Introduction
Background
Ainhum is the autoamputation of a digit, usually of the fifth toe bilaterally and as a result of a constricting scar in the form of a band or groove. Pseudoainhum is a similar condition that occurs as a secondary event resulting from certain hereditary and nonhereditary diseases that lead to annular constriction of digits.
Ainhum predominantly affects black patients in tropical regions. Although it has been reported in temperate areas, ainhum appears to be increasingly less common in the United States.1,2
The origin of the term ainhum is unclear. In 1867, the term was used by da Silva Lima3 from Bahia, Brazil to report the first published case. The word ainhum means fissure in the language of the Nagos tribe of Brazil and may be related to ayun, the word for saw in the Lagos tribe of Nigeria. The synonym for ainhum is dactylolysis spontanea.
Pathophysiology
In true ainhum, dactylolysis of a toe (most commonly, but not always,4 the fifth toe) most likely is triggered by trauma; however, the true cause remains unknown. The trauma may be related to walking barefoot in the tropics. A fibrotic band develops from a flexural groove and progressively constricts the full radius of the toe until spontaneous autoamputation occurs. A similar progression occurs in pseudoainhum because of a collagen band, rather than from fibrosis. Pseudoainhum may be acquired or congenital. Additionally, ainhum occasionally affects fingers.
Ainhum of the finger. Courtesy of Hon Pak, MD, and reviewed by Ross Levy, MD.
Frequency
United States
Approximately 130 cases have been reported in the United States, but only 30 cases have been reported since 1960. Pseudoainhum is a rare disorder.
International
Ainhum is a relatively common disease among black Africans. In Africa, the incidence range is 0.2-2%. The incidence of true ainhum outside of Africa appears to be low.
Mortality/Morbidity
Pain may be severe in ainhum and in pseudoainhum. Because ainhum occurs primarily in tropical areas, secondary infections and their complications may be a source of morbidity.
Race
Ainhum has been reported to affect all races but occurs predominately in blacks. No racial predilection exists for pseudoainhum.
Sex
In Nigeria, one study revealed an incidence of 2.48 cases per 1000 males and 1.08 cases per 1000 females; however, recent investigations suggest no sex preference.
Age
Full-blown ainhum is uncommon in persons younger than 30 years and older than 50 years. The reason ainhum appears to be age specific is unclear. Early lesions may be observed in childhood.
Clinical
History
Cole5 has described 4 clinical stages of ainhum.
- In the first stage, a small clavus or callus develops on the medial aspect of the plantar fold of a toe (usually the fifth) that progresses to a narrow groove or fissure. This groove deepens and slowly encircles the toe. Progression may be slow and can develop first in childhood. The deepening of the fissure is associated with pain in 78% of patients but is less intense than pain in the third stage.
- The second stage is shorter because the toe becomes globular distal to the groove, which is associated with arterial narrowing and bone resorption.
- In the third stage, the bone separates at the joint with hypermotility of the toe. Pain may be intense.
- The fourth stage is characterized by a bloodless autoamputation of the toe at the site of the encircling band.
Physical
The clinical presentation depends on the stage to which the ainhum has progressed.
- The initial sign of a painful fissure under a toe may not be defining, but the progressive constriction at the base of the toe with distal edema is diagnostic of ainhum.
- The toe may become rotated, clawed, and dorsiflexed at the metatarsophalangeal joint.
- Ultimately, before the toe is shed, it may be attached by an increasingly slender thread of fibrous tissue.
- The clinical, histologic, and radiographic appearances in pseudoainhum are similar or identical to true ainhum.
Causes
In 1952, Wells and Robinson6 proposed 4 distinct sources of annular constrictions of the digits. The sources include (1) annular scarring from frostbite, burns, or trauma, (2) true ainhum, (3) constricting bands that simulate ainhum, and (4) congenital bands.
The exact etiology of true ainhum is unclear. Race and climate apparently are predisposing factors. Ainhum also may have a genetic component, since ainhum has been reported to occur within families. Infection and walking barefoot in childhood are linked to ainhum but probably are not major factors in its development. Abnormal scarring does not appear to be a cause; ainhum and keloid formation rarely occur in the same individual.
Pseudoainhum may be acquired or congenital.
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References
Greene JT, Fincher RM. Case report: ainhum (spontaneous dactylolysis) in a 65-year-old American black man. Am J Med Sci. Feb 1992;303(2):118-20. [Medline].
Mendelson DS, Chan KF, Song IS. Spontaneous dactylolysis with pain in a 58-year-old American Black man. JAMA. Oct 2 1981;246(14):1591-2. [Medline].
da Silva Lima JF. On ainhum. Arch Dermatol. 1880;6:367.
Olivieri I, Piccirillo A, Scarano E, Ricciuti F, Padula A, Molfese V. Dactylolysis spontanea or ainhum involving the big toe. J Rheumatol. Dec 2005;32(12):2437-9. [Medline].
Cole GJ. Ainhum: An account of fifty-four patients with special reference to etiology and treatment. J Bone Joint Surg Br. Feb 1965;47:43-51. [Medline].
Wells TL, Robinson RC. Annular constrictions of the digits. AMA Arch Derm Syphilol. Nov 1952;66(5):569-72. [Medline].
Cunliffe WJ. Ainhum and pseudo-ainhum. In: Rook A, Wilkinson DS, Ebling FJ. Textbook of Dermatology. Vol 2. Oxford: Blackwell Scientific; 1979:1638.
Demis DJ. Ainhum, pseudoainhum, and tourniquet syndrome. In: Demis DJ, Dobson RL, McGuire J. Clinical Dermatology. 7th ed. Hagerstown, Md: Harper & Row; 1979:4-47.
Fetterman LE, Hardy R, Lehrer H. The clinico-roentgenologic features of ainhum. Am J Roentgenol Radium Ther Nucl Med. Jul 1967;100(3):512-22. [Medline].
Jemmott T, Foster AV, Edmonds ME. An unusual cause of ulceration: ainhum (dactylolysis spontanea). Int Wound J. Sep 2007;4(3):251-4. [Medline].
Rossiter JW, Anderson PC. Ainhum: treatment with intralesional steroids. Int J Dermatol. Jun 1976;15(5):379-82. [Medline].
Allyn B, Leider M. Dactylolysis spontanea (ainhum). Report of a case treated by the surgical procedure known as Z-plasty. JAMA. May 25 1963;184:655-7. [Medline].
Browne SG. Ainhum. Int J Dermatol. Jun 1976;15(5):348-50. [Medline].
Dent DM, Fataar S, Rose AG. Ainhum and angiodysplasia. Lancet. Aug 22 1981;2(8243):396-7. [Medline].
Hunt M, Glucksman EE. Ainhum presenting to the accident and emergency department. Arch Emerg Med. Dec 1993;10(4):324-7. [Medline].
Kean BH, Tucker HA, Miller WC. Ainhum: a clinical summary of forty-five cases on the Isthmus of Panama. Trans R Soc Trop Med Hyg. 1946;39:331-4.
Ramesh V, Misra RS, Mahaur BS. Pseudoainhum in porokeratosis of Mibelli. Cutis. Feb 1992;49(2):129-30. [Medline].
Schulz EJ. Genodermatoses. Dermatol Clin. Oct 1994;12(4):787-96. [Medline].
Sharma RC, Sharma AK, Sharma NL. Pseudo-ainhum in discoid lupus erythematosus. J Dermatol. Apr 1998;25(4):275-6. [Medline].
Further Reading
Keywords
ainhum, dactylolysis spontanea, bankokerend, sukhapakla, autoamputation of a digit, pseudoainhum, pseudo-ainhum, annular constriction of a digit
