Acrodermatitis chronica atrophicans (ACA) is the third or late stage of European Lyme borreliosis. [1, 2] This unusual progressive fibrosing skin process is caused by an ongoing active infection with Borrelia afzelii. First delineated in 1883,  it was described in 1902 as a tissue paper–like cutaneous atrophy.  See the image below.
See Lyme Disease and 4 Emerging Tick-Borne Illnesses, a Critical Images slideshow, to help identify and treat several tick-borne conditions.
ACA is evident on the extremities, particularly on the extensor surfaces. It begins with an inflammatory stage characterized by bluish red discoloration and cutaneous swelling and concludes several months or years later with an atrophic phase. Sclerotic skin plaques may also develop. Physicians should use serologic and histologic examination to confirm this diagnosis.
The choice of treatment for ACA depends on the coexistence of other signs or symptoms of Lyme borreliosis. Appropriate consultations (ie, a neurologist, ophthalmologist, rheumatologist, or cardiologist) should be sought if extracutaneous signs and symptoms are present. ACA patients without concurrent extracutaneous disease do not require hospitalization.
Pathophysiology and Etiology
B afzelii is the predominant etiologic agent of ACA but may not be the sole cause. Borrelia garinii, another genospecies of the Borrelia burgdorferi sensu lato (“in the broad sense”) complex, has also been detected in this setting.
ACA is the only form of Lyme borreliosis in which no spontaneous remission occurs. Its pathophysiology is not yet fully understood. ACA appears to be associated with long-term persistence of Borrelia organisms in the skin; several nonspecific reactions, together with a specific immune response, may contribute to its manifestations.
The persistence of the spirochetes despite a marked cutaneous T-cell infiltration and high serum antibody titers may be connected with the following factors:
Resistance of the pathogen to the complement system
The pathogen’s ability to escape to immunologically protected sites (eg, endothelial cells, fibroblasts)
The pathogen’s ability to change antigens, which may lead to an inappropriate immune response
Lack of protective antibodies, with a narrow antibody spectrum and a weak cellular response characterized by downregulation of major histocompatibility system (MHC) class II molecules on Langerhans cells, has been observed in patients with Lyme borreliosis.
A restricted pattern of cytokine expression in ACA, including lack of interferon gamma, may contribute to its chronicity. Cross-reactive antibody responses could take part in autoimmune damage, but whether autoimmune reactions play any role in the pathogenesis of the disease is unclear. The pathogenic mechanism of atrophic skin changes also has not been clarified. Perhaps periarticular regions are favored sites because of reduced acral skin temperatures or reduced oxygen pressure.
Lack of adequate or appropriate treatment of early Lyme borreliosis facilitates the development of ACA.
The occurrence of ACA is connected with the ecology of Lyme borreliosis, which varies in different geographical regions of the world.
United States statistics
Ixodes scapularis, Ixodes pacificus, and 4 other tick species distributed in North America transmit B burgdorferi sensu stricto (“in the strict sense”), causing erythema migrans and Lyme borreliosis arthritis.
Despite a high incidence of Lyme borreliosis in the United States (ranging from 95 cases per 100,000 population in Connecticut to 1250 cases per 100,000 population in Nantucket County, MA [1996 data]), ACA is not seen in the United States, except in a few European immigrants. 
The tick vectors of B afzelii, the main etiologic agent of ACA (and erythema migrans), are Ixodes ricinus, Ixodes hexagonus, and Ixodes persulcatus, which are distributed in western and central Europe and in far eastern Europe and Asia. Almost all of these hard tick species may also transmit B garinii, a causative agent of erythema migrans and neurologic symptoms of Lyme borreliosis.
In Europe, Lyme borreliosis with all its dermatologic manifestations occurs in almost all countries, predominantly in the central part of the continent. The annual incidence ranges from 16 cases per 100,000 population in France to 120 cases per 100,000 population in northeastern Poland and Slovenia and to 130 cases per 100,000 population in Austria (1995 data). 
The overall prevalence of ACA in all European patients with Lyme borreliosis is about 1-10%, depending on the region of the population sampled. Among the group of patients with skin manifestations of Lyme borreliosis observed in Vienna, the ratio of erythema migrans cases to ACA cases and to Borrelia lymphocytoma (BL) cases was 30:3:1. In the authors’ as-yet-unpublished studies (involving a group of patients with Lyme borreliosis in northeastern Poland), this ratio is 170:5:1.
Because the clinical diagnosis of ACA is much more difficult than that of erythema migrans or BL, the condition is often underdiagnosed; in fact, the ratio of erythema migrans cases to ACA cases may be higher than those already cited. The total number of cases could increase with the frequency of untreated European Lyme borreliosis rises. ACA is probably the most common late and chronic manifestation of the borreliosis seen in European patients with Lyme disease.
A Bulgarian survey found that both BL and ACA were rare (0.3%). 
Of over 700 patients from an endemic region of northern Italy, erythema migrans was noted in more than half, with 7 having lymphadenosis benigna cutis and 18 ACA. 
ACA can occur in any age group but it is most common in adults, mainly those in their 40s or 50s. The youngest of the authors’ patients was 26 years of age; the oldest was 73 years.  The mean age of the female group was 54.3 ± 12.8 years; the mean age of the male group was 46.2 ± 6.5 years. ACA is rare in adolescents; however, it has been observed in children. A case in a 15-year-old girl was reported by Zalaudek et al in 2005. 
More than two thirds of patients with ACA are women. Of the authors’ 19 patients, only 5 were men. 
ACA is not limited to any nationality or race. In general, however, it is much more frequent in whites than in persons of other races, probably because of a far higher exposure to ticks transmitting B afzelii.
The course of ACA is prolonged and may extend for as long as several years. It leads to extensive flaccid atrophy of the skin and, in some patients, to limitation of upper and lower limb joint mobility. Chronic, difficult-to-treat ulcerations of atrophic skin may develop after minor trauma. Bacterial superinfections may be seen.
The general status of patients with ACA remains good, though they may experience neurologic or rheumatologic signs and symptoms. As a rule, the outcome of treatment is good if the acute inflammatory stage of ACA is treated adequately. The therapeutic outcome is difficult to assess in patients with the chronic atrophic phase, in which many changes are only partially reversible.
Although ACA rarely occurs in childhood, its prognosis in pediatric patients is uncertain. For this reason, it should be treated as early as possible to prevent irreversible cutaneous damage. 
Rarely, a B-cell lymphoma may develop in these patients, as may a basal cell carcinoma or squamous cell carcinoma.  A metastatic cutaneous squamous cell carcinoma was described in a patient with long-standing ACA. On the whole, however, malignant degeneration has been quite uncommon; accordingly, ACA should not be considered a precancerous disorder.
Patients and their families should receive information about how to lower the risk of acquiring ACA. Persons residing in endemic areas should examine their bodies for ticks every 12 hours and should expeditiously remove any attached ticks. To discourage ticks from accessing exposed skin, they should use personal protection (eg, light-colored clothing to facilitate tick visualization) and tuck their pants cuffs into socks.
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