A 42-year-old woman was admitted to the hospital for complications related to type 2 diabetes. Her inpatient team noticed that her right fifth finger was swollen, red, and appeared to have a fissure. The patient stated that although the fissure was not present since birth, her finger has looked this way for “a while” and typically did not bother her. On examination, she had hyperkeratotic plaques on some of her fingers. She denied trauma to the site of injury and her family and travel history were unremarkable.
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The patient’s presentation is consistent with the formation of a constricting band around her right fifth digit. This rare and poorly understood process may progress to autoamputation. It was first described in the medical literature in the early 1800s.1
The terminology surrounding this process is somewhat confusing — constricting band, ainhum, pseudoainhum, dactylolysis spontanea — and has led to misclassification in the literature. In today’s vernacular, ainhum refers to an idiopathic, constricting band or groove that forms on the digits of dark-skinned patients in tropical or subtropical countries that can progress to spontaneous dactylolysis and spontaneous amputation.2 West African and Brazilian tribal languages have terms similar to ainhum that mean “to saw or file” and “fissure,” respectively.2
Pseudoainhum describes an analogous process that develops as a result of an associated disease process (not idiopathic).2 It has been further subclassified by some as either a primary process presenting at birth or early in life or a secondary process presenting later in life. Pseudoainhum is not associated with any particular ethnic background, and it can occur anywhere on the body.
Ainhum has been reported to have an incidence of 0.015% to 2.2% in tropical and subtropical climates but is exceedingly rare in North America.3,4 Likewise, pseudoainhum is extremely rare, and no data on the incidence have been published. The etiology of these conditions is poorly understood. Whereas ainhum is an idiopathic process, the etiology of pseudoainhum is attributed to the condition(s) with which it is associated, including mechanical effects associated with hyperkeratosis (which often is present), infection, and vascular changes.2
Pseudoainhum has been reported in association with several conditions, including disorders of keratinization (Vohwinkel syndrome), psoriasis, diabetes, Raynaud phenomenon and scleroderma, syphilis, leprosy, and trauma (such as a hair wrapped around the digit).2
Typically, this condition is identified easily with recognition of the fissure. It tends to progress through stages, beginning with the formation of a circumferential groove or crease, followed by edema and deepening of the fissure, with corresponding arterial narrowing. This is followed by separation of the bones from the joint and eventually autoamputation, leaving a dangling and twisted digit. In the final stage, necrosis completes the amputation. There often is associated hyperkeratosis, and pain may or may not be present. Ainhum tends to present on the fifth digit of the toe, whereas pseudoainhum can present on any digit or even on the extremities.3,4
The diagnosis typically is made by history and clinical examination. A biopsy at the site of constriction will show hyperkeratosis and fibrosis. In pseudoainhum, a biopsy may provide a clue to the associated condition if related changes are recognized (such as psoriasis or a foreign body); thus, it may be diagnostically useful in that situation. A lucent band may be seen on radiograph, along with osteolysis in advanced cases.
The clinician should distinguish this condition from others that may appear clinically similar: frostbite, distal gangrene in patients with diabetes, or congenital maldevelopment of the digits or extremities. In these cases, however, a fissure corresponding to a constricting band would not be present. Infants may present with hair or thread wrapped around a digit, leading to a very similar clinical scenario termed hair-thread tourniquet syndrome.5
In the case of pseudoainhum, the provider should perform a workup that includes family history and possibly genetic testing for associated conditions, including diabetes, connective tissue diseases, psoriasis, and certain genodermatoses. The patient also should be evaluated for a history of trauma or foreign body at the site.
Treatment efficacy is limited. If an associated or underlying condition can be determined, targeted therapy may be helpful. In hyperkeratotic conditions, a topical keratolytic or oral agents such as etretinate or isotretinoin may provide some benefit, but there may be relapse upon discontinuation of the treatment.6,7
Surgery aimed at releasing the constricting band via a z-plasty or excision with skin grafting can be attempted.8 Surgery typically is indicated when the constricting band is symptomatic or causing neurovascular compromise. Amputation may be the only viable solution in advanced cases of impending autoamputation.
The patient in this case was evaluated by a hand surgeon and not deemed to be in need of urgent surgery because she had good perfusion and mobility of the digit. She was started conservatively on a topical keratolytic agent, with a plan to visit the outpatient clinic. She subsequently was lost to follow-up.
Andrew Fischer, MD, is a board-certified dermatologist at Elite Dermatology in Houston, Texas.
- Peterka ES, Karon IM. Congenital pseudoainhum of the fingers. Report of a case. Arch Dermatol. 1964;90:12-14.
- Rashid R, Cowan E, Abbasi SA, Brieva J, Alam M. Destructive deformation of the digits with auto-amputation: a review of pseudo-ainhum. J Eur Acad Dermatol Venereol. 2007;21(6):732-737.
- Cole GJ. Ainhum: an account of 45 patients with special reference to etiology and treatment. J Bone Joint Surg Br. 1965;47:43-51.
- Kean BH, Tucker HA, Miller WC. Ainhum; a clinical summary of 45 cases on the Isthmus of Panama. Trans R Soc Trop Med Hyg. 1945-1946;39(4):331-334.
- Mat Saad AZ, Purcell EM, McCann JJ. Hair-thread tourniquet syndrome in an infant with bony erosion: a case report, literature review, and meta-analysis. Ann Plast Surg. 2006;57(4):447-452.
- Chang Sing Pang A, Oranje A, Vuzevki VD, Stolz E. Successful treatment of keratoderma hereditaria mutilans with an aromatic retinoid. Arch Dermatol. 1981;117(4): 225-228.
- Camisa C, Rossana C. Variant of keratoderma hereditaria mutilans (Vohwinkel’s syndrome). Treatment with orally administered isotretinoin. Arch Dermatol. 1984;120(10):1323-1328.
- Simkin D, Ho JD, Simkin DJ, Tomany K. A novel association of pseudoainhum and epidermolytic ichthyosis, successfully treated with full thickness skin graft after failed z-plasty repair. Dermatol Online J. 2018;24(1):13030/qt1ph217qf.