Acrodermatitis chronica atrophicans (ACA) is a progressive skin condition caused by a Borrelia infection transmitted through tick bites, and it represents one of the latest stages of Lyme disease. Unlike the well-known bull’s-eye rash of early Lyme, ACA develops months to years after the initial infection and slowly destroys the skin, leaving it paper-thin and discolored. It is overwhelmingly a European phenomenon, tightly linked to the Borrelia species that circulate there, and it ranks among the most commonly misdiagnosed conditions in dermatology.
What Causes ACA
ACA is a tick-borne infection. The bacterium responsible belongs to the Borrelia burgdorferi sensu lato complex, and the specific species most strongly linked to ACA is Borrelia afzelii. This species has been isolated and its DNA detected predominantly in the chronic skin lesions of ACA patients.1The Open Dermatology Journal. Atrophosclerodermic Manifestations of Lyme Borreliosis The major tick vector is Ixodes ricinus, the castor bean tick found across much of Europe.2Dermatology and Dermatitis. An Infection of Acrodermatitis Chronica Atrophicans Herxheimer by Borrelia Affzelii
The relationship between ACA and B. afzelii is remarkably tight. Molecular subtyping studies have found that in ACA skin biopsies, a particular Borrelia subtype (known as VS 461, which corresponds to B. afzelii) was identified in all specimens tested, while erythema migrans lesions showed a wider mix of Borrelia species.3PubMed. Molecular subtyping of Borrelia burgdorferi in erythema migrans and acrodermatitis chronica atrophicans This species preference helps explain why ACA is almost exclusively a European disease: B. afzelii circulates in European tick populations but is rarely found in North America, where the dominant species (Borrelia burgdorferi sensu stricto) tends to target joints and the nervous system rather than the skin.
Why the Infection Becomes Chronic
Most people think of Lyme disease as something that either resolves on its own or gets cleared with a round of antibiotics. ACA challenges that assumption. The condition can persist for years, even decades, if untreated. One reason is that the bacteria appear to interfere with the skin’s immune surveillance. Research on chronic Lyme skin manifestations has found a marked reduction in the activity of certain immune cells in the skin, specifically a downregulation of molecules involved in presenting foreign material to the immune system. This impaired capacity to process and clear bacterial material may allow B. afzelii to linger in the skin long after the initial infection.4Clinical Infectious Diseases. Why Is Chronic Lyme Borreliosis Chronic?
The immune system does respond to ACA, but the response is chronic and ultimately destructive to the skin itself. Biopsies of ACA lesions show dense collections of immune cells, including T lymphocytes and plasma cells, infiltrating the tissue in a persistent inflammatory pattern.5Journal of the American Academy of Dermatology. Acrodermatitis chronica atrophicans: A chronic T-cell-mediated immune reaction against Borrelia burgdorferi? The body keeps fighting but cannot clear the infection, and the ongoing inflammation gradually breaks down the skin’s normal structure.
How ACA Looks and Progresses
ACA typically develops in two overlapping stages. In the early inflammatory phase, the affected skin takes on a reddish or bluish-red discoloration, often with some swelling. The legs, especially the lower legs and feet, are the most common location, though it can appear on the hands and arms as well. At this point, the skin may feel warm and look faintly puffy, which is one reason it gets confused with circulatory problems.6PubMed Central. Acrodermatitis chronica atrophicans: various faces of the late form of Lyme borreliosis
Over months to years, the condition transitions into its atrophic phase. The skin becomes thin and wrinkled, often described as having a “cigarette paper” appearance. You can sometimes see the underlying blood vessels right through it. The normal structures within the skin, including hair follicles, sweat glands, and elastic tissue, are lost.7British Journal of Dermatology. P11 Acrodermatitis chronica atrophicans: a sign of late lyme disease Some patients also develop violaceous (purple-tinged) plaques or nodules, and fibrous nodules can appear near joints, reported in roughly 10 to 25 percent of cases.8The Open Dermatology Journal. Atrophosclerodermic Manifestations of Lyme Borreliosis – Section: Fibrotic Changes in ACA
Under the microscope, ACA tissue shows thinning of both the outer and deeper layers of skin, widened small blood vessels, and a characteristic band of inflammatory cells. Interstitial granulomatous patterns with thickened collagen bundles have also been observed, along with a reduction in certain skin fibroblasts similar to what is seen in morphea, a form of localized scleroderma.9PubMed. Histopathology and immunophenotype of acrodermatitis chronica atrophicans correlated with ospA and ospC genotypes of Borrelia species This overlap with scleroderma-like changes is not coincidental: localized fibrotic lesions and even morphea have been reported alongside ACA in some patients.10The Open Dermatology Journal. Atrophosclerodermic Manifestations of Lyme Borreliosis – Section: Fibrotic Changes in ACA
The Misdiagnosis Problem
ACA is frequently mistaken for something else, sometimes for years. The most common misdiagnosis is chronic venous insufficiency, the condition where veins in the legs have trouble returning blood to the heart, causing swelling, discoloration, and skin changes. The resemblance is not superficial. ACA on the lower leg can increase local blood flow, raise skin temperature, and dilate the small veins just beneath the surface, mimicking the hallmarks of venous disease so closely that even experienced clinicians are fooled.11PubMed. Acrodermatitis chronica atrophicans Herxheimer can often mimic a peripheral vascular disorder
One case report describes a 15-year-old girl whose ACA was misdiagnosed as venous insufficiency for six years before the correct diagnosis was made.12PubMed. Acrodermatitis chronica atrophicans in a 15-year-old girl misdiagnosed as venous insufficiency for 6 years This case also highlights that ACA is not exclusively a disease of older adults; while it overwhelmingly affects middle-aged and elderly people, it can appear in children and teenagers, further complicating the diagnostic picture.
The key differentiating feature is that ACA responds to blood tests for Borrelia, while venous insufficiency does not involve an infection at all. Clinicians working in endemic areas have stressed that ACA should be considered in any patient presenting with bluish-red skin changes on the lower extremities, with or without swelling and skin thinning.13PubMed Central. Differential diagnosis of acrodermatitis chronica atrophicans with emphasis on chronic venous insufficiency
Nerve Damage Alongside Skin Damage
ACA is not just a skin problem. A substantial proportion of patients develop peripheral neuropathy, meaning damage to the nerves in their limbs. In a study of 63 consecutive untreated ACA patients, about two-thirds showed clinical or measurable signs of nerve damage, compared to roughly a quarter of age-matched controls. The most common pattern was a symmetric sensory neuropathy affecting the extremities, with symptoms like pain and tingling reported far more often than in the control group.14PubMed. Peripheral neuropathy in acrodermatitis chronica atrophicans – a late Borrelia manifestation
Particularly telling was the observation that when the neuropathy was localized or asymmetric, the nerve changes were found more often in limbs that had visible ACA lesions than in unaffected limbs. This pattern suggests the nerve damage is not just a systemic complication of Lyme disease floating around the body, but something closely tied to the local presence of the infection in the skin and surrounding tissues. For patients, this means the numbness, tingling, or burning sensations they feel in an ACA-affected leg are probably directly related to the skin lesion, not a separate problem.
Joint and Bone Changes
In advanced cases, ACA can affect the musculoskeletal system beneath the damaged skin. Joint subluxation, where the bones in a joint partially slip out of alignment, has been documented in the hands and feet of ACA patients. Periosteal thickening, a change to the outer layer of bone, has been reported on X-rays of affected lower limbs.15PubMed. Joint and bone involvement in Dutch patients with Lyme borreliosis presenting with acrodermatitis chronica atrophicans These changes develop in long-standing untreated disease and reflect just how deep the damage can go when the infection persists for years. Once joint subluxation has occurred, antibiotic treatment can stop the infection but cannot reverse the structural deformity.
Getting the Diagnosis Right
The diagnosis of ACA rests on a combination of clinical appearance and blood testing. Serological testing for Borrelia antibodies is the cornerstone. Unlike early Lyme disease, where antibody levels may not yet be detectable, ACA produces reliably strong immune responses. In a large Slovenian cohort of 693 ACA patients, every single patient had detectable IgG antibodies against Borrelia, and the antibody levels were characteristically very high.16PubMed Central. Acrodermatitis chronica atrophicans: clinical and microbiological characteristics of a cohort of 693 Slovenian patients Earlier work using a specialized antibody test similarly found IgG antibodies in all ACA sera tested, indicating persistent immune recognition of the bacteria even years into the disease.17PubMed Central. Serodiagnosis of erythema migrans and acrodermatitis chronica atrophicans by the Borrelia burgdorferi flagellum enzyme-linked immunosorbent assay
This consistency is actually good news in a diagnostic sense: if you suspect ACA and the Borrelia IgG test is negative, you can be fairly confident the diagnosis is wrong. The false-negative rate for IgG serology in established ACA appears to be essentially zero. IgM antibodies, on the other hand, are less helpful. They were present in about a third of patients in the Slovenian cohort, but earlier research has shown that IgM reactivity in ACA sera may be nonspecific and related to rheumatoid factor rather than active early infection.18PubMed Central. Serodiagnosis of erythema migrans and acrodermatitis chronica atrophicans by the Borrelia burgdorferi flagellum enzyme-linked immunosorbent assay
Skin biopsy with laboratory testing is sometimes used as a supplementary tool, though the bacteria are notoriously difficult to grow from ACA tissue. In one study, Borrelia was successfully cultured from nearly 80 percent of erythema migrans (early Lyme rash) specimens but from none of the ACA lesions.19PubMed Central. Diagnostic value of PCR for detection of Borrelia burgdorferi in skin biopsy and urine samples from patients with skin borreliosis Molecular detection methods can pick up bacterial DNA in ACA biopsies, but with variable success rates depending on the technique used.20Clinical Microbiology and Infection. Detection of Borrelia afzelii, Borrelia burgdorferi sensu stricto, Borrelia garinii and group VS116 by PCR in skin biopsies of patients with erythema migrans and acrodermatitis chronica atrophicans In practice, blood serology combined with a compatible clinical picture is usually enough to make the diagnosis without a biopsy.
Treatment and Why Duration Matters
ACA responds to antibiotic therapy, but not all regimens are equally effective. The critical variable turns out to be how long you treat, not which drug you use. A study comparing intravenous ceftriaxone (given for 15 days) to oral antibiotics like doxycycline or penicillin V (given for 20 to 30 days) found that the choice of antibiotic mattered less than the length of the course. Among patients treated orally for only 20 days, more than half needed retreatment within six months because of persistent skin changes, neuropathy, or joint pain. Extending oral treatment to 30 days dramatically improved outcomes.21PubMed. Success and failure in the treatment of acrodermatitis chronica atrophicans
Even intravenous ceftriaxone, often considered the big-gun option for late Lyme disease, showed incomplete skin clearing in roughly a quarter of treated patients when given for only 15 days. Two out of five ceftriaxone patients who were monitored for bacterial DNA were still positive after a year. These findings reinforce that ACA is not a condition you can treat with a quick course and walk away from. Thirty days of oral antibiotics has become the accepted minimum, and follow-up over at least a year is standard practice to catch treatment failures early.
When treatment does work, the inflammatory redness and swelling tend to improve first. Skin atrophy that has already set in, however, does not fully reverse. If the skin has already thinned to the cigarette-paper stage, that structural loss is largely permanent. This is the strongest argument for early recognition: the sooner ACA is caught and treated, the less irreversible damage accumulates.
Why ACA Is Rare Outside Europe
If you live in North America and have never heard of ACA, that tracks with the epidemiology. The condition is overwhelmingly a European disease. The Borrelia subtype found in virtually all ACA lesions, corresponding to B. afzelii, is rarely found in the United States.22PubMed. Molecular subtyping of Borrelia burgdorferi in erythema migrans and acrodermatitis chronica atrophicans North American Lyme disease is caused almost entirely by Borrelia burgdorferi sensu stricto, a species that tends to produce joint inflammation (Lyme arthritis) and neurological disease rather than the chronic skin destruction seen in ACA. The geographic distribution of Borrelia species essentially dictates which late complications of Lyme disease you are most likely to encounter.
This geographic divide also means that physicians in the United States rarely see ACA in their careers, which contributes to diagnostic delay when cases do appear. Occasional cases have been reported in North American patients, sometimes in people with a history of European travel. Clinicians in regions where Lyme disease is common but ACA is not should keep the condition somewhere in their mental filing cabinet, particularly when evaluating patients who have spent time in European tick-endemic areas and present with unexplained bluish-red skin changes on the extremities.
Co-infections and Complications
As with other forms of Lyme disease, ACA can occasionally co-occur with other tick-borne infections. Cases involving apparent co-infection with Bartonella species have been reported alongside complex ACA presentations.23PubMed Central. Presentation of Acrodermatitis Chronica Atrophicans Rashes on Lyme Disease Patients in Canada Co-infections can complicate both the clinical picture and the treatment response, making an already tricky diagnosis even harder to sort out.
Beyond the skin, nerves, and joints already discussed, ACA has also been reported alongside localized scleroderma-like conditions such as morphea and lichen sclerosus. Whether these represent direct effects of the Borrelia infection or coincidental autoimmune phenomena triggered by the chronic inflammatory state is still debated. The overlap is clinically relevant because it means a patient with ACA may develop hardened, fibrotic skin patches that look nothing like the typical ACA lesion, potentially sending the diagnostic workup in the wrong direction.
A Disease Named Over a Century Ago
ACA is not a newly recognized condition. The term was coined by Herxheimer and Hartmann in 1902 to describe a form of progressive skin atrophy.24JAMA Dermatology. Acrodermatitis Chronica Atrophicans For decades, the cause was unknown. It was only with the identification of Borrelia burgdorferi as the agent of Lyme disease in the early 1980s, and subsequent European research identifying B. afzelii as a distinct species in the 1990s, that ACA was definitively placed within the spectrum of Lyme borreliosis. The Herxheimer of ACA fame, incidentally, is the same family name associated with the Jarisch-Herxheimer reaction, the temporary worsening of symptoms sometimes seen when spirochetal infections are treated with antibiotics. Adolf Jarisch and Karl Herxheimer described that phenomenon independently around the same time, working with syphilis patients. The Herxheimer who named ACA was Karl’s brother, Fritz. The family’s involvement in both conditions is a small historical coincidence that reflects how deeply spirochetal infections shaped early twentieth-century dermatology.