the proximal phalanx remains. Radiological examination allows early diagnosis and staging of ainhum. Early diagnosis is crucial to prevent amputation.
Differential diagnosis
Ainhum is an acquired and progressive condition, and thus differs from congenital annular constrictions. Ainhum has been much confused with other diseases such as leprosyLeprosy
Leprosy or Hansen's disease is a chronic disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Named after physician Gerhard Armauer Hansen, leprosy is primarily a granulomatous disease of the peripheral nerves and mucosa of the upper respiratory tract; skin lesions...
, diabetic gangrene
Gangrene
Gangrene is a serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...
, syringomyelia
Syringomyelia
Syringomyelia is a generic term referring to a disorder in which a cyst or cavity forms within the spinal cord. This cyst, called a syrinx, can expand and elongate over time, destroying the spinal cord. The damage may result in pain, paralysis, weakness, and stiffness in the back, shoulders, and...
, scleroderma
Scleroderma
Systemic sclerosis or systemic scleroderma is a systemic autoimmune disease or systemic connective tissue disease that is a subtype of scleroderma.-Skin symptoms:...
or Vohwinkel syndrome
Vohwinkel syndrome
Vohwinkel syndome is a diffuse autosomal dominant keratoderma with onset in early infancy characterized by a honeycombed keratoderma involving the palmoplantar surfaces...
.
Treatment
Incisions across the groove turned out to be ineffective. Excision of the groove followed by z-plastyZ-plasty
Z-plasty is a plastic surgery technique that is used to improve the functional and cosmetic appearance of scars. It can elongate a contracted scar or rotate the scar tension line. The middle line of the Z-shaped incision is made along the line of greatest tension or contraction, and triangular...
could relieve pain and prevent autoamputation in Grade I and Grade II lesions. Grade III lesions are treated with disarticulating the metatarsophalangeal joint. This also relieves pain, and all patients have a useful and stable foot.