Environmental and Sports-Related Skin Diseases

Introduction

Humans, like all other mammals and all birds, are homeothermic organisms that maintain their core body temperature within a narrow range by varying cutaneous and visceral blood flow. Normal core body temperatures vary between 36°C and 37.5°C (96.8°F and 99.5°F). At normal core temperature, cutaneous blood flow is about 4% of cardiac output or 250 ml/min. Modulation of cutaneous blood flow is performed by the hypothalamus via a delicate balancing act between heat retention and loss. Cutaneous, muscle, and spinal cord temperature sensors send signals to the preoptic area of the anterior hypothalamus. Communication with the posterior hypothalamus sets up the subconscious thermoregulatory mechanisms of vasomotor control, sweating, and shivering.

When prolonged exposure to a hot environment leads to an increase in core temperature, the subsequent decrease in sympathetic output results in peripheral vasodilation, allowing an increase in cutaneous blood flow of up to 6–8 L/min. Cholinergic output stimulates sweating. These changes allow radiant, conductive, convective, and evaporative heat loss. In contrast, cold temperature exposure leads to increased sympathetic output with peripheral vasoconstriction. Countercurrent heat exchange between parallel arteries and veins further reduces heat loss to the skin, thereby conserving core heat. The behavioral response of shivering generates heat through muscular activity .

Pathologic conditions arise when the normal hypothalamic regulatory set point is overcome by extremes of temperature ( Table 88.1 ). The following discussion will explore heat-related illnesses and thermal burns. Heat-induced urticaria is covered in Chapter 18 .

History

It has been speculated that King Edward and his armored crusaders lost the final battle of the Holy Land because the Arab horsemen were adapted and dressed appropriately for the severe heat.

Epidemiology

The frequency of heat-related illnesses is unknown, since milder forms resolve with simple measures. Heat-related illness accounted for more than 8000 deaths in the US between 1979 and 1999, and is responsible for ~7% of wilderness deaths . The European heat wave of 2003 contributed to the deaths of about 14 800 individuals in France. The highest recorded incidence of heat-related deaths during sports participation occurred in the US between 2005 and 2009 . Risk factors are listed in Table 88.2 .

Burn injuries are far more commonly reported, occurring in 2 million people per year in the US alone, and resulting in 60 000 hospitalizations and 6000 deaths, half of which occur in children . The male to female ratio is 2 : 1. The main sources of burns in children are scald, flame, and electrical. Abuse or neglect may account for up to 20% of pediatric burns. Mortality rates have declined in recent years due to improved resuscitative and surgical management. In the 1940s, burns in children involving 50% body surface area (BSA) had a 50% survival rate, whereas today, 50% of children with 90% BSA burns survive .

A unique form of burn injury is that due to fireworks. In the US alone, there were at least 25 000 emergency department visits for injuries due to fireworks between 2006 and 2010. Half of the visits were by individuals <20 years of age, with a predominance of male patients (~75%). The most common injuries were distal extremity burns, followed by ocular injury, open wounds of distal extremities, and ocular burns .

Pathogenesis

Athletic activity can generate 800 to 1000 kcal/h of heat for prolonged periods. This results in a 1°C rise in core body temperature every 5 to 8 minutes. The normal thermoregulatory mechanisms dissipate this heat as it is generated. When these regulatory mechanisms fail, heat injury occurs. Heat illnesses are not defined by a specific temperature, but by the abnormal response to heat. Table 88.1 outlines the pathogenesis of heat-related disorders.

Thermal burns occur when skin is exposed to infrared radiation (800 to 170 000 nm) from an external heat source with a temperature exceeding 44°C (111°F). Time and temperature curves have been developed to determine maximum threshold thermal exposure times. Necrosis of the epidermis occurs in about 45 minutes at 47°C (117°F) but in only 1 second at 70°C (158°F). Denaturation and coagulation of cellular proteins occur in thermal injury. Interstitial edema develops from altered osmotic pressure and capillary permeability. Several chemical mediators with vasoactive and tissue-destructive properties are released, including prostaglandins, bradykinin, serotonin, histamine, lipid peroxides, and oxygen radicals .

Clinical features

Although heat-related illnesses are not primary skin diseases, they can present with cutaneous findings. Their clinical features are summarized in Table 88.1 .

Thermal burns of the skin differ in their clinical presentation, depending upon the depth of injury ( Table 88.3 ) . Conventional nomenclature categorizes cutaneous burn wounds as first degree (superficial; limited to epidermis), second degree (partial-thickness), and third degree (full-thickness). Second-degree burns are further subdivided into superficial ( Fig. 88.1 ) and deep variants. Burns involving deeper structures such as muscle are sometimes referred to as fourth-degree burns. However, a definitive determination of wound depth may not be possible for the first 24 to 72 hours because of vascular occlusive changes.

At sites where the dermis is thinner (ears, volar forearms, medial thighs, perineum), burns may be deeper than the initial presentation might suggest; this is also the case in the comparatively thinner skin of children and the elderly. Wounds that appear dull red from entrapment of clot (denatured hemoglobin) imply full-thickness injury .

The severity of burn injuries is based upon depth and BSA involvement. BSA is estimated in adults by the “rule of nines” ( Fig. 88.2 ). This formula cannot be applied to children, since the head accounts for ~19% BSA in a 2-year-old, 15% in a 7-year-old, and 13% in a 12-year-old. Lund & Browder charts are useful for more accurate assessment of BSA involvement . Initial evaluation should address airway and circulatory status; associated inhalation injury is seen in up to 25% of burn patients. Cardiovascular evaluation must address the issue of hypovolemic shock, regardless of burn severity. Urine output must be monitored because of the significant fluid loss and rhabdomyolysis that may compromise renal function .

Pathology

Pathologic features of thermal burns are summarized in Table 88.3 .

Differential diagnosis

The differential diagnosis of heat injury is listed in Table 88.1 . Although there is considerable overlap in clinical features, an important distinction is the degree of neurologic compromise. The most important diagnostic issue with thermal burns is the depth of the injury (see Table 88.3 ).

Treatment

Management of heat-related injuries involves removal from the hot environment, rest, rehydration, restoration of electrolyte balance, and evaluation of involved systems ( Table 88.1 ; see Atha for more details).

Initial management of burn victims includes assessment of cardiopulmonary status as well as the extent and depth of the burn. Information regarding resuscitation of burn victims is beyond the scope of this text, but can be found in references , and . For first- and second-degree burns, the burn wound itself should initially be rinsed with cold running water for 20 minutes in order to ease pain, reduce heat, and reduce burn depth . Then the wound should be gently cleansed to remove any foreign material. The next step is prevention of infection, followed by creation of a proper healing environment. Topical anti­microbial agents shown to be effective in burn wound care include silver sulfadiazine, mafenide acetate, and silver nitrate. Silver sulfadiazine has gained wide acceptance for both pediatric and adult burn treatment, but it is known to be cytotoxic and percutaneous absorption can lead to leukopenia. Silver sulfadiazine also produces a pseudoeschar that may interfere with burn depth assessment and prolonged application may lead to localized argyria. Some experts therefore prefer mafenide acetate.

While superficial wounds may require minimal additional therapy , deeper burn wounds need more aggressive therapy, with the standard approach being serial excision and autografting (if there are sufficient donor sites). Third-degree burns are excised early, with indeterminate and deep second-degree wounds delayed until maximum depth and extent are known. Biologic dressings (e.g. pig skin, human allograft) were popular for several years, but have been largely displaced due to higher infection risk and poorer healing. Skin substitutes such as acellular human dermal matrix (Alloderm®), bilaminar bovine collagen–shark chondroitin sulfate (Integra®), and cultured epithelial autografts are increasingly being utilized (see Ch. 145 ).

Introduction

Chronic exposure to low levels of infrared heat can lead to the characteristic reticulated cutaneous pattern of erythema ab igne (EAI), with subsequent risk of malignant degeneration.

History

EAI, once a very common entity, was first described in the UK as a result of standing near stoves fired with peat. In the southern US, the custom of sitting around pot-bellied stoves to keep warm while socializing also led to its development. Although the advent of central heating in much of the industrialized world has led to a dramatic decline in incidence, creative cultural and therapeutic applications of various heating devices continue to induce EAI .

Epidemiology

In the past, EAI was seen up to 10 times more frequently in women than in men. The vast majority of those affected were middle-aged or older. Risk factors include lack of central heating, occupations with close heat exposure, and medical conditions with symptoms relieved by heating or associated with decreased sensation. More recently, reports of EAI due to laptop computers have appeared, including in teens engaged in prolonged gaming .

Pathogenesis

Long-term exposure to heat below the threshold for thermal burn is the primary etiologic factor in EAI. The precise pathophysiology is unknown, but the clinical pattern corresponds with the dermal venous plexus. Repeated exposure to heat below 45°C (113°F) produces reticulated erythema followed by hyperpigmentation in the same pattern . Heat sources reported to cause EAI are found in Table 88.4 .

Clinical features

The initial presentation is transient macular erythema in a broad reticulated pattern that easily blanches. The overall size and shape often approximates that of the heat source. With recurrent heat exposure, the erythema evolves into a dusky hyperpigmentation; lesions become fixed and are no longer blanchable ( Fig. 88.3 ). Epidermal atrophy may overlie the reticulated pigmentation. Later-stage lesions can become somewhat keratotic and bullae may appear. Lesions are characteristically asymptomatic, although a slight burning sensation is sometimes noted .

Once the heat source is identified, it is important to determine if it is being used to relieve pain and, if so, the cause of the pain. A lumbo­sacral location usually points to musculoskeletal disease or, less often, bone metastases. EAI of the abdomen, flank, or mid back may reflect an attempt to relieve pain from inflammation (e.g. pancreatitis, peptic ulcer disease) or malignancy (e.g. pancreatic, gastric). Symptoms of pain should prompt a thorough review of systems and consideration of a search for occult disease. An inquiry into occupation and hobbies is also important, as EAI can develop in exposed areas, e.g. the forearms of bakers, the face or arms of glass blowers and foundry workers, and the anterior thighs or abdomen in those with prolonged use of laptop computers .

The possible development of cutaneous squamous cell carcinoma (SCC) or Merkel cell carcinoma represents the major long-term risk. The latent period may be 30 years or more. Apparently, the risk of developing SCC is highest with hydrocarbon-fueled heat exposure, e.g. “peat fire cancers” on the shins of women, Japanese “Kairo cancers” and Tibetan “Kangri ulcers” due to coal-fired clothing warmers, and Chinese “Kang cancers” from sleeping on coal fire-heated bricks .

Pathology

The earliest histopathologic changes include epidermal atrophy, vasodilation, and dermal pigmentation (both melanin and hemosiderin) ( Fig. 88.4 ). As lesions progress, the epidermal atrophy becomes more pronounced, with flattening of the rete ridges. Focal hyperkeratosis and dyskeratosis are noted along with squamous atypia. Basal cell vacuolization has been reported and the dermal–epidermal junction may exhibit interface dermatitis. The dermis appears thinned and sometimes edematous, with accumulation of abnormal elastic tissue and pigment as well as ectatic capillaries. Dermal capillaries may exhibit enlarged endothelial cells with hyperchromatic nuclei. Later lesions may also show basophilic degeneration of connective tissue. Hemosiderin deposition and prominent telangiectasias are seen most often in leg lesions. Ultrastructural evaluation also shows increased melanocyte dendritic processes, suggesting melanocyte activation .

Differential diagnosis

EAI needs to be distinguished from livedo reticularis, which is a temperature-sensitive vasculopathy that favors the extremities but only occasionally develops associated hyperpigmentation (see Ch. 106 ). Cutis marmorata and cutis marmorata telangiectatica congenita are less commonly considered in the differential diagnosis of EAI. The presence of telangiectasias along with atrophy and hyperpigmentation raises the possibility of poikiloderma and its various causes, e.g. cutaneous T-cell lymphoma (see Ch. 120 ), dermatomyositis (see Ch. 42 ), several genodermatoses (see Ch. 63 ).

Treatment

Management consists primarily of removal of the offending heat source. The epidermal atypia is comparable to that of actinic keratoses, and anecdotally it has been treated successfully with topical 5-fluorouracil. As mentioned above, the use of heat to treat symptoms of pain should prompt an evaluation to determine its etiology .

Introduction

The radiologic literature is replete with reports of superficial to full-thickness thermal or electrical burns occurring during MRI. Risk factors for MRI burns are listed in Table 88.5 . In addition, there are reports in the radiologic and dermatologic literature of ulcerations on the back following repeated fluoroscopy .

Pathogenesis

Although the precise cause of MRI burns is unknown, the presence of both pulsed radiofrequency and pulsed magnetic gradient fields is thought to play a role. If an electrically conductive loop is formed between the patient and an electrode, patient and wiring, or even small areas of skin–skin contact, current can be produced by the changing magnetic flux, causing a thermal or electrical burn. Resistance at the skin surface may create a thermal injury, while contact with wiring in a capacitative coupling may create electrical injury. Alternatively, the burn may result from formation of a resonant conducting loop with an extended wire creating a resonant antenna, heating maximally at the antenna tip .

The mechanism behind fluoroscopy-induced radiodermatitis is related to the dose of radiation that is delivered. Repeated procedures are notorious for increasing the risk . Patients with diabetes mellitus, obesity, autoimmune connective tissue diseases (e.g. systemic sclerosis) or genetic defects involving repair of radiation-induced injury, as well as individuals receiving chemotherapy, appear to be more prone to developing this complication at lower doses of radiation .

Clinical features

Thermal burns appear soon after MRI, and may be partial- to full-thickness (see Table 88.3 ). The shape and size of the burns are determined by the conductor causing the injury (e.g. circular burns under ECG electrodes; figurate burns conforming to the shape of metallic wires or tattoo pigment deposition) .

Fluoroscopy-induced radiation dermatitis may be acute, but, as time passes and the acute injury resolves, the patient may continue to develop further changes, including epilation of hair, desquamation, permanent erythema, and eventual ulceration ( Fig. 88.5 ) . The left upper back is a characteristic location for patients with cardiovascular disease who have had cardiac catheterizations with attempts at revascularization (e.g. angioplasty, stent placement) .

Differential diagnosis

Because of the proximity of the MRI event to the detection of a burn injury, the diagnosis is generally straightforward. However, in the case of a tattoo burn, allergic contact dermatitis or foreign body granuloma formation within the tattoo may be considered. Timing of the event plus the sensation of a burn rather than pruritus should allow a distinction.

The differential diagnosis of fluoroscopy-induced disease includes fixed drug eruptions, contact dermatitis, herpes virus infection, impetigo, and spider bites.

Treatment

Prevention of this injury by avoiding risk factors is ideal. However, when burns occur, they should be managed as any other thermal burn, or, in the case of fluoroscopy-induced injury, by limiting the dose delivered.

Introduction

Automobile airbags provide additional crash protection, reducing driver and passenger fatalities by up to 30%. Although patented in 1953, US manufacturers only began installation of airbags in the mid-1970s. European airbag installation began in 1981. The US Federal Motor Vehicle Safety Standard 208 was amended in 1984, requiring that all vehicles made after 1989 have passive restraints. Further revisions in 1998 made dual front seat airbags mandatory. Despite the beneficial effect, numerous injuries have resulted from airbag deployment, including burns, abrasions, and lacerations .

Pathogenesis

Airbag activation consists of detection, inflation, and deflation phases. The sudden deceleration caused by impact triggers sensors in the front bumper to fire a sodium azide canister inside the nylon rubber bag. The sodium azide ignites with an explosive release of hot nitrogen gas which inflates the bag in about 10 milliseconds at speeds exceeding 160 km/h. The hot nitrogen gas and other by-products are then vented out the upper sides of the bag away from the occupant, thus deflating the bag. Vented aerosol contains nitrogen, carbon mono- and dioxides, sodium hydroxide, ammonia, nitric oxide, metallic oxides and other trace gases, creating a corrosive environment. Friction and pressure from the bag, heat from the bag and gases, and contact with the corrosive aerosol may produce injury .

Clinical features

The cutaneous injuries produced by airbag deployment are summarized in Table 88.6 . Chemical burns occur rarely, but appear to be a result of skin exposure to small amounts of the corrosive alkaline aerosol. The aerosolized particles need to dissolve in a water layer such as tears or sweat before creating a corrosive injury. Of note, alkali burns of the skin may continue to deepen and extend over time, unless all the corrosive chemical is washed away .

Differential diagnosis

The pattern of injury and history of airbag deployment makes the diagnosis obvious. However, it is important to determine whether a burn injury is purely thermal or if it has a chemical component. Assessment of tissue pH and monitoring for continued extension of the burn help determine whether an alkali injury exists.

Treatment

Prevention is, of course, the most effective approach. Newer airbag designs include repositioning the exhaust vents in order to direct the escape of hot gases away from areas of potential skin contact. Seats should be positioned as far back from the airbag module as possible. Children too small to benefit from the adult three-point restraint should not be in the front passenger area. Children in any type of car seat or booster should never be put in the front seat. When a thermal or frictional injury occurs, local wound care and protection from secondary infection usually suffice.

Alkali burns require copious irrigation to dilute the corrosive substance. Acidic neutralization is contraindicated because of possible extension of injury by the resulting exothermic reaction. When the tissue pH is normal, local wound care is adequate.

Introduction

Exposure to cold environments, whether during occupational or recreational activities, poses a risk of cold-related injury. Prolonged exposure may lead to hypothermia, frost-nip, or frostbite. Hypothermia, i.e. a decline in core temperature below 35°C (95°F), is a systemic process with minor cutaneous features and therefore will not be discussed in detail.

History

Cold injury predates recorded history – the quest for clothing, shelter, and fire as protection from the elements must have preoccupied prehistoric humans. Mass casualties from cold injury have historically been seen most often in military conflicts. However, as interest in outdoor activities and the number of homeless individuals have risen, there has been increased exposure to cold among the general population .

Epidemiology

A 10-year retrospective assessment (1986 to 1995) of cold injury in members of the British Antarctic Survey found an incidence of 65.6 per 1000 per year seeking medical attention. Ninety-five percent had frostbite, 3% hypothermia, and 2% cold water immersion foot. Superficial frostbite was the most common injury (74% of cases), with the face (nose) and ears being the most frequent sites of involvement. Seventy-eight percent of the victims were injured during recreational activities. Although temperature and wind chill had no influence on severity of injury, the prevalence of cold injury increased with falling temperature, with a maximum prevalence at −25°C to −30°C (−13°F to −22°F). A major risk factor was prior cold injury .

In addition to homelessness and previous cold injury, risk factors for frostbite include altered mental status, alcohol or illicit drug use, old age, circulatory impairment, smoking, dehydration, vehicular trauma, and high altitude .

Pathogenesis

The underlying pathophysiology of frostbite is a combination of freezing, vascular insufficiency (constriction and occlusion), and damage due to inflammatory mediators. As extremities cool, the “hunting response of Lewis” (alternating vasoconstriction and vasodilation) occurs, ending with vasoconstriction. This tends to conserve the core temperature at the expense of the extremity, which shifts toward ambient temperature. The head does not exhibit a vasoconstrictor response, except for the nose and ears. The trunk surface may cool slightly, but the core temperature is maintained. Frostbite is therefore unusual on the trunk or head (except the nose and ears), unless there is direct contact with ice or a refrigerant. The pathophysiologic stages of frostbite are summarized in Table 88.7 , along with key clinical features .

Clinical features

Frostbite has been divided into four categories of severity, analogous to burn injuries. These are only recognizable upon rewarming. Frost-nip (first-degree frostbite) presents with erythema, edema, cutaneous anesthesia, and transient pain ( Fig. 88.6A ). Full recovery is expected, with only mild desquamation. Second-degree frostbite is characterized by marked hyperemia, edema and blistering, with clear fluid in the bullae ( Fig. 88.6B ). Healing occurs, but many patients have long-term sensory neuropathy, often with significant cold sensitivity.

Third-degree frostbite consists of full-thickness dermal loss, with hemorrhagic bulla formation or development of waxy, dry, mummified skin. The latter features are poor prognostic indicators for tissue loss. Fourth-degree frostbite is a full-thickness loss of the entire part, with skin, muscle, tendon and bone damage. Injuries of this severity lead to amputation . Some authors advocate a simpler classification consisting of superficial or deep injury, citing better prognostic accuracy.

Pathology

Superficial dermal edema and subepidermal bulla formation are typical findings in frostbite. Vascular permeability leads to hemorrhage that is most pronounced in deep injury. The epidermis and involved dermis become necrotic, with an inflammatory infiltrate and granulation tissue at the junction with normal tissue .

Differential diagnosis

Frostbite injuries should be readily recognizable, given an exposure history and typical presentation. A greater diagnostic challenge is determining the depth of the injury (see above). One possible diagnosis in the differential is cold water immersion foot (see Table 88.9 ).

Treatment

Fundamental therapeutic goals in frostbite are rapid rewarming, prevention of further cold exposure, and restoration of circulation. Once the patient is in a setting in which re-freezing cannot occur, rapid water bath rewarming is indicated. The water bath temperature should be about 37–39°C (99–102°F). Rubbing the frozen extremity with ice, using dry heat, and slow rewarming are all contraindicated. In the hypothermic patient with frostbite injury, it is important to complete fluid resuscitation and core rewarming before limb rewarming, to prevent sudden hypotension and shock. Routine wound care, protection of the frostbitten part, and tetanus prophylaxis should then follow. Radiologic evaluation (MRI, bone scan, plain films) may help determine extent of injury and prognosis. Nowadays, triple-phase bone scans are considered the standard of care for assessing tissue viability during the initial days following injury .

Additional therapeutic suggestions have been based on animal studies, case reports, or small series. Because of increased blood viscosity and sludging, thrombolytic therapy (e.g. heparin, tissue plasminogen activator, streptokinase) ± a vasodilator (e.g. iloprost, limaprost) has been suggested. Superficial white (non-hemorrhagic) bullae may be debrided to avoid prolonged exposure to prostaglandins and thromboxanes in blister fluid. Aloe vera, a thromboxane inhibitor, has been shown to be useful as a topical agent in superficial frostbite. The problem of vasoconstriction has been addressed by sympathectomy, with the most impressive effect being prevention of re-injury with repeat exposure to cold conditions. Pentoxifylline has been found to be useful, as have anti-inflammatory agents such as methylprednisolone, methimazole, and aspirin .

Introduction

Pernio is an abnormal inflammatory response to cold, damp, non-freezing conditions . It is most common in areas without central heating.