Black Heel (Calcaneal Petechiae)

Background

Black heel (calcaneal petechiae) is a self-limited, asymptomatic, trauma-induced darkening of the posterior or posterolateral aspect of the heel. It occurs primarily in young adults who are engaged in athletic activities, including tennis, football, and gymnastics.^[1] Black heel was first described in a group of basketball players in 1961.^[2]

Although clinically insignificant, black heel is important because of its close clinical resemblance to melanoma.

A similar lesion termed black palm (tache noir) has been described on the thenar eminence in weightlifters, gymnasts, golfers, tennis players, mountain climbers, and baseball players.^[3] Superficial cutaneous hemorrhages of other areas of the feet have been published in the literature.^{[4, 5, 6, 7]}

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Pathophysiology

Black heel (calcaneal petechiae) is caused by a repeated lateral shearing force of the epidermis sliding over the rete pegs of the papillary dermis. This damages the delicate papillary dermal capillaries, resulting in intraepidermal hemorrhage.

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Epidemiology

Frequency

The exact incidence of black heel (calcaneal petechiae) is unknown. One study involving 596 19-year-old sports participants revealed an incidence of 2.9%.^[8] This sports-related dermatosis probably is much more common than has been reported.

Age

Black heel (calcaneal petechiae) primarily occurs in young adult athletes, but it may appear in persons of any age if the appropriate conditions occur.

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Prognosis

Prognosis for black heel (calcaneal petechiae) is excellent. Complete clearing is achieved with cessation of the causative activity usually within 2-3 weeks of rest. The lesion of black heel (calcaneal petechiae) usually is asymptomatic, although both pain and tenderness can occur. The black areas always resolve spontaneously if the traumatic inciting events are discontinued.

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History

Black heel (calcaneal petechiae) occurs in adolescents and young adults who participate in sports that involve frequent starts and stops, such as basketball, football, soccer, lacrosse, and racquet sports. Additionally, constant pounding on hard surfaces causes injury of the heel against the back of the shoe in runners.^[9]

Patients present with an irregular dark macule over the heel, as shown in the image below.

View Image

Linear petechiae on the heel, characteristic of black heel.

The lesion usually is asymptomatic and does not inhibit the patient from performing routine daily activities. The patient may or may not relate the onset of the lesions to participation in sports.

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Physical Examination

Examination reveals a blue-to-black macule or patch ranging in size from a few millimeters to several centimeters in diameter. The posterior and posterolateral heel are affected most commonly. On close inspection, multiple petechiae are centrally aggregated with a few scattered satellite macules. The dyschromia often is in a horizontal distribution; however, both circular and oval lesions may occur.

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Laboratory Studies

The most important goal is to differentiate black heel (calcaneal petechiae) from melanoma. No specific workup is necessary to make the diagnosis of black heel.

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Imaging Studies

Epiluminescence techniques, such as dermatoscopy and video macroscopy, can be used to aid in the differentiation of melanoma from black heel.^{[10, 11]} Under the dermatoscope, black-reddish globules on the ridges (resembling pebbles) are characteristic.^[12] If doubt persists, rapidly process the shaved fragments of keratin with commonly available screening tests used for detection of occult blood.

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Procedures

The diagnosis of black heel (calcaneal petechiae) is clinical and can be aided by paring down the lesion with a surgical blade. Melanocytic lesions do not lose their pigmentation with paring, while black heel may clear completely after the stratum corneum is removed.

A biopsy is indicated if the diagnosis remains in doubt, but this is seldom necessary.

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Histologic Findings

Hyperkeratotic stratum corneum typical of acral skin is seen; parakeratosis is common. Extravasated erythrocytes in the dermal papillae are characteristic. Often, biopsy is only performed to the stratum corneum and the hemorrhage can be identified as loculated serum and degenerated erythrocytes.^[13]

Phagocytosis of extravascular RBCs and subsequent degradation of hemoglobin to hemosiderin does not occur; therefore, traditional iron stains do not work and histochemical stains must be directed toward hemoglobin. Benzidine stain reveals brown homogenous clusters of hemoglobin.^{[14, 15]}

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Medical Care

Treatment is not necessary for black heel (calcaneal petechiae) because the lesion resolves spontaneously with discontinuation of the causative activity. The placement of a felt pad in the heel of the shoe may be curative.

Skin lubrication, heel cups, a change of footwear, wearing two pairs of thick socks, and a break from training may reduce the incidence of black heel (calcaneal petechiae).^[9]

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Surgical Care

Paring down the black heel (calcaneal petechiae) lesion with a scalpel blade may result in a complete clearing of the dyschromia.

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Activity

Sports participation can be continued without harm to the patient, although the black heel (calcaneal petechiae) persists unless padding is added to the heel of the athletic shoe.

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