Papular urticaria: a histopathologic study of 30 patients

Eosinophilic Dermatosis of Hematologic Malignancy: Emerging Evidence for the Role of Insect Bites-A Retrospective Clinico-Pathological Study of 35 Cases

Background/Objectives: Eosinophilic dermatosis of hematologic malignancy (EDHM) is a rare cutaneous disorder associated with various hematologic malignancies, most commonly chronic lymphocytic leukemia. Detailed clinicopathologic studies of EDHM are lacking and the pathogenesis remains enigmatic. Initially thought to be a hypersensitivity reaction to insect stings, subsequent reports have challenged this understanding. The prognostic implications of EDHM remain unclear. Methods: A retrospective clinicopathologic study was performed on patients diagnosed with EDHM. Hematologic and dermatologic data were reviewed. Histologic specimens were re-evaluated and lesions were classified into acute/subacute, fully developed, and chronic/regressing. Results: The study included 35 patients. In 80% of these patients, EDHM was diagnosed after the hematologic disorder. Approximately 45% of the cohort experienced hematologic disease progression or relapse, while 65% required therapeutic intervention during the course of their hematologic disease. In total, 15/19 CLL patients had non-mutated IgHV, a marker of a more aggressive hematologic disease course. Dermatologic lesion morphology was heterogeneous, with most lesions occurring on exposed areas, and a significant 94% of patients demonstrated lesion seasonality. Histopathologic findings were consistent with features typically associated with insect bites. In addition, examination of lesions at different chronological stages revealed substantial similarities with Wells syndrome. Conclusions: Our findings support the potential role of insect bites in triggering EDHM in the context of adaptive immune dysfunction. EDHM may be associated with a more aggressive disease course or may be a marker of disease progression. The observed co-occurrence of features typical of Wells syndrome in EDHM patients suggests that these conditions are part of a spectrum of disorders that vary in clinical expression.

Eosinophilic dermatosis of hematologic malignancy in patients with chronic lymphocytic leukemia/non-Hodgkin's B lymphoma: a single center prospective clinico-pathological study

Background

The pathogenesis of eosinophilic dermatosis of hematologic malignancy (EDHM) is poorly understood. Previously thought to be a hypersensitivity reaction to insect bites, immune dysregulation and cytokine imbalance are now thought to be responsible. Its prognostic significance is unclear.

Objective

To describe the clinical, pathological and immunological findings in a series of oncohematological patients with EDHM.

Methods

An observational prospective cohort study of oncohematological patients receiving a diagnosis of EDHM between April 2017 and December 2018.

Results

A total of 15 patients with EDHM (10 females and 5 males) were identified among 422 oncohematological patients. Disease presentation varied from firm erythematous papules to more polymorphic presentations. The lesions were most prevalent on the exposed sites, 8/15 patients recalled an insect bite. Lesion seasonality was reported in 13/15 patients. IgE levels were elevated in six patients, circulating IL-4 and IL-5 were within a normal range. Twelve out of 15 patients developed skin manifestations after chemotherapy. The infiltrate could be eosinophil-rich or lymphocytic-rich. Interestingly, the histopathologic findings were in accordance with arthropod bites.

Conclusion

A role for insect bites in EDHM is supported by our findings. EDHM may be related to aggressive hematologic disease.

Annular urticarial lesions

Annular urticarial configurations are often associated with acute and chronic urticaria. Such lesions may be short-lived, migratory, transient, pruritic, and resolving with no residual evidence, making the diagnosis of urticaria an obvious one. Annular urticarial lesions can be the presenting signs of various cutaneous and systemic diseases. The differentiation of urticarial lesions may be made by considering the duration of an individual lesion longer than 24 hours, with burning and pain sensation in the lesions or lack of pruritus; skin marks such as postinflammatory pigmentation or purpura after resolution of the lesions; associated scaling or vehiculation in the lesions; systemic symptoms such as arthralgia, fever or fatigue; and several abnormal laboratory findings. The main differential diagnoses of annular urticarial lesions include urticarial vasculitis, autoinflammatory syndromes, hypersensitivity reactions, and connective tissue diseases.

Cutaneous eccrine inflammation and necrosis: review of inflammatory disorders affecting the eccrine apparatus including new associations

Despite being frequently overlooked during the examination of histopathological sections, eccrine sweat glands can offer clues for diagnosing various skin conditions. They provide important functions and can lead to several diseases when inflamed or injured. This review article provides information regarding eccrine physiology as well as well-established and novel entities that occur in association with eccrine gland pathology.

Cellular and Humoral Responses to Cte f 2, a Cat Flea Allergen, in Children with Papular Urticaria

BACKGROUND

Papular urticaria (PU) is a common insect bite skin hypersensitivity in tropical countries. In order to gain insight into its causal allergens, we aimed to evaluate cellular and humoral immune responses to the recombinant salivary antigen Cte f 2 from the cat flea Ctenocephalides felis.

METHOD

Sixty patients with PU and 27 healthy controls were included in this study. Specific IgE, IgG, IgG1, and IgG4 against Cte f 2 and C. felis extract were determined by ELISA. The T-cell response was analyzed using a carboxyfluorescein succinimidyl ester (CFSE)-based dilution assay and Th1/Th2/Th17 cytokine measurements. In addition, a proteomic analysis of IgG and IgE reactive spots of C. felis extract was performed.

RESULTS

The frequency of IgE sensitization to Cte f 2 was similar between patients (36.7%) and controls (40.7%). The specific IgE, IgG1, and IgG4 responses to Cte f 2 and C. felis extract were not significantly different between patients and controls. Among the 3 conditions (i.e., Cte f 2, C. felis extract, and only medium) Cte f 2 was the strongest inducer of CD3+CD4+ proliferation in the patients; however, the mean response was not significantly different from those in controls (Cte f 2: 4.5 vs. 2.5%; p = 0.46). No salivary proteins were identified in C. felis, and most of the spots were identified as muscle-skeletal components (tropomyosin, actin, myosin, and ankirin).

CONCLUSIONS

Cte f 2 induces IgE and IgG production as well as T-cell proliferation in children living in a geographical area where PU induced by a flea bite is common. The use of C. felis extract is not recommended for the study of bite-induced hypersensitivity disease since salivary antigens are not well represented.

Histopathology of Cutaneous Inflammatory Disorders in Children

Inflammatory dermatoses encompass a variety of histologic patterns that affect different portions of the skin. In spongiotic, psoriasiform, lichenoid, pityriasiform, and blistering disorders, there are predominately epidermal and junctional activities with variable superficial dermal inflammation. Hypersensitivity reactions can show either epidermal or mostly dermal changes depending on whether the exposure of the exogenous allergen occurs through an external or internal route, respectively. Exceptions include erythema multiforme and Stevens-Johnson syndrome/toxic epidermal necrolysis, where the etiology is often due to infection or ingested medications, but the histologic features are almost exclusively confined to the epidermis and dermoepidermal junction. Autoimmune disorders are unique in that lesions typically incorporate a mixture of epidermal and dermal inflammatory patterns with periadnexal inflammation, while the vast majority of vasculitis/vasculopathy and alopecia have changes limited to only the vessels and hair follicles, respectively. It is critical to recognize that a relatively limited number of histologic patterns are seen in a large array of clinical entities. Therefore, clinicopathologic correlation and careful examination of histologic details are of the utmost importance when evaluating skin biopsies for inflammatory disorders.

The eyelid sign: a clue to bed bug bites

In pediatric patients, determining the culprit insect in arthropod assaults can be challenging. The patient's history may be vague, the causative insect may not be readily associated with the bites, and the clinical appearance of bites can be variable. Six pediatric patients from the Penn State Milton S. Hershey Medical Center dermatology offices with bed bug bites were identified. All had bites involving the face, trunk, and extremities. Five patients demonstrated papules on one upper eyelid associated with erythema and edema. One patient had papules on both upper eyelids. When an arthropod assault is suspected, the "eyelid sign," i.e., bites involving the upper eyelid associated with erythema and edema, may point to bed bugs.

Leporacarus gibbus infestation in client-owned rabbits and their owner

BACKGROUND

Leporacarus gibbus is a fur mite infesting both laboratory and pet rabbits; infestation is usually subclinical, but in some instances it has been associated with a highly pruritic dermatitis. A zoonotic potential has also been suggested.

ANIMALS

Two pet rabbits, living in the same household, were presented with moderate scaling, erythema, pruritus and alopecia. In both rabbits, the lesions were mainly localized around the neck. A pruritic papular dermatitis was also present on the owner's arms and legs.

METHODS AND RESULTS

Parasitological examination of the rabbits' skin and fur revealed many mites of the species L. gibbus. Skin cytology and fungal culture were both negative for bacteria and fungi. Both rabbits were treated with a single application of a spot-on formulation of 1% moxidectin and 10% imidacloprid, as well as environmental disinfection with a miticide. After treatment, the rabbits improved markedly, and the lesions on the owner's arms and legs disappeared within a week.

CONCLUSIONS AND CLINICAL IMPORTANCE

This is the second description of L. gibbus dermatitis in people. In the present case report, the lesions on the rabbits and their owner were very similar, a pruritic dermatitis with small papules, more evident on the owner's extremities. Due to its zoonotic potential, although uncommon, L. gibbus infestation should be considered as a possible differential in pet rabbits, particularly when owners have a papular eruption.

A histopathologic study of arthropod bite reactions in 20 patients highlights relevant adnexal involvement

BACKGROUND

Insect bites produce diverse skin reactions. Although quite common, the histopathologic features of arthropod assaults have not ever been studied systemically.

MATERIALS AND METHODS

Twenty biopsies from cases, clinically diagnosed as arthropod bite reactions between January 2003 and June 2007 were reviewed retrospectively. The aim of the study was to verify as to whether reliable histopathologic criteria could be established based on the frequency of findings observed.

RESULTS

Epidermal spongiosis (present in 16 of 20 cases), in particular spongiosis of the infundibular epithelium and acrosyringia as well as eosinophilic spongiosis, emerge as relevant diagnostic clues. A moderately dense, superficial and deep infiltrate consisting mainly of lymphocytes and eosinophils was prevalent in the dermis, with eosinophils tending to interstitial and periadnexal distribution. Of note, 19 of 20 (95%) cases revealed periadnexal involvement, whereas 16 of 20 (80%) had the infiltrate extending particularly along the sweat ducts and the coiled glands. In three biopsies, concomitant involvement of sweat glands, hair follicles and sebaceous glands was noted.

CONCLUSION

A practical histopathologic algorithm of arthropod bite recognition is proposed. The involvement of the sweat glands in the pattern of arthropod bite reaction is suggested as a new reliable diagnostic clue.

Prolonged urticaria with purpura: the spectrum of clinical and histopathologic features in a prospective series of 22 patients exhibiting the clinical features of urticarial vasculitis

BACKGROUND

Biopsy specimens of lesions with clinical features of urticarial vasculitis often show a predominantly lymphocytic infiltrate with eosinophils and red blood cell extravasation. Only occasionally is a leukocytoclastic vasculitis encountered, confirming a diagnosis of urticarial vasculitis.

OBJECTIVE

The aim of this study was to assess the clinical presentation and histologic features of patients who meet the clinical criteria for urticarial vasculitis.

METHODS

Patients were recruited who had persistent urticarial lesions individually lasting longer than 24 hours, associated with at least 2 of 3 of the following: pain or tenderness; purpura or dusky changes; and resolution with hyperpigmentation. Patients were interviewed based on a standard questionnaire with regard to their symptoms. Blood tests and chest radiographs were performed to exclude systemic involvement and hypocomplementemia. Skin biopsy specimens were sent for histology and direct immunofluorescence.

RESULTS

Of 22 patients recruited, 19 (86.4%) showed a predominantly lymphocytic infiltrate on histology. Three cases (13.6%) had a neutrophil-predominant infiltrate associated with a leukocytoclastic vasculitis. Twenty (90.9%) had a superficial perivascular infiltrate, and two (9.1%) had a superficial and deep perivascular infiltrate. In all, 21 biopsy specimens (95.5%) showed inflammatory cells within dermal blood vessel walls, obscuring the vessel outline in some. Endothelial cell swelling was seen in 20 biopsy specimens (90.9%), erythrocyte extravasation in 17 (77.3%), nuclear dust in 5 (22.7%), and fibrin extravasation in 2 (9.1%). Multivariate analysis revealed the following features to be independently associated with neutrophil predominance: fulfillment of all 3 minor criteria for urticarial vasculitis-like lesions (P = .007); presence of fibrin on histology (P < .001); presence of nuclear dust on histology (P = .001); hypocomplementemia (P = .001); and anemia (P = .015). There was a trend toward lesions not clearing as readily in the neutrophil-predominant group (P = .071), even with two-modality treatment (P = .089).

LIMITATIONS

Serum immunoelectrophoresis was not done to exclude Schnitzler's syndrome. Electronmicroscopy and cytokine profiling were not performed.

CONCLUSION

Biopsy specimens of lesions with clinical features of urticarial vasculitis reveal that only a minority of patients has leukocytoclastic vasculitis. The majority has a lymphocyte-predominant histology, associated with varying numbers of eosinophils. We favor a lymphocytic vasculitis as a causative explanation in the lymphocyte-predominant group.

Insect bite-induced hypersensitivity and the SCRATCH principles: a new approach to papular urticaria

Insect bites and the associated hypersensitivity reactions known as papular urticaria account for a significant number of all referrals from pediatricians and dermatologists to our pediatric dermatology clinic. Unfortunately, children affected by these eruptions are frequently misdiagnosed and often subject to expensive evaluations including invasive and unnecessary procedures. Here we review the course of 4 children with the typical physical findings and natural history of these reactions. On the basis of our clinical findings and experience with this patient population, we propose a set of principles (termed "SCRATCH") as clinical features to aid clinicians in making an early and accurate clinical diagnosis. We conclude that a more appropriate term for future study and diagnosis of this entity is insect bite-induced hypersensitivity.

Pruritic papular eruption associated with HIV-etiopathogenesis evaluated by clinical, immunohistochemical, and ultrastructural analysis

Pruritic Papular Eruption with Human Immunodeficiency Virus infection (PPE-HIV) is characterized by symmetrically distributed papules with pruritus in the skin of patients suffering advanced HIV infection. Although known since 1985, the etiology of this symptomatic dermatitis is unclear. We set out to characterize the phenotype of the infiltrating cells and the cytokine profile in the lesions, as an attempt to contribute to determining its etiopathogenesis. Clinical data and histological, immunohistochemical, and ultrastructural features of skin biopsies from 20 HIV patients with PPE were studied. The histopathological aspects, cell immunophenotypes, and cytokine expressions in the lesions where quantified and compared to perilesional skin, and to those in the clinically normal skin of HIV patients without PPE-HIV (n=11) and those in normal skin samples from HIV negative individuals (n=10). PPE-HIV occurred mainly in HIV patients with mean CD4+ counts of 124.6 +/- 104 lymphocytes/mm3. Furthermore, their eosinophil counts were significantly increased. The skin lesions were characterized by a predominantly perivascular dermal lymphohistiocytic inflammatory infiltrate. Langerhans cells were normally distributed in the epidermis and seen among the cellular components of dermal infiltrates. The density of CD8+ lymphocytes was elevated and the density of CD4+ cells was reduced in dermal infiltrates. Interleukin 5 was the predominant cytokine in the lesions. Electron microscopic analysis didn't disclose HIV or other infectious agents in the lesions. These results refute the hypothesis of an infectious etiology of PPE-HIV. CD8+ lymphocytes and Langerhans cells seem to have roles in the pathogenesis of PPE-HIV. The increased frequency of IL5 was associated with abundant eosinophils in the lesions, suggesting a type Th2 response in this dermatitis.

The return of the common bedbug

The incidence of skin disease secondary to infestation with the human bedbug, Cimex lectularius, has increased dramatically in the United States and in the United Kingdom. We describe a child with a recurrent pruritic eruption of urticarial, erythematous papules on the face, neck, and extremities. The etiology of her cutaneous lesions was discovered to be a bedbug infestation in the home. The epidemiology, entomology, presentation, and treatment of bedbugs and their bites are discussed.

Immune and histopathologic examination of flea bite-induced papular urticaria

BACKGROUND

Papular urticaria caused by flea bite presents clinical symptoms of hypersensitive reaction accompanied by skin lesions. Diagnostic and therapeutic approaches to the disease often go unrewarded, partly because of our incomplete understanding of the underlying immunopathogenesis.

OBJECTIVE

To characterize the immune response to the flea bite in patients with papular urticaria.

METHODS

This study included 45 randomly selected patients and 17 controls. Cutaneous allergy tests were performed. The histopathologic and immunohistochemical characteristics of cellular infiltrate in skin lesions were established. Immunoblot analysis was used to describe the specific characteristics of flea proteins recognized by IgE and IgG in patients' serum samples.

RESULTS

Cutaneous allergy test results were negative in 87% to 98% of patients and in 88% to 100% of controls. Histopathologic and immunohistochemical studies revealed a predominance of eosinophils and CD4+ T lymphocytes. Immunoblotting did not show significant differences in IgG response between patients and controls. IgE recognition of flea proteins appears to decrease as the disease progresses.

CONCLUSIONS

Our results suggest that the clinical manifestations of papular urticaria are mediated by a complex immune response involving more than one mechanism, with evidence forboth an IgE response and a cell-mediated type IV response.

Arthropods in dermatology

Arthropods are important in medicine for a multitude of reasons. Their bites and stings may induce allergic reactions, ranging from annoying to life-threatening. Many arthropod products are also capable of inciting allergic responses in sensitized persons. In recent years, bites and stings have gained greater attention owing to increased concern about disease transmission. A common hypersensitivity response to arthropod bites, stings, and products is papular urticaria. This eruption occurs primarily in children, who eventually "outgrow" this disease, probably through desensitization after multiple arthropod exposures. Papular urticaria is most often caused by fleas or bedbugs, but virtually any arthropod is capable of inducing such a reaction. Two arthropod classes of medical importance are the Arachnida (spiders, scorpions, ticks, and mites) and the Insecta (lice, fleas, bedbugs, flies, bees, and ants). Animals in these two classes are probably responsible for more morbidity and mortality worldwide than are any other group of venomous creatures. In general, the diagnosis of arthropod bites and stings is dependent on maintenance of a high index of suspicion and familiarity with the arthropod fauna not only in one's region of practice, but also in the travel regions of one's patients. Learning objective At the completion of this learning activity, participants should be familiar with the clinical manifestations caused by a variety of arthropods as well as the treatment and possible sequelae of arthropod attacks.

Papular urticaria and things that bite in the night

Whether we are hiking in the back country or playing in our backyard, we run the risk of exposure to offending arthropods. Papular urticaria is a very common hypersensitivity reaction to the bites, stings, and contact with critters such as mites, ticks, spiders, fleas, mosquitoes, midges, flies, and even caterpillars. Children seem to be at greatest risk, although adults are also vulnerable. The classic presentation of papular urticaria includes recurrent pruritic papules or vesicles and varying degrees of local edema. Severity is often related to the host response to the salivary or contactant proteins. Our understanding of the immune mechanism continues to improve; however, our approach to therapy has remained essentially unchanged. Although this review admittedly reaches beyond papular urticaria, it is with the intention of improving the reader's recognition of the offending arthropods, the characteristics of reactions, and the current therapeutic approaches.

Prevention of acute urticaria in young children with atopic dermatitis

BACKGROUND

There are no published prospective, randomized, double-blind, placebo-controlled studies of urticaria prevention in children.

OBJECTIVE

Our objective was to study the effect of long-term treatment with the H(1)-receptor antagonist cetirizine in the prevention of urticaria in young children with atopic dermatitis.

METHODS

In the prospective, double-blind, parallel-group Early Treatment of the Atopic Child study, 817 children with atopic dermatitis who were 12 to 24 months of age at study entry were randomized to receive either cetirizine, 0.25 mg/kg, or matching placebo twice daily for 18 months and to be followed up for an additional 6 months, during which time the study medication code remained unbroken. During both these double-blind phases of the study, for a total of 24 months, caregivers prospectively recorded all symptoms and events, including hives, in a diary on a weekly basis when the child was well and on a daily basis when a symptom or event was observed. The diaries were reviewed and validated with the investigators at each regularly scheduled study visit.

RESULTS

Acute urticaria occurred in 16.2% of the placebo-treated children and in 5.8% of the children treated with cetirizine (P <.001). The protective effect of cetirizine disappeared when treatment was stopped. In the study population as a whole, urticaria episodes were most commonly associated with intercurrent infection or with food ingestion or direct skin contact.

CONCLUSION

Acute urticaria is common in toddlers with atopic dermatitis and can be prevented with cetirizine in this high-risk population.

Nodular tuberculid: a report of four patients

The tuberculids are hypersensitivity reactions to Mycobacterium tuberculosis (MTB) and include papulonecrotic tuberculid (PNT), lichen scrofulosorum, erythema induratum of Bazin (EIB), and phlebitic tuberculid. Papulonecrotic tuberculid displays papulonecrotic lesions mostly on the extensor surfaces of the limbs. Histopathology shows necrosis, granulomatous inflammation (GI), and occasionally vasculitis, usually in the superficial dermis. Erythema induratum of Bazin shows nodulo-ulcerative lesions on the posterior aspect of the legs. Histopathology reveals a septolobular panniculitis, necrosis, GI, and vasculitis. The Mantoux test is strongly positive and associated tuberculosis (TB) may be present in both conditions. MTB cannot be demonstrated with a Ziehl-Neelsen (ZN) stain or cultured. The polymerase chain reaction has demonstrated MTB DNA in PNT (50%) and EIB (25%). The tuberculids respond to full anti-TB treatment. We document four patients with nodules on the legs in whom the pathologic changes were situated in the deep dermis and adjacent subcutaneous fat. Nodular tuberculid (NT) is regarded as a suitable term for these lesions. All patients were female. Their ages were 19 months, 12 years, 17 years, and 5 years. All patients presented with nodules on the limbs. These nodules were approximately 1 cm in diameter, dull red or bluish-red, and nontender. Ulceration was not present. The number of nodules varied from a few to many. The Mantoux test was strongly positive in all the patients. Associated pulmonary TB was present in two patients. Histopathology showed GI (n = 4), vasculitis (n = 2), and coagulative necrosis (n = 2). A ZN stain was negative in each case. All patients received anti-TB treatment for 6 months [rifampicin (n = 4), isoniazid (n = 4), pyrazinamide (n = 4), and ethambutol (n = 2)]. At 12 months follow-up, skin and pulmonary lesions had resolved in all. Nodular tuberculid should be distinguished from arthropod bites and papular urticaria, dermal erythema multiforme, evolving vasculitis, evolving folliculitis, and erythema nodosum. Histopathologically NT should be distinguished from other causes of granulomatous vasculitis and GI with or without necrosis. In children with nodules on the limbs unresponsive to routine treatment, skin biopsy should be done to exclude NT. Nodular tuberculid represents a hybrid between PNT and EIB with characteristic clinicopathologic features and should be included in the classification of cutaneous TB.

Generalized pruritus without primary lesions. Differential diagnosis and approach to treatment

A 65-year-old man presented with recurrent generalized pruritus and excoriations of many years' duration. He had been treated with antihistamines, topical corticosteroids, and antibiotics for secondary wound infections, but improvement was only temporary. He had also been hospitalized for leg ulcers complicated by cellulitis. Examination revealed multiple oval and linear red papules and nodules measuring 0.5 to 2 cm in diameter. Some of the lesions were eroded and had a central crater and yellowish crust. The patient also had hypopigmented linear scars localized to the posterior scalp, neck, upper back, chest, abdomen, arms, and legs with sparing of the middle and lower back (figures 1 and 2). An ulcer measuring 1.5 x 2 cm that was surrounded by indurated skin was present on the medial aspect of his right ankle. The ulcer was partially covered by yellow exudate. There was no evidence of cellulitis. Liver enzyme, serum creatinine, and thyrotropin levels, as well as a chest roentgenogram, were normal. Wound cultures for bacteria and fungi were nonsignificant. A punch biopsy from a representative lesion showed an abrupt epidermal defect with sparse superficial lymphocytic infiltrate in the dermis. The patient was admitted to the hospital to isolate him from his home environment. He received a 10-day course of systemic cephalexin, topical clobetasol propionate ointment for the affected skin areas, and oral hydroxyzine for pruritus. Ultraviolet light therapy was instituted once daily and was to continue for 2 months. His lesions had improved moderately by the time he was discharged from the hospital. On follow-up 2 weeks later, his lesions were flat and had resulted in hypopigmented scars. Three months later, however, he had persistent, intense pruritus, and new excoriations had developed on his forearms and back. He improved after receiving treatment with oral doxepin hydrochloride.

Bites and stings of the arthropod kind. Treating reactions that can range from annoying to menacing

Bites and stings from arthropods are largely inevitable because of the number of offending species and their distribution throughout our environment. Wasps, bees, ants, mosquitoes, gnats, chiggers, and fleas are found all across the United States. Thus far, Africanized honeybees are limited to southwestern states and fire ants to southern states. Brown recluse spiders are found most often in the Midwest and south central region, but the black widow spider is found in all 48 contiguous states. The dangerous Centruroides species of scorpion live mostly in southern states and California. Fortunately, in most people, bites and stings from arthropods produce only self-limited reactions, which can usually be managed with cold packs, analgesics, and topical agents. In the few encounters that produce serious reactions, prompt diagnosis and appropriate treatment result in a good outcome in nearly all cases. The number of stings and bites can be reduced with use of a few basic avoidance and protection measures.