RESULTS & CASE DESCRIPTION
A 7-year-old male presented with left knee swelling, generalized
petechiae, and severe thrombocytopenia. The patient was previously
healthy with no recent illnesses, medications, or trauma. Two weeks
before presentation, he developed petechiae that progressed to cover his
torso and extremities. Three days before presentation, he developed
swelling of the left knee with restricted range of motion and limping. A
complete blood count (CBC) performed on the day of presentation showed
platelets of 6 x 10*3/uL with otherwise normal hemoglobin, red blood
cell indices, and white blood cell count. There was no known tick
exposure but Lyme serologies were obtained. The patient was sent to the
emergency department.
Initial exams showed petechiae on the palate, torso, and all four
extremities with swelling of the left knee (Image 1) leading to
decreased range of motion and weight bearing. The family denied patient
or family history of easy bleeding or bruising disorders. Laboratory
evaluation was significant for platelet count of 4 x 10*3/uL, immature
platelet fraction of 22.2% (Ref. range and units: 1.1% – 8.5%),
prolonged activated partial thromboplastin time (aPTT) of 47s. (Ref.
range and units: 24 – 36 seconds), normal prothrombin time (PT) of
14.7s. (Ref. range and units: 12.4 – 14.7 seconds), fibrinogen 460
mg/dL (Ref. range and units: 170 – 410 mg/dL). Due to prolonged aPTT,
mixing studies were completed to rule out a coagulation factor
deficiency or inhibitor. Quantitative Factor XII, XI, VIII, and IX
levels were normal. An ultrasound showed an echogenic joint effusion
distending the knee capsule (Image 2) consistent with left knee
hemarthrosis. Patient was admitted for further management.
On hospital day one, peripheral blood smear showed findings consistent
with ITP. X-rays showed no fracture or traumatic findings. Intravenous
immunoglobulin (IVIG) and steroids were initiated due to severe
thrombocytopenia with hemarthrosis. On hospital day two, the patient
demonstrated improved knee swelling and range of motion along with
improved platelet count to 29 x 10*3/uL. Arthrocentesis and additional
imaging were deferred given clinical improvement. The Lyme Disease
screening assay resulted positive (Ref. range and units: Negative, a
positive screen result is considered presumptive positive for Lyme
Disease with confirmatory immunoblot sent). Repeat screening assay and
confirmatory immunoblot were obtained but empiric antibiotics were not
started.
Two days following hospital discharge, repeat Lyme Disease screening
resulted positive for IgM and IgG and a 28-day course of doxycycline was
prescribed. Patient was seen by infectious diseases and hematology five
days after hospital discharge. He had no ongoing bleeding symptoms and
near resolution of knee swelling and pain. Initial immunoblot testing
resulted in positive IgM bands 3/3 and IgG bands 9/10 (Ref. range and
units: Lyme Disease IgM immunoblot requires reactivity to 2 of 3
specific borrelial proteins to be considered positive, Lyme Disease IgG
immunoblot must show reactivity to at least 5 of 10 specific borrelial
proteins to be considered positive). Stronger consideration was given to
Lyme arthritis as contributive to clinical presentation. At final follow
up, evaluation showed a robust platelet response to 738 x 10*3/uL
without evidence of recurrent symptoms.