Familial ainhum: a case report of multiple toe involvement in a father and son, staging of ainhum with insight into different types of constricting bands.

Ainhum, also known as dactylolysis spontanea, is a painful constriction of the base of the fifth toe, frequently followed by spontaneous amputation a few years later. The disease is often symmetrical on both the feet, but, occasionally, other toes are also affected and rarely the distal phalanx of the fifth finger. 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. We hereby present a case of familial ainhum in father and son with multiple toes affected, autoamputation, and more involvement of fourth toe than the fifth toe, which is a very rare finding.

What was known?

Ainhum is an idiopathic condition affecting the fifth toe, and sometimes other toes, which is frequently bilateral with lesions in different stages.

Ainhum predominantly affects dark skinned people living in west Africa, South America, and India.

Introduction

The word ainhum means fissure in the language of the Nagos tribe of Brazil, and it may be related to ayun, the word for saw in the Lagos tribe of Nigeria.[12] The true cause of ainhum remains unclear. 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. The pathogenesis of ainhum has not been clearly elucidated. Chronic trauma, infection, hyperkeratosis, decreased vascular supply, and impaired sensation may produce excessive fibroplasia in a susceptible host. Dent et al.[3] described impaired blood supply to the foot proximal to the groove at the plantar digital junction. Poor perfusion was the result of attenuation of the posterior tibial artery and the absence of the plantar arterial arch, which led to abnormal healing after mechanical trauma.

Case Report

A 35-year-old man presented to us with pain and fissuring in his left fifth toe [Figure 1]. The patient noted a groove occurring in the inner aspect of his toe 5 years back, which gradually increased. Similar grooves started appearing in his fourth toe bilaterally since the past 2 years. At the age of 8 years, he had a similar problem affecting the right fifth toe, which gradually led to the loss of the digit as accounted by his father. On examining the father who accompanied him, it was noted that he also had similar but asymptomatic grooving involving the right fourth and fifth toes and left fifth toe [Figure 2]. The grooving was most severe in the fourth toe. The patient presented with hope to control the disease from spreading to all his digits and to prevent any further loss of his digits.

Figure 1

Left foot of son with X-ray

Figure 2

Both foot father

The patients were otherwise healthy; all his baseline investigations were done and X-ray of the foot was taken. Antibiotics were given for control of secondary infection and he was advised to prevent trauma to the foot. After control of infection, the patient was referred to plastic surgery for favor of Z plasty procedure. The patient came for regular reviews. On subsequent visits, the patient noted significant reduction in the pain following the procedure with reduction in the progression of the fissuring. The improvement was better for the son than for the father after both underwent Z plasty [Figures 3 and 4].

Figure 3

Right foot of son and father

Figure 4

Right foot father after Z plasty

Discussion

Ainhum is the progressive constriction of the base of the fifth toe, followed by spontaneous amputation. In true ainhum, dactylolysis of a 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. Cole[4] described the following four clinical stages of ainhum:

First stage: A small clavus or callus develops, which progresses to a narrow groove or fissure encircling the toe

Second stage: The toe becomes globular distal to the groove, associated with arterial narrowing and bone resorption

Third stage: Very painful; the bone separates at the joint with hypermotility of the toe

Fourth stage: Characterized by a bloodless autoamputation of the toe.

The radiographic manifestations of ainhum are diagnostic.[56] In the early stages, a radiolucent band is observed constricting the base of the toe. Osteolysis develops in the distal and middle phalanges, with a characteristic tapering effect. Ultimately, the bone narrows until it fractures and autoamputates. The radiographic appearances in pseudoainhum are similar or identical to that of true ainhum.

Differential diagnosis of ainhum includes pseudoainhum, which includes a group of conditions such as congenital amnionic bands, bands secondary to specific diseases and traumatic bands. Congenital constricting bands, also called Streeter's bands, usually involves more than one part of the body. They can involve the trunk or limbs, which affect the normal growth of that part and persist throughout life.[7] In artifactual pseudoainhum, strands of hair, fibers, or threads may be intentionally wrapped around digits or other body parts such as nipples or the penis. This phenomenon is most commonly encountered in children but can occur in mentally ill adults as well. Acquired constricting bands are associated with a variety of medical and dermatologic conditions. In general, pseudoainhum is more likely to involve any of the toes or even the hands.

Chronic dermatophyte infection, Hansen's disease, scleroderma, and severe hyperkeratosis as occurs in Vohwinkel syndrome or keratoderma hereditarium mutilans[89] may show constricting bands due to palmar and plantar hyperkeratoses.

Pseudoainhum may occur in severe psoriasis of the digits. The constricting bands of both ainhum and pseudoainhum ultimately produce a dangling, twisted digit, which can become gangrenous or infected. When this tenuous connection leads to necrosis, autoamputation occurs.

Surgery is the mainstay of therapy, and early intervention is important. In most cases of ainhum, prompt amputation helps the patient to relieve pain and prevent infection. Early cases of ainhum or pseudoainhum may respond to conservative plastic repair with a Z-plasty or similar relaxing closure that prevents further disease progression and damage to underlying structures.[10] Control of the underlying disease process may delay progression or prevent recurrence in pseudoainhum of the acquired type.

This case is presented for its unique features and to highlight the importance of early diagnosis and management in patients with ainhum, a rare but easily diagnosed dermatological condition. Ainhum as a clinical condition is underdiagnosed and overlooked because of its low prevalence and variable clinical presentations that might mimic more common etiologies, including localized trauma.

What is new?

Early diagnosis and accurate staging of ainhum are facilitated by radiological examination of the feet.

Early intervention helps in controlling the progression of ainhum and thereby saving the involved toes.

Family members should be screened for early asymptomatic involvement by ainhum.