INTRODUCTION
Idiopathic thrombocytopenic purpura (ITP) is a blood disorder
characterized by immune-mediated antibody platelet
destruction1,2 .
ITP is categorized into primary, or idiopathic, and secondary if a cause
is identified such as a preceding viral illness or an underlying
immunodeficiency3.
The incidence rate of 1-6.4 cases per 100,000 children shows a biphasic
age distribution: toddlers and
adolescents4.
The result is a quantitative platelet deficiency available for primary
hemostasis manifesting as mucocutaneous bleeding (e.g., petechiae,
bruising, oral/buccal purpura, epistaxis). Severe presentations
including internal bleeding are rare in children and occur less
frequently than in
adults5.
A comparative prospective registry of 1,784 children newly diagnosed
with ITP reported the incidence of joint bleeding involvement as the
lowest of all organ
systems6.
Factors predictive for severe bleeding include severe thrombocytopenia
(platelet count < 20 x 10*3/uL, Ref. range and units: 142 –
508 x 10*3/uL), newly diagnosed ITP, and previous minor
bleeding6.
Hemarthrosis is defined as bleeding into a joint and can cause
monoarticular swelling and pain. The most common cause is trauma where
bleeding develops due to bone, soft tissue, or ligamentous injury.
Non-traumatic etiologies include bleeding disorders, osteoarthritis,
septic arthritis, bursitis, intra-articular vascular anomalies or tumors
such as synovial
hemangiomas7,8,9.
While prevalence rates of hemarthrosis in children with severe
hemophilia A or B can be as high as
33-47%10,
acute hemarthrosis in children without hemophilia is rare and typically
follows traumatic
injury8.
While imaging findings can be suggestive, definitive diagnosis is via
arthrocentesis for synovial fluid analysis. We present a case of
non-traumatic hemarthrosis in the setting of ITP where the patient was
found to have positive serologies for Lyme Disease.
Lyme Disease was first described as an arthritis in children that could
be monoarticular or oligoarticular. Typical presentation occurs in
stages with localized skin lesions followed by disseminated infection
days to weeks later with migratory joint
pain11.
Without antibiotic treatment, 60% of patients with Lyme Disease develop
arthritis involving one or many
joints12.
Progression to arthritis is a late disease manifestation resulting from
strains of Borrelia burgdorferi disseminating into the joint
space causing immune response with resultant
inflammation12.
Following antibiotics, spirochetes are destroyed, and inflammation of
the affected joints typically
resolves12.