How can a tick bite be recognized without the tick present?

The Elusive Tick Bite: A Diagnostic Challenge

Understanding Tick-Borne Illnesses

Common Tick-Borne Diseases

When a tick detaches, the bite often leaves clinical clues that point to a recent exposure. Early manifestations of tick‑borne infections can serve as indirect evidence of an unnoticed attachment.

Lyme disease – erythema migrans: expanding, annular rash with central clearing, typically appearing 3–30 days after the bite; may be accompanied by flu‑like symptoms.
Rocky Mountain spotted fever – fever, headache, and a maculopapular rash that starts on wrists and ankles before spreading centrally; petechiae may develop.
Anaplasmosis – sudden onset of fever, chills, muscle aches, and mild leukopenia; occasional rash on the trunk.
Babesiosis – hemolytic anemia presenting with fatigue, jaundice, and dark urine; laboratory findings include intra‑erythrocytic parasites on blood smear.
Ehrlichiosis – fever, rash, and elevated liver enzymes; leukopenia and thrombocytopenia are common laboratory signs.
Tularemia – ulceroglandular form shows a painful papule at the bite site and regional lymphadenopathy; may progress to systemic illness.

Identifying these patterns prompts immediate medical assessment, laboratory testing, and, when indicated, antimicrobial therapy. Early detection mitigates complications and reduces the risk of long‑term sequelae.

Symptoms of Early Stage Infections

Early-stage tick‑borne infections often manifest before the arthropod can be seen. Recognizing these signs enables prompt treatment and reduces the risk of complications.

Fever, typically low‑grade (37.5–38.5 °C), may appear within days of exposure. Accompanying chills or sweats suggest systemic involvement.

Localized skin reactions provide the most direct clue. A red macule or papule at the bite site, sometimes expanding to a larger erythema, signals an inflammatory response. When the lesion develops a central clearing surrounded by a reddish halo, it is characteristic of certain Borrelia infections.

Flu‑like symptoms frequently accompany the rash. Headache, muscle aches, and joint stiffness often emerge concurrently. In some cases, mild nausea or a transient lymphadenopathy near the bite area occurs.

Neurological signs, although less common in the first week, can include tingling or numbness in the extremities. Early ocular irritation, such as mild conjunctival redness, may also be reported.

A concise checklist for clinicians and patients:

Temperature ≥ 37.5 °C without another obvious source
Erythematous lesion, especially with central clearing
Headache, myalgia, or arthralgia
Regional lymph node enlargement
Paresthesia or mild visual discomfort

Presence of two or more items warrants diagnostic testing for tick‑borne pathogens, even when the tick itself cannot be retrieved. Prompt antimicrobial therapy based on identified agents improves outcomes and prevents progression to disseminated disease.

Incubation Periods for Various Pathogens

Tick exposure often becomes apparent only after the arthropod has detached, making knowledge of pathogen incubation essential for early detection. Each tick‑borne microorganism follows a characteristic latency between inoculation and symptom onset; recognizing these intervals helps clinicians infer a recent bite when the vector is no longer visible.

Borrelia burgdorferi (Lyme disease): 3–30 days; erythema migrans appears as a expanding annular rash, sometimes accompanied by fever, headache, or fatigue.
Anaplasma phagocytophilum (Anaplasmosis): 5–14 days; abrupt fever, chills, myalgia, and leukopenia develop, often without a rash.
Babesia microti (Babesiosis): 1–4 weeks; hemolytic anemia, jaundice, and intermittent fever emerge, typically after a flu‑like prodrome.
Rickettsia rickettsii (Rocky Mountain spotted fever): 2–14 days; high fever, severe headache, and a maculopapular rash that begins on wrists and ankles before spreading centrally.
Francisella tularensis (Tularemia): 3–5 days; ulceroglandular form presents with a painful skin ulcer at the bite site and regional lymphadenopathy.
Powassan virus: 1–5 days; encephalitic symptoms such as confusion, seizures, or focal neurologic deficits may arise rapidly.

When a patient reports recent outdoor activity in tick‑infested areas and exhibits signs that align with these incubation windows, the likelihood of a prior tick attachment increases. Absence of a visible engorged tick does not preclude infection; the temporal pattern of symptom emergence provides a reliable proxy for the missed exposure. Prompt laboratory testing and empiric therapy should be guided by the specific incubation profile matched to the clinical presentation.

Recognizing Clues in the Absence of the Tick

Examining the Bite Site

Redness and Swelling Patterns

Redness and swelling around a bite site often provide the first clue that a tick has fed and detached. The reaction usually appears as a localized, circular erythema that may expand over hours to days. When the lesion is symmetric and well‑defined, it suggests the attachment point of the arthropod.

Typical patterns include:

A uniform, round halo of redness measuring 2–5 cm in diameter, often referred to as a “target” or “bull’s‑eye” appearance.
A central area of pallor surrounded by a reddish ring, indicating localized vasodilation with peripheral inflammation.
Progressive enlargement of the erythema, exceeding 5 cm, which may signal delayed hypersensitivity or infection.
Accompanying edema that follows the same contour as the redness, producing a raised, firm border.

The timing of these signs is also diagnostic. Immediate swelling and mild redness can appear within minutes of attachment, while a more pronounced, expanding rash typically develops 24–72 hours after the tick is gone. Persistent or worsening lesions beyond a week warrant medical evaluation for possible Lyme disease or other tick‑borne illnesses.

Rashes Associated with Tick Bites

Rash development is the most reliable external indicator of a recent tick attachment when the arthropod is no longer visible.

Erythema migrans: expanding, oval or circular redness with central clearing; diameter often exceeds 5 cm; appears 3–30 days after bite; may be warm but usually painless.
Local erythema: small, uniform redness at the bite site; may be accompanied by swelling, itching, or mild pain; develops within hours to a few days.
Papular or vesicular lesions: raised, firm bumps or fluid‑filled blisters; can occur on the extremities or trunk; may precede or accompany systemic symptoms.

Distinguishing features include lesion size, shape, progression, and timing. Erythema migrans expands gradually and remains relatively uniform in color, whereas inflammatory reactions to other insect bites often produce irregular, rapidly changing patterns and are frequently pruritic. Presence of a target‑shaped or “bull’s‑eye” appearance strongly suggests a tick‑borne pathogen.

When any of these rashes are identified, especially in regions where ticks are endemic, immediate medical evaluation is warranted. Early antimicrobial therapy reduces the risk of severe complications such as Lyme disease, anaplasmosis, or Rocky Mountain spotted fever. Documentation of rash characteristics, onset date, and recent outdoor exposure assists clinicians in selecting appropriate diagnostic tests and treatment protocols.

Itching and Pain Characteristics

A bite that has already detached leaves a distinct pattern on the skin. The lesion often appears as a small, red papule surrounded by a wider area of erythema. Absence of the arthropod does not obscure the clinical picture; careful observation of the cutaneous response provides the primary clue.

Itching characteristics

Persistent or intermittent pruritus developing within hours to days after exposure.
Intensification during warm weather or after sweating.
Localized to the bite site, rarely spreading to distant areas.
May be accompanied by a faint, raised border that delineates the bite margin.

Pain characteristics

Sharp, stabbing sensation at the moment of attachment, often remembered even after the tick is gone.
Dull throbbing pain that persists for several days, usually confined to the immediate vicinity of the lesion.
Sensitivity to pressure or light touch over the bite area.
Absence of widespread muscular or joint pain, which helps differentiate from other arthropod reactions.

When the tick is no longer visible, the combination of a localized erythematous papule, focused itching, and confined pain constitutes a reliable indicator of a recent bite. Early identification allows prompt removal of any residual mouthparts and initiation of appropriate prophylactic measures.

Systemic Symptoms Indicative of Infection

Fever and Chills

Fever and chills often emerge as early systemic responses when a tick bite has occurred but the tick is no longer attached. The body’s immune reaction to tick saliva proteins can trigger a rapid rise in temperature, typically accompanied by rigors that appear without an obvious source of infection.

Sudden onset of fever within 24–72 hours after outdoor exposure
Intermittent chills, sometimes alternating with periods of normal temperature
Absence of respiratory or gastrointestinal symptoms that would suggest alternative causes
Accompanying localized skin changes such as a faint erythema, a central punctum, or a rash that develops days after the bite

When these signs appear after a recent hike, camping trip, or time spent in tick‑infested areas, clinicians should consider a recent tick exposure even if the arthropod cannot be found. Laboratory evaluation may reveal leukocytosis or elevated inflammatory markers, supporting an infectious process linked to tick‑borne pathogens.

Prompt recognition of fever and chills as potential evidence of a missed tick bite enables early diagnostic testing for diseases such as Lyme disease, Rocky Mountain spotted fever, or anaplasmosis, and facilitates timely antimicrobial therapy.

Fatigue and Malaise

Fatigue and malaise frequently appear after an unnoticed tick attachment and can serve as indirect evidence of a bite. These systemic symptoms often develop within days to weeks of the tick’s feeding period, reflecting the host’s immune response to tick saliva proteins or early infection with tick‑borne pathogens.

Key points for clinical assessment:

Persistent tiredness not attributable to lifestyle changes or other illnesses.
Generalized feeling of weakness or heaviness, often accompanied by low‑grade fever.
Absence of localized skin changes does not exclude a bite; systemic signs may precede rash.
Onset of symptoms after outdoor exposure, especially in wooded or grassy areas, increases suspicion.
Laboratory findings such as mild leukopenia or elevated inflammatory markers can support the diagnosis when correlated with exposure history.

When fatigue and malaise are present alongside a recent history of possible tick exposure, clinicians should consider a tick bite in differential diagnosis and pursue appropriate serologic or molecular testing for vector‑borne diseases. Early identification enables timely treatment and reduces the risk of complications.

Muscle and Joint Aches

Muscle and joint aches often appear early after a tick bite, even when the arthropod has already detached. The pain typically manifests as diffuse soreness rather than localized tenderness, distinguishing it from ordinary strain injuries. In many cases, the discomfort emerges within 24–48 hours and may persist for several days.

Key characteristics of tick‑related musculoskeletal pain include:

Symmetrical involvement of multiple joints, especially knees, elbows, and wrists.
Absence of swelling or overt inflammation in the affected areas.
Co‑occurrence with other systemic signs such as fever, headache, or a rash that may develop later.

When these symptoms arise after outdoor exposure in tick‑infested regions, clinicians should consider a recent bite as a probable source. Laboratory testing for tick‑borne pathogens (e.g., Borrelia burgdorferi) can confirm infection, but the presence of muscular and joint discomfort alone provides a practical clue for early detection. Prompt recognition enables timely antimicrobial therapy, reducing the risk of chronic complications.

Headaches and Neck Stiffness

Headaches and neck stiffness may be the first clues that a recent tick attachment has occurred, even when the arthropod is no longer visible. The onset of a dull, persistent headache within days to weeks after outdoor exposure suggests early systemic involvement. Neck stiffness, especially when accompanied by mild photophobia, indicates meningeal irritation, a hallmark of early Lyme neuroborreliosis.

Key clinical points:

Headache appears without a clear alternative cause, often described as pressure‑type rather than migraine‑like.
Neck rigidity manifests as reduced range of motion or pain on flexion, sometimes with a sensation of tightness rather than true spasm.
Accompanying signs may include low‑grade fever, fatigue, or a recent erythematous rash that has resolved.
Laboratory testing for Borrelia antibodies can confirm infection, but results may be negative in the first two weeks; empirical treatment is justified when clinical suspicion is high.

When these symptoms emerge after a recent hike, camping trip, or work in wooded areas, clinicians should consider a concealed tick bite as a possible source. Prompt evaluation, including a lumbar puncture if meningitis is suspected, and early antibiotic therapy reduce the risk of long‑term neurological complications.

Differentiating from Other Insect Bites and Skin Conditions

Mosquito Bites vs. Tick Bites

Mosquito bites appear within minutes of exposure, presenting as small, raised papules surrounded by a faint red halo. The central puncture is often invisible, and the lesion may itch intensely for a few hours to a day. Typical locations include exposed skin such as arms, legs, and face. The reaction is usually uniform, with no central necrosis or ulceration.

Tick bites develop more slowly. After attachment, a painless nodule forms at the attachment site, often surrounded by a clear area of skin that may be slightly raised. The nodule can persist for several days, sometimes weeks, even after the tick detaches. Common attachment sites are warm, protected areas—behind the knees, in the groin, under the armpits, and on the scalp. Unlike mosquito lesions, tick bites may exhibit a central puncture wound that is difficult to see, and the surrounding skin can become erythematous or develop a rash.

Key distinguishing features:

Onset: mosquito reaction appears immediately; tick reaction emerges after several hours to days.
Size and shape: mosquito papule is typically 2–5 mm, round, with a diffuse halo; tick nodule may be larger, irregular, and may show a central dark spot where the mouthparts were embedded.
Location: mosquito bites favor exposed areas; tick bites favor concealed, hair‑covered regions.
Duration: mosquito lesion resolves within 24–48 hours; tick nodule can linger for weeks, sometimes accompanied by a spreading rash.
Systemic signs: tick bites may be followed by fever, fatigue, or a bullseye‑shaped erythema (erythema migrans), which are absent in mosquito reactions.

When the arthropod is not present, clinical assessment should focus on the lesion’s chronology, anatomical site, and evolution. Persistent, localized nodules in hidden skin regions, especially when accompanied by a spreading erythema, strongly suggest a tick attachment even if the tick itself cannot be visualized. Conversely, rapid‑onset, intensely itchy papules on exposed skin indicate mosquito exposure.

Spider Bites vs. Tick Bites

Spider and tick bites often appear similar at first glance, yet they present distinct clinical patterns that allow identification even when the culprit is absent.

A tick attachment typically produces a painless, rounded erythema measuring 2–5 mm. A central punctum or “tick mouth” may be visible, sometimes surrounded by a faint halo. Within days to weeks, the lesion can expand into a larger, annular rash (erythema migrans) especially with Borrelia infection. Bites are frequently located on lower limbs, scalp, or areas concealed by clothing. Systemic signs, such as fever, fatigue, or headache, often develop later and correlate with pathogen transmission rather than the bite itself.

Spider envenomation usually causes immediate, sharp pain followed by localized swelling. Necrotic species (e.g., brown recluse) generate a violaceous blister that evolves into a deep ulcer with surrounding tissue death. Other spiders produce erythematous wheals that resolve within hours. Bites often occur on exposed skin—hands, arms, or face—and may be accompanied by systemic symptoms like nausea, muscle cramps, or, rarely, hemolysis.

Recognizing a tick bite without the arthropod relies on several observations:

Absence of intense initial pain; the bite feels mild or unnoticed.
Presence of a small, smooth papule with a central punctum.
Development of a slowly expanding, symmetric erythema, sometimes with central clearing.
Recent exposure to tick‑infested habitats (wooded areas, tall grass, pet grooming).

Distinguishing features summarized:

Pain onset: spider – immediate, severe; tick – minimal or delayed.
Lesion size: spider – variable, may become necrotic; tick – 2–5 mm initially, may enlarge slowly.
Central mark: tick – visible punctum; spider – often absent.
Location: spider – exposed skin; tick – concealed or hair‑covered areas.
Systemic timeline: spider – rapid onset; tick – delayed, linked to pathogen incubation.

By evaluating these criteria, clinicians can infer a tick bite even when the insect is no longer attached, and differentiate it from spider envenomation.

Allergic Reactions and Rashes

Allergic reactions and skin rashes provide the most reliable clues when a tick bite must be identified after the arthropod has detached. The immune response to tick saliva often manifests within hours to days, producing distinct patterns that differ from common irritant dermatitis.

Typical manifestations include:

A red, expanding annular lesion (often called a “bull’s‑eye” or target rash) centered on the bite site.
Localized swelling or edema surrounding the erythema, sometimes accompanied by a warm sensation.
Pruritus that intensifies over 24–48 hours, indicating histamine release.
Small vesicles or papules that may coalesce into a larger plaque.
Systemic signs such as urticaria, angio‑edema, or shortness of breath, suggesting a generalized allergic response.

Differential considerations:

Contact dermatitis – usually confined to the area of direct contact with an irritant; lacks the concentric rings typical of tick‑related lesions.
Spider or insect bites – often present as punctate wounds with surrounding necrosis; the rash is not typically target‑shaped.
Early Lyme disease – may begin as a subtle erythema without pronounced swelling; the classic target pattern evolves over several days.

Clinical assessment should focus on the lesion’s morphology, progression, and any accompanying systemic symptoms. Prompt recognition enables early intervention, such as antihistamines for allergic inflammation or antibiotics if Lyme disease is suspected.

When to Seek Medical Attention

Warning Signs Requiring Immediate Medical Care

Spreading Rashes

A spreading rash can be the first clue that a tick attachment has occurred even after the insect has detached. The most common pattern is a concentric, expanding erythema that often begins as a small red spot at the bite site and enlarges over hours to days. Typical features include:

Clear central area with a surrounding ring of redness, sometimes described as a “bull’s-eye” appearance.
Diameter increasing by several millimeters each day, reaching up to 5 cm or more.
Uniform color without vesicles or pustules in early stages.

Accompanying signs may reinforce suspicion:

Localized itching or mild pain at the expanding edge.
Low‑grade fever, fatigue, or headache developing within a week.
Absence of a visible tick or attached mouthparts.

Differential considerations such as allergic reactions, fungal infections, or cellulitis can be excluded by noting the rapid, symmetric expansion and the lack of purulent discharge. Laboratory testing is not required for initial assessment; visual inspection and measurement of the lesion’s growth rate provide sufficient information.

When the rash expands rapidly, exceeds 5 cm, or is accompanied by systemic symptoms, prompt medical evaluation is advised to rule out vector‑borne diseases and to initiate appropriate therapy.

Neurological Symptoms

Neurological manifestations can signal a recent tick exposure even when the insect is no longer attached. Early infection with tick‑borne pathogens such as Borrelia burgdorferi (Lyme disease) or Anaplasma phagocytophilum often produces symptoms that precede visible skin changes.

Typical neurologic signs include:

Sudden facial weakness or drooping (often unilateral) indicating facial nerve palsy.
Sharp, stabbing headaches that intensify at night or with movement.
Neck stiffness or pain without a clear musculoskeletal cause.
Tingling, numbness, or burning sensations in limbs, frequently described as “pins‑and‑needles.”
Transient episodes of confusion, difficulty concentrating, or memory lapses.
Muscle weakness or loss of coordination, especially in the extremities.

When any of these symptoms appear after outdoor activities in tick‑infested areas, clinicians should consider a tick‑borne etiology and pursue appropriate laboratory testing and treatment. Prompt identification reduces the risk of chronic neurologic damage.

Cardiac Abnormalities

Tick‑borne infections may manifest after the arthropod has detached, and cardiac involvement often provides the first clinical clue. Pathogens such as Borrelia burgdorferi and Rickettsia species can provoke inflammation of the myocardium, conduction system disturbances, and pericardial effusion. When a patient reports recent outdoor exposure but no attached tick, clinicians should evaluate cardiac function for indirect evidence of a bite.

Typical cardiac abnormalities associated with recent tick exposure include:

Atrioventricular block of any degree, frequently reversible with antimicrobial therapy.
Myocarditis presenting as chest discomfort, dyspnea, or elevated cardiac enzymes.
Pericardial effusion detectable by echocardiography, often asymptomatic in early stages.
Tachyarrhythmias, especially supraventricular premature beats, that arise without prior cardiac history.

Electrocardiographic monitoring, serum biomarkers (troponin, C‑reactive protein), and imaging studies form the core diagnostic approach. Absence of a visible tick does not exclude infection; cardiac signs may prompt serologic testing and early treatment, reducing the risk of long‑term sequelae.

Severe Joint Pain

Severe joint pain may signal a recent tick exposure even when the tick itself is no longer visible. The pain often appears abruptly, can be intense, and may involve a single joint or migrate between several joints. Pathogens transmitted by ticks—most notably Borrelia burgdorferi, the agent of Lyme disease—trigger inflammatory arthritis that manifests as sharp, aching discomfort, joint swelling, and limited range of motion.

Clinical clues that suggest a tick bite despite the absence of the arthropod include:

Sudden onset of severe arthralgia without prior injury
Pain that shifts from one joint to another over days or weeks
Accompanying low‑grade fever or chills
Flu‑like fatigue or headache
History of recent outdoor activity in endemic regions (forests, grasslands, high‑humidity areas)

When these signs are present, the diagnostic work‑up should focus on exposure risk and laboratory confirmation. A thorough patient history should document recent hikes, camping trips, or gardening in known tick habitats. Serologic testing for Lyme disease (ELISA followed by Western blot) and, when appropriate, polymerase chain reaction assays for other tick‑borne agents (e.g., Anaplasma, Ehrlichia) provide objective evidence. Imaging of affected joints can reveal effusion or synovial thickening, supporting an inflammatory process.

Prompt treatment reduces the likelihood of chronic joint damage. Empiric doxycycline or amoxicillin, initiated within weeks of symptom onset, is standard for early Lyme arthritis. Persistent or recurrent pain warrants referral to a rheumatologist for further evaluation and possible adjunctive anti‑inflammatory therapy. Regular follow‑up assesses symptom resolution and monitors for late‑stage complications such as persistent arthropathy.

Information to Provide to Your Doctor

Recent Outdoor Activities

Recent hiking, camping, and trail running have increased skin exposure to environments where ticks reside. Absence of the attached parasite does not eliminate the need for early detection because the bite often leaves recognizable signs.

Typical local manifestations appear within hours to days after exposure:

Small, painless red spot at the bite site, sometimes resembling a mosquito bite.
A concentric ring‑shaped rash (often called a “bull’s‑eye”) developing 3–7 days post‑bite.
Swelling or itching around the initial puncture.

Systemic indicators may follow the cutaneous signs:

Fever, chills, or fatigue.
Muscle aches, joint pain, or headache.
Nausea or gastrointestinal upset.

When these symptoms arise after recent outdoor activity, a thorough self‑inspection is warranted. Examine the entire body, focusing on hidden areas such as scalp, armpits, groin, and behind knees. If any of the described lesions are present, seek medical evaluation promptly to rule out tick‑borne infections and initiate appropriate treatment.

Travel History

Travel history provides essential context for diagnosing a bite that may have originated from a tick, even when the arthropod is no longer attached. Recent or past journeys to regions where ticks are endemic raise the pre‑test probability of tick exposure and guide clinicians toward specific investigations.

Key aspects of travel history that aid recognition include:

Destination(s) known for tick‑borne pathogens such as Borrelia burgdorferi (eastern United States, Europe), Rickettsia spp. (Mediterranean basin, sub‑Saharan Africa), and Babesia spp. (northeastern United States, parts of Asia).
Duration of stay and activities performed outdoors, especially hiking, camping, or wildlife observation, which increase contact with vegetation where ticks quest.
Timing of the trip relative to symptom onset; incubation periods for tick‑borne diseases range from days to weeks, making recent travel a critical clue.
Use of protective measures (e.g., repellents, clothing) and any reported removal of a tick during the journey, even if the specimen was not retained.

When a patient reports travel to high‑risk areas and presents with a localized rash, fever, or flu‑like symptoms, the absence of a visible tick should not dismiss the possibility of a tick bite. Laboratory testing for specific antibodies or PCR assays can be ordered based on the geographic exposure indicated by the travel record. Early recognition, informed by travel details, enables prompt treatment and reduces the risk of complications.

Other Relevant Medical Conditions

When a tick is no longer attached, clinicians must evaluate alternative diagnoses that produce comparable skin lesions, systemic signs, or laboratory abnormalities. The differential includes both tick‑borne infections and unrelated conditions that can masquerade as a recent arthropod bite.

Key tick‑borne illnesses to consider:

Lyme disease – erythema migrans expanding >5 cm, often with central clearing; possible flu‑like symptoms, facial nerve palsy, arthralgia.
Rocky Mountain spotted fever – febrile illness with a maculopapular rash that may involve wrists and ankles; possible headache, nausea, and thrombocytopenia.
Ehrlichiosis and anaplasmosis – fever, headache, myalgia, and a non‑specific rash; laboratory findings often show leukopenia and elevated liver enzymes.
Babesiosis – hemolytic anemia, fever, and fatigue; peripheral blood smear reveals intra‑erythrocytic parasites.
Tularemia – ulceroglandular lesion with regional lymphadenopathy; may follow a tick bite but also occurs after handling infected animals.

Conditions unrelated to ticks that can mimic these presentations:

Allergic contact dermatitis – localized erythema and itching after exposure to plants or chemicals; no systemic fever.
Cellulitis – spreading erythema, warmth, and tenderness; usually accompanied by leukocytosis and responds to antibiotics targeting skin flora.
Other arthropod bites – spider, flea, or mosquito bites produce papules or wheals; often multiple and confined to exposed areas.
Viral exanthems – measles, rubella, or parvovirus B19 generate maculopapular rashes with systemic symptoms; laboratory serology distinguishes them.
Autoimmune vasculitis – palpable purpura and systemic involvement; antineutrophil cytoplasmic antibodies aid diagnosis.

A systematic approach—clinical history, physical examination, targeted laboratory testing, and, when indicated, imaging—allows clinicians to differentiate a prior tick exposure from these alternative medical conditions.