Erythema migrans A69.2

First and most frequent localized early manifestation of the skin in the vicinity of the tick bite site with circular (disc-shaped) or oval, slowly centrifugally growing erythema, belonging to Lyme borreliosis. The infection is caused by Borrelia burgdorferi. Typically, erythema migrans appears 10-30 days after infection. Erythema migrans can be very discrete, so that it is not noticed or is noticed very late (only about half of patients with late manifestations of Lyme disease remember an early clinical presentation!). Multiple erythemata migrantia occur in 5-10% of cases (in children > than in adults). Note: By definition, erythema migrans is called erythema chronicum migrans if it persists for more than 6 months.

Borrelia burgdorferi

The age of the initial manifestation depends on the time of infection. In this respect, there are no disease-specific first manifestations.

Usually: 5-15 years, 40-80 years.

There is no sex predilection.

Buttocks, trunk, extremities. In children: Not rarely head and neck area.

After an incubation period of 10-30 days following a tick bite, 60-90% of infected persons develop a roundish-oval, sharply edged, centrally pale, pale red or livid red erythema, which slowly expands centrifugally, starting from a central, reddened spot or a reddish papule. If the erythema persists for a longer period of time, a ring-like structure develops due to central fading, which often shows a central stitch reaction in the form of a red papule. The clinical variability is great, so that urticarial or highly red or stationary erythema or plaques may also appear.

Vesicular forms are rarely observed.

Spontaneous healing usually occurs after an average of 10 weeks, longer persistence and local recurrences are possible. May be accompanied by swelling of the lymph nodes, arthralgia, headaches and flu-like impairment of the general condition.

Erythema chronicum migrans may be associated with lymphadenosis cutis benigna (lymphocytoma), especially if the earlobes, nipples and scrotal region are involved.

In childhood, erythema chronicum migrans shows some clinical peculiarities: e.g. manifestations mainly in the head and neck area. Uncharacteristic, transient erythema may occur on the face.

Multilocular erythema migrans: Multiple occurrence of erythema migrans was observed in 10% of cases in a large Italian study and is considered a sign of disseminated early infection of Lyme borreliosis.

Typical erythema migrans:

• Bite site visible in the center
• Findings accentuated at the edges, not raised
• Diameter of the erythema >5 cm

Atypical erythema migrans:

• Homogeneous, non-edge accentuated findings
• No tendency to spread
• Tick bite site not visible
• Central red papule not visible
• Raised border
• Inhomogeneous blotchy findings
• Central vesicular erythema
• Hemorrhagic erythema

A serological examination and, if necessary, direct detection of the pathogen should only be carried out if there is reasonable clinical suspicion.

Antibodies can be detected in 50% of patients in the first 2 weeks after infection and in 80% of patients after > 4 weeks. The guidelines of the microbiological quality standards (MiQ = acronym for "quality standards in microbiological-infectiological diagnostics") recommend the detection of separate IgG and IgM antibodies using a sensitive ELISA and, if positive, an analysis using a specific immunoblot.

Some possible pitfalls and misinterpretations should be taken into account. For example, a lack of IgM antibodies does not rule out an acute infection. On the other hand, IgM antibodies can also persist for months to years after Lyme disease has been treated. A serological check after treatment does not provide any information about the success of the treatment, so serological follow-up checks are not useful. If the initial diagnosis is carried out at an early stage when the parameters are still negative, but Lyme borreliosis is still suspected due to the typical clinical symptoms, it makes sense to repeat the serology after three to four weeks.

Caution: The detection of IgM antibodies without typical clinical symptoms is not an indication for treatment.

• Insect bite reaction: Hyperergic insect bite reactions (see below Insect bite) are observed a few hours after the bite event. A "free interval" as for the early form of cutaneous Lyme disease does not exist.
• Tinea corporis: Characteristic are scaly red plaques at the edges, usually associated with itching. Rarely solitary. Mycological (native and cultural) evidence possible in untreated foci.
• Erysipelas: onset with an asymmetric, usually originating from a small lesion, flaming red, painful, sharply demarcated erythema or plaque. Fever and chills may precede or accompany the process.
• Drug reaction, fixed: "Suddenly present" solitary or confined to a few foci, 2.0-5.0 cm in size (rarely larger), round or oval, highly inflammatory, initially rich red, later blue- to brown-red, after healing brown (postinflammatory hyperpigmentation), sharply demarcated, succulent, pruritic, or even slightly painful patches or plaques. Acuity of the event speaks against erythema chronicum migrans, which is chronically insidious.
• Erythema anulare centrifugum: Rarely solitary, usually multiple, anular, sometimes polycyclic, slowly centrifugally growing plaques, typically smooth on the surface, with little or no pruritus. Almost pathognomonic is the palpatory finding: when stroking from the center to the periphery of a foci, the marginal mound feels like a "wet woolen thread under the skin". Histology is often characteristic.
• For multiple erythema chronica migrantia see below. Lyme disease.
• Erythema infectiosum: In cases of facial involvement and multiple lesions, parvo B-19 infection (serology, acuity of manifestations, fever) should be excluded.
• Erysipeloid: Bacterial zoonosis limited exclusively to contact persons (fishermen, butchers, housewives). Occurs mainly on the hands. Minor clinical symptoms.

S.u. Lyme borreliosis.

Favourable; completely curable with sufficient antibiotic therapy.

In a follow-up period of more than 15 years (Weitzner 2015) with sufficiently treated erythema migrans, a so-called PTLDS (post-treatment Lyme disease symptom) could be diagnosed in about 5% of the cases. This manifests itself in unspecific symptoms such as joint and muscle pain, fatigue and concentration disorders. The entity of PDLDS is controversial.

Erythema migrans is accompanied by flu-like general symptoms in about 30% of infected persons, especially in children.

The detection of specific antibodies can occur very delayed (more than 12-16 weeks after the stinging event), so that in case of negative serology the diagnosis should be made clinically.

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