Acrodermatitis chronica atrophicans: clinical and microbiological characteristics of a cohort of 693 Slovenian patients.

BACKGROUND: Information on large groups of patients with acrodermatitis chronica atrophicans (ACA) is limited. METHODS: We assessed clinical and microbiological characteristics of patients with ACA diagnosed at a single medical centre and compared findings in periods 1991-2004 vs. 2005-2018. The cohort is representative of Slovenian ACA patients. RESULTS: We assessed 693 patients: 461 females and 232 males, with median age of 64 years. Median duration of ACA before diagnosis was 12 months. In all but 2 patients, the skin lesions were located on extremities, more often on the lower (70.0%) than the upper (45.2%), bilaterally in 42.4%. Reddish-blue discoloration, swelling, thinning and wrinkling of skin were present in 95.2%, 28.1%, 46.4% and 20.5% of patients, respectively. Overall, 64.4% of patients reported constitutional symptoms, 23.1% had local symptoms, and 20.8% had symptoms/signs of peripheral neuropathy. Nodules, arthritis, joint deformity, muscle atrophy and paresis were rare (<3%). Borreliae were isolated from 200/664 (30.1%) skin samples; 92.8% were Borrelia afzelii. B. garinii and B. burgdorferi s.s. were more often isolated from the skin of male patients (OR = 4.17) and from those with arthropathy (OR = 11.74). Patients included in the more recent period were older, complained less often of constitutional symptoms but more often of local symptoms, and more often had local swelling but less often skin atrophy and bilateral involvement, probably as a consequence of earlier diagnosis. CONCLUSIONS: ACA, typically caused by B. afzelii, usually affects older women. Clinical presentation depends on the duration of illness and probably on the Borrelia species causing the disease.

Correlation of Reflectance Confocal Microscopy and Dermatopathology Findings in a Case of Acrodermatitis Chronica Atrophicans.

Acrodermatitis chronica atrophicans (ACA) that is characterized by thin, papery dry, translucent, and alopecic patches with visible superficial veins is a late cutaneous manifestation of Lyme borreliosis. Clinical findings, a history of exposure to tick bite, and serology are helpful for the diagnosis of ACA and sometimes a biopsy is performed to rule out other infectious or inflammatory processes. In this study, we report reflectance confocal microscopy (RCM) findings in a case of ACA. RCM examination revealed a flattened surface with broadened skin folds, a flattened dermoepidermal junction with few papillae and less bright basal cells and multiple small bright reflecting spots in the dermis. To the best of our knowledge, this is the first description of the RCM findings in this disorder.

Expanding the clinicopathological spectrum of late cutaneous Lyme borreliosis (acrodermatitis chronica atrophicans [ACA]): A prospective study of 20 culture- and/or polymerase chain reaction (PCR)-documented cases.

BACKGROUND: The diagnosis of acrodermatitis chronica atrophicans (ACA), the late cutaneous manifestation of Lyme borreliosis, can be challenging. Histologic changes in ACA have been described in a few studies from endemic countries, relying on cases documented by serology only. OBJECTIVES: We sought to reassess the clinicopathological spectrum of ACA in a series of thoroughly documented cases. METHODS: Patients prospectively included in a national prospective study were selected on the basis of positive culture and/or polymerase chain reaction of a skin biopsy sample. The diagnosis of ACA was confirmed by reviewing the clinical and serologic data. Histopathological samples were carefully reviewed. RESULTS: Twenty patients were included. Unusual clinical features (ie, numerous small violaceous patches and equidistant small spinous papules with background faint erythema) were observed in 2 patients. Histopathological examination revealed a classic plasma cell-rich perivascular and interstitial pattern with telangiectases in 16 of 25 samples, whereas strikingly prominent granuloma annulare-like or lichenoid features were observed in 4 and 2 of 25 cases, respectively, and discrete nonspecific minor changes in 3 of 25 cases. LIMITATIONS: The small number of patients was a limitation. CONCLUSIONS: Genuine culture- and/or polymerase chain reaction-proven ACA can rarely present as numerous violaceous patches or cluster of spinous papules clinically, and as a granuloma annulare-like or lichenoid dermatosis histologically.

Histopathology and immunophenotype of acrodermatitis chronica atrophicans correlated with ospA and ospC genotypes of Borrelia species.

BACKGROUND: Chronic cutaneous borreliosis (acrodermatitis chronica atrophicans, ACA) is a relatively rare manifestation of borreliosis attributed mainly to Borrelia afzelii. Chronic borreliosis has been associated with ospA and ospC genotypes. Literature on molecular investigations of Borrelia in lesions of ACA is scant. METHODS: Histopathological and immmunohistochemical features in 22 biopsies of ACA (16 patients) were examined. Paraffin-embedded biopsies were analyzed with polymerase chain reaction (PCR) assays targeting ospA and ospC genes, sequencing and phylogenetic analysis. RESULTS: Genotyping of ospA identified B. afzelii, serotype 2, in 12 of 16 patients. ospC-PCR was positive in seven patients revealing genotypes Af5 (n = 4), Af2 (n = 2) and Af6 (n = 1). Histopathologically, interstitial granulomatous infiltrates (CD68 positive) were common, combined with thickened collagen bundles and band-like infiltrates of CD4 positive T lymphocytes. Plasma cells were sparse/absent in 9 of 22 specimens even on staining with CD138. On CD34-staining, interstitial fibroblasts were often reduced akin to the situation in morphea. CONCLUSIONS: With assays targeting ospA and ospC genes we confirmed from paraffin-embedded biopsies that B. afzelii, serotype 2, osp C groups Af5, Af2 and Af6 is the main cause of ACA. Specimens commonly showed a combination of band-like T-cell-rich infiltrates with interstitial granulomatous features, a pattern previously under-recognized in ACA. This finding was particularly typical for lesions infected with ospC genotype Af5.

Acrodermatitis chronica atrophicans with pseudolymphomatous infiltrates.

In this study, we describe the clinicopathologic features of pseudolymphomatous infiltrates found within lesions of acrodermatitis chronica atrophicans (ACA). We studied 11 patients (10 females, 1 male, age range 60-88 years). The diagnosis of ACA in all cases was confirmed by clinicopathologic correlation and positive serology for Borrelia. Histopathologic examination revealed prominent, pseudolymphomatous inflammatory cell infiltrates in all cases, with 2 distinct patterns. Eight of 11 cases showed a band-like lymphocytic infiltrate, exocytosis of lymphocytes and a fibrotic papillary dermis, similar to features seen in mycosis fungoides. The other 3 cases showed dense, nodular-diffuse dermal infiltrates with many plasma cells and without germinal centers. The plasma cells expressed both kappa and lambda immunoglobulin light chains with a polyclonal pattern in all 3 cases. In conclusion, ACA may present with pseudolymphomatous infiltrates showing both a T-cell and, less frequently, a B-cell pattern. These lesions need to be distinguished from a cutaneous lymphoma. In the context of the knowledge of Borrelia-associated cutaneous lymphomas, follow-up seems advisable in these cases.

The expanding spectrum of cutaneous borreliosis.

The known spectrum of skin manifestations in cutaneous Lyme disease is continuously expanding and can not be regarded as completed. Besides the classical manifestations of cutaneous borreliosis like erythema (chronicum) migrans, borrelial lymphocytoma and acrodermatitis chronica atrophicans evidence is growing that at least in part also other skin manifestations, especially morphea, lichen sclerosus and cases of cutaneous B-cell lymphoma are causally related to infections with Borrelia. Also granuloma annulare and interstitial granulomatous dermatitis might be partly caused by Borrelia burgdorferi or similar strains. There are also single reports of other skin manifestations to be associated with borrelial infections like cutaneous sarcoidosis, necrobiosis lipoidica and necrobiotic xanthogranuloma. In addition, as the modern chameleon of dermatology, cutaneous borreliosis, especially borrelial lymphocytoma, mimics other skin conditions, as has been shown for erythema annulare centrifugum or lymphocytic infiltration (Jessner Kanof) of the skin.

Acrodermatitis chronica atrophicans in children: Report on two cases and review of the literature.

Acrodermatitis chronica atrophicans is a late manifestation of European Lyme borreliosis and is characterized by high levels of borrelial IgG antibodies, slowly expanding skin redness usually beginning on distal parts of extremities, and corresponding histologic findings. It very rarely develops in children. The main prerequisite for the diagnosis is clinical suspicion. In the present article we report on two children with acrodermatitis chronica atrophicans and on the findings of a PubMed literature search on acrodermatitis chronica atrophicans in childhood, published in the past three decades.

Lyme borreliosis treatment.

Lyme borreliosis is the most common human tick-borne illness in the Northern Hemisphere. The causative agent is the spirochete Borrelia burgdorferi species complex, and the hard-shell ticks of the genus Ixodes is responsible for pathogen transmission from animals to humans. The incidence of the disease is increasing year by year and although lyme disease is not fatal, it can affect the skin, heart, nervous, and musculoskeletal system with an impairment of quality of life. The appropriate diagnosis of lyme disease should be promptly treated by antibiotics to prevent late stage of the disease. The choice of antibiotics depends on many factors such as the stage of the disease, the drug efficacy, adverse effects, type of delivery, duration of treatment, and cost. Treatment failure occurs as a result of many reasons, re-infection is possible. The recommended treatment schedule in the Czech Republic is presented.

Tatami Mats: A Source of Pitted Keratolysis in a Martial Arts Athlete?

Dear Editor, Pitted keratolysis (PK), also known as keratosis plantaris sulcatum, is a non-inflammatory, bacterial, superficial cutaneous infection, characterized by many discrete superficial crateriform ''pits'' and erosions in the thickly keratinized skin of the weight-bearing regions of the soles of the feet (1). The disease often goes unnoticed by the patient, but when it is noticed it is because of the unbearable malodor and hyperhidrosis of the feet, which are socially unacceptable and cause great anxiety to many of the patients. PK occurs worldwide, with the incidence rates varying based on the environment and occupation. The prevalence of this condition does not differ significantly based on age, sex, or race. People who sweat profusely or wash excessively, who wear occlusive footwear, or are barefoot especially in hot and humid weather are extremely prone to this condition (2). Physicians commonly misdiagnose it as tinea pedis or plantar warts. Treatment is quite simple and straightforward, with an excellent expected outcome if treated properly. We report a case of a 32-year-old male patient with skin changes of approximately one-year duration diagnosed as plantar verrucae, who was referred to our Department for cryotherapy. The patient presented with asymptomatic, malodorous punched-out pits and erosions along with hyperkeratotic skin on the heel and metatarsal region of the plantar aspect of both feet. The arches, toes, and sides of the feet were spared (Figure 1). Except for these skin changes, the patient was healthy and denied any other medical issues. He was an athlete active in martial arts and had a history of sweating of feet and training barefoot on the tatami mat for extended periods of time. The diagnosis of PK was established based on the clinical findings (crateriform pitting and malodor), negative KOH test for hyphae, and a history of prolonged sweating in addition to contact of the skin with tatami mats, which are often a source of infection if hygiene measures are not adequately implemented. Swabs could have been helpful to identify causative organisms, but they were not crucial for the diagnosis and treatment. The patient was prescribed with general measures to prevent excessive sweating (cotton socks, open footwear, and proper hygiene), antiseptic potassium permanganate foot soaks followed by clindamycin 1% and benzoyl peroxide 5% in a gel vehicle twice daily. At the one-month follow-up visit, the skin changes, hyperhidrosis, and malodor were entirely resolved (Figure 2). Pitted keratolysis is common among athletes (3,4). The manifestations of PK are due to a superficial cutaneous infection caused by several bacterial Gram-positive species including Corynebacterium species, Kytococcus sedentarius, Dermatophilus congolensis, Actynomices keratolytica, and Streptomyces that proliferate and produce proteinase and sulfur-compound by-products under appropriate moist conditions (5-7). Proteinases digest the keratin and destroy the stratum corneum, producing the characteristic skin findings, while sulfur compounds (sulfides, thiols, and thioesters) are responsible for the malodor. Athletes and soldiers who wear occlusive footwear for prolonged periods of time or even barefooted people that sweat extensively and spend time on wet surfaces such as laborers, farmers, and marine workers are more prone to this problem (3,4,8-11). Martial arts athletes are at greater risk of skin infections due to the constant physical contact that can lead to transmission of viral, bacterial, and fungal pathogens directly but also indirectly through contact with the mat and the skin flora of an another infected individual. A national survey of the epidemiology of skin infections among US high school athletes conducted by Ashack et al. supported the prevalent theory that contact sports are associated with an increased risk of skin infections. In this study, wrestling had the highest skin infection rate of predominantly bacterial origin (53.8%), followed by tinea (35.7%) and herpetic lesions (6.7%), which is consistent with other literature reporting (12). Being barefoot on the tatami mat in combination with excessive sweating and non-compliance with hygiene measures makes martial arts athletes more susceptible to skin infections, including PK. The diagnosis is clinical, by means of visual examination and recognition of the characteristic odor. Dermoscopy can be useful, revealing abundant pits with well-marked walls that sometimes show the bacterial colonies (13). Cultures, if taken, show Gram-positive bacilli or coccobacilli. Because of the ease of diagnosis on clinical findings, biopsy of pitted keratolysis is rarely performed. Skin scraping is often performed to exclude tinea pedis, which is one of the main differential diagnosis, the others including verrucae, punctate palmoplantar keratoderma, keratolysis exfoliativa, circumscribed palmoplantar hypokeratosis, and basal cell nevus syndrome. If unrecognized and left untreated, skin findings and smelly feet can last for many years. Sometimes, if unrecognized, PK can be mistreated with antifungals, or even with aggressive treatment modalities such as cryotherapy. Appropriate treatment includes keeping feet dry with adequate treatment of hyperhidrosis, preventive measures, and topical antibiotic therapy. Topical forms of salicylic acid, sulfur, antibacterial soaps, neomycin, erythromycin, mupirocin, clindamycin and benzoyl peroxide, clotrimazole, imidazoles, and injectable botulinum toxin are all successful in treatment and prevention of PK (14,15). Topical antibiotics are the first line of medical treatment, among which fusidic acid, erythromycin 1% (solution or gel), mupirocin 2%, or clindamycin are the most recommended (14). As in our case, a fixed combination of two approved topical drugs - clindamycin 1%-benzoyl peroxide 5% gel, had been already demonstrated by Vlahovich et al. as an excellent treatment option with high adherence and no side-effect (16). The combined effect of this combination showed significantly greater effect due to the bactericidal and keratolytic properties of benzoyl peroxide. Additionally, this combination also lowers the risk of resistance of causative microorganisms to clindamycin. Skin infections are an important aspect of sports-related adverse events. Due to the interdisciplinary nature, dermatologists are not the only ones who should be aware of the disease, but also family medicine doctors, sports medicine specialists, and occupational health doctors who should educate patients about the etiology of the skin disorder, adequate prevention, and treatment. Athletes must enforce the disinfecting and sanitary cleaning of the tatami mats and other practice areas. Keeping up with these measures could significantly limit the spread of skin infections that can infect athletes indirectly, leading to significant morbidity, time loss from competition, and social anxiety as well.

Acral manifestations of systemic diseases: Drug-induced and infectious diseases.

Drug reactions and systemic diseases often involve the skin. In particular, most drug-induced reactions and many infectious diseases present with dermatologic manifestations localized acrally, that is on distal portions of limbs (hand, foot) and head (ears, nose). A detailed review of all acral dermatologic signs of drug reactions and systemic diseases is beyond the scope of this paper, although some of these disorders will be discussed specifically here.

Identification of three species of Borrelia burgdorferi sensu lato (B. burgdorferi sensu stricto, B. garinii, and B. afzelii) among isolates from acrodermatitis chronica atrophicans lesions.

In Europe, at least three species of Borrelia are known to be causative agents of Lyme borreliosis: B. burgdorferi sensu stricto, B. garinii, and B. afzelii. Observable differences in the molecular characteristics of the three species have led to speculation that they may also differ in their pathogenic potential and/or tissue tropisms. Several studies have found an association between the chronic skin manifestation of Lyme borreliosis, acrodermatitis chronica atrophicans, and infection by B. afzelii. We sought to find further evidence for such a correlation by studying the genetic profiles of 22 strains of B. burgdorferi sensu lato derived from 21 patients who presented to the University Medical Center, Ljubljana, Slovenia between 1992 and 1995. Strains were isolated in culture from skin biopsies of acrodermatitis chronica atrophicans lesions; in the case of one patient two separate acrodermatitis chronica atrophicans lesions were cultured. All 21 patients had clinically typical lesions with "classic" histopathology and high IgG antibody titers to B. burgdorferi sensu lato. Strains were characterized and typed by 16S ribosomal RNA-specific polymerase chain reaction and determination of their large restriction fragment patterns using pulsed-field gel electrophoresis of MluI-digested genomic DNA. Of the 22 isolates studied, 17 possessed the highly conserved MLa1 pattern characteristic of B. afzelii. The remaining five isolates possessed large restriction fragment patterns that were typical of B. garinii (MLg2, four isolates from three patients) and B. burgdorferi sensu stricto (MLb2, one isolate). The results of 16S ribosomal RNA-specific polymerase chain reaction were concordant with these species designations. These data show that B. afzelii is the predominant, but not the exclusive, etiologic agent of acrodermatitis chronica atrophicans.

Molecular subtyping of Borrelia burgdorferi in erythema migrans and acrodermatitis chronica atrophicans.

Recently, three subtypes of Borrelia burgdorferi have been identified: Borrelia burgdorferi sensu stricto, Borrelia garinii, and the VS 461 group of Borrelia burgdorferi. These subtypes differ by nucleotide sequence variations within several Borrelia burgdorferi specific genes and most likely by their pathogenetic potential. To assess whether different subtypes of Borrelia burgdorferi might be associated with different cutaneous manifestations and clinical courses of Lyme disease, lesional skin biopsies from 35 patients with erythema migrans and 18 patients with acrodermatitis chronica atrophicans were analyzed. A Borrelia burgdorferi specific gene segment encoding a 26-kD protein with subtype specific nucleotide sequence variations was amplified by a nested polymerase chain reaction technique. For molecular subtyping, the products were transcribed into complementary RNA. Upon polyacrylamide gel electrophoresis, complementary RNA molecules separate into several metastable conformational forms resulting in patterns of bands highly specific for the nucleotide sequence of the transcribed molecules. In biopsy specimens of erythema migrans, the VS 461 subtype was detected in 28 of 35 and the Borrelia garinii subtype in six of 35 cases. In one of 35 cases of erythema migrans Borrelia burgdorferi sensu stricto as well as Borrelia garinii was detected. In contrast, in all 18 biopsies of acrodermatitis chronica atrophicans, only the VS 461 subtype was identified. This subtype is rarely found in the USA, where acrodermatitis chronica atrophicans is almost unknown. These data indicate that acrodermatitis chronica atrophicans might be closely associated with the VS 461 group of Borrelia burgdorferi.

Viral diseases of the skin, 1975: a 25-year perspective.

Most of the major advances in modern virology during the past 25 years have been due principally to the development of refined laboratory techniques and tools and have provided a fund of new knowledge and information about the nature of viral infection and pathogenesis. One group of viruses of interest to dermatologists, the herpesviruses, is undergoing intensive biochemical investigation to determine whether it is carcinogenic. As a result of the success of the World Health Organization's campaign to eradicate smallpox, it is predicted that by the end of 1976, smallpox will have been eradicated. Other viruses of dermatologic interest which are now being studied include the agents of warts, molluscum contagiosum, cat-scratch disease, and enteroviruses. Current research in the field of viral chemotherapy may provide the basis for successfully treating these diseases in the future.

Zinc deficiency in two infants during total parenteral alimentation for diarrhea.

Zinc deficiency was observed in two infants receiving total parenteral alimentation for chronic diarrhea. An acrodermatitis enteropathica-like rash occurred in both of the infants. Staphylococcus aureus was cultured from the rash. Treatment with zinc resulted in rapid cure of the rash and a subsidence of other signs consistent with zinc deficiency.

Evidence for the involvement of different genospecies of Borrelia in the clinical outcome of Lyme disease in Belgium.

In addition ot Borrelia burgdorferi, recognized as the aetiological agent of Lyme disease, at least two separate genospecies have recently been described. A relationship between infection by strains belonging to different genospecies and clinical outcome has been suspected. In this paper, 9 cases of Lyme arthritis were attributed to infection by B. burgdorferi sensu stricto, 18 cases of neuroborreliosis to B. garinii and one case of acrodermatitis chronica atrophicans to a strain of B. afzelii. These conclusions were based on the preferential reactivity of sera with antigens of given strains in Western blots and on residual reactivity after absorption of sera with antigens of representative strains. No conclusion could be reached concerning sera of 10 patients with erythema migrans.

Long-term prognosis in patients treated for erythema chronicum migrans and acrodermatitis chronica atrophicans.

OBJECTIVE: To determine whether Lyme borreliosis persisted or had recurred in patients treated for erythema chronicum migrans and acrodermatitis chronica atrophicans. DESIGN: Retrospective follow-up study. Mean time between treatment and follow-up study was 8.8 years (SD, 66.6 years). SETTING: Department of dermatology. PATIENTS: Patients (N = 52) treated from July 1964 to October 1992 for erythema chronicum migrans (ECM; n = 44) or acrodermatitis chronica atrophicans (ACA; n = 8). Fifty-two of the 56 successfully contacted and registered patients agreed to participate, for a response rate of 93%. MAIN OUTCOME MEASURES: Signs and symptoms of Lyme borreliosis; serum antibodies to Borrelia burgdorferi. RESULTS: The interval from the time of diagnosis to study entry was 0.8 to 28.7 years (mean, 8.2 years). No symptoms or signs of active Lyme borreliosis were observed in the 52 patients. Antibodies to B burgdorferi were found in the ECM group in 1 of the 23 patients who received a recommended treatment and 2 of the 21 patients who received other treatments; antibodies were found in the ACA group in all 5 adequately treated patients who received a recommended treatment and in 1 of the 3 patients who received other treatments. CONCLUSIONS: There was no association between serologic results and type of treatment or between serologic results and complaints or symptoms at the time of the study in either of the patient groups. The prognosis in most patients with Lyme borreliosis is excellent.

Lyme borreliosis.

Lyme borreliosis is a cutaneous-systemic infection that is generally transmitted by a hard-bodied tick and caused by some species of Borrelia, Borrelia burgdorferi (sensu stricto), B. garini, and B. afzelii. Lyme borreliosis is a widespread disease, present in all continents. It can be divided into an early disease, corresponding to the primary stage, and a late disease, including the secondary and tertiary stages. The typical cutaneous lesions are erythema (chronicum) migrans, lymphadenosis benigna cutis, and acrodermatitis chronica atrophicans. The course of Lyme borreliosis depends on the timeliness of both diagnosis and antibiotic treatment.

Isolation of Borrelia burgdorferi sensu lato from a fibrous nodule in a patient with acrodermatitis chronica atrophicans.

A 66-year-old woman presented with a 2-year history of acrodermatitis chonica atrophicans of her left hand and associated fibrous nodules. In addition to skin changes she experienced profound fatigue, and pains and swelling of the left elbow and dorsum of the left hand. On clinical examination, typical livid-red discoloration of the skin distally from the left elbow was evident with atrophy on the dorsum of the hand. Nodules with diameters from 0.5 to 2 cm were present around the olecranon and along the ulnar region. The indirect immunofluorescent assay (IFA) without absorption in serum revealed negative borrelial IgM and positive IgG (1:512) antibody titres. Histological findings on tissue specimens were compatible with acrodermatitis chronica atrophicans and fibrous nodule tissue, respectively. Cultures in MKP medium of biopsy specimens from the involved skin and from one of the nodules were positive. Both isolates were identified as B. afzelii with concordant protein and plasmid profiles. The patient received a 3-week course of ceftriaxone (2 g daily, i.v.). Her condition progressively improved: pains and swelling vanished by the end of treatment, fibrous nodules diminished and skin lesions gradually began to fade. According to a MEDLINE literature search this is the first report of the isolation of B. burgdorferi sensu lato from a fibrous nodule in a patient with acrodermatitis chronica atrophicans.

Characterization of Borrelia burgdorferi sensu lato strains isolated from human material in Slovenia.

The aim of the study was to assess genotypic and phenotypic diversity among a large number of clinical isolates of Borrelia burgdorferi sensu lato obtained from patients in Slovenia. Plasmid profiles and species identification were determined by PFGE, protein profiles by SDS-PAGE. Of 706 B. burgdorferi sensu lato human isolates 599 (85%) were found to be B. afzelii, 101 (14%) B. garinii and six (1%) B. burgdorferi sensu stricto. The vast majority of strains (605; 86%) were isolated from skin, 58 (8%) from blood, and 43 (6%) from CSF. When analysed by RFLP, B. afzelii strains were unique, while heterogeneity was found within B. garinii and B. burgdorferi sensu stricto species. An unusual plasmid content was found in 52/706 (7%) isolated strains, more often in B. garinii than in B. afzelii strains. A plasmid dimer was found in B. afzelii and B. garinii strains, whereas multiple copies of the large plasmid were associated nearly exclusively with B. garinii strains. Analysis of protein profiles revealed that OspA and OspB are expressed more often by B. afzelii strains, and OspC by B. garinii strains. Heterogeneity of Borrelia strains may play a significant role in the virulence and pathogenesis of the infection. Differences in antigenic components have an important impact on serological testing and vaccine development.