Back, Joint, and Extremity Pain - Case 5-2: 2-Year-Old Boy
I. History of Present Illness
A 2-year-old boy presented with a 2-week history of difficulty walking. The
parents had noticed that he would no longer run while playing with his
siblings. Over the past week, he had begun walking with a limp and refusing to
climb stairs. His pediatrician detected splenomegaly and tenderness over the
right hip. There was no fever, cough, rhinorrhea, throat pain, diarrhea, or
trauma. There had been no ill contacts. A pet dog was acquired 1 week earlier.
Hip radiographs and several laboratory studies were obtained, after which the
patient was immediately referred to the emergency department.
II. Past Medical History
The patient was born at term without complications. He had been hospitalized
with wheezing at 4 months of age and required oral antibiotics at 12 months of
age for outpatient treatment of pneumonia. He was not receiving any medications
and had no allergies. Family history was remarkable for a maternal aunt with
rheumatic heart disease.
III. Physical Examination
T, 37.3°C; RR, 34/min; HR, 104 bpm; BP, 98/43 mm Hg
Height and weight, both 25th percentile for age
On examination, the child was pale and tired-appearing. His sclerae were
anicteric. The heart and lung sounds were normal. The spleen tip was palpable
just below the left costal margin. The liver edge was palpable 3 cm below the
right costal margin. There was mild discomfort with passive flexion of the
right hip, but the range of motion was normal. There was no overlying erythema
or warmth. Examination of the left hip was unremarkable. The testes were in
normal position and were not enlarged, swollen, or tender. Numerous petechial
lesions were scattered on his lower extremities bilaterally. Small lymph nodes
were palpable in the anterior cervical and inguinal regions.
IV. Diagnostic Studies
The complete blood count revealed 4,300 WBCs/mm3, with 3% band forms, 8% segmented neutrophils, and 85% lymphocytes, giving an
absolute neutrophil count of 473/mm
3. The hemoglobin was 8.0 g/dL, with a reticulocyte count of 1.3%. The platelet
count was 31,000/mm
3. CRP and ESR were 2.6 mg/dL and 60 mm/hour, respectively. Serum lactate
dehydrogenase (LDH), uric acid, transaminases, and electrolytes were normal.
The hip radiographs performed earlier were reviewed (Fig. 5-2A).
V. Course of Illness
Results of the hip radiography, combined with results of the peripheral blood
smear (see Fig. 5-2B), suggested a diagnosis.
Discussion: Case 5-2
I. Differential Diagnosis
Infectious causes of hip pain in a young boy include septic arthritis of the
hip, osteomyelitis of the femur or pelvis, and psoas abscess. The prolonged
duration of symptoms with recent worsening, in conjunction with an elevated CRP
and ESR, may indicate osteomyelitis of the femur with extension of infection
into the hip joint. However, the relatively unimpressive amount of pain on hip
examination, combined with pancytopenia, makes infectious causes unlikely.
Toxic synovitis can cause hip pain in this age group but also is not typically
associated with pancytopenia.
Causes of pancytopenia, hepatosplenomegaly, and bone pain include leukemia,
epiphyseal tumors, neuroblastoma, infectious mononucleosis, and hemophagocytic
syndrome. The normal uric acid and LDH do not exclude malignancy.
II. Diagnosis
The hip radiographs revealed dense metaphyseal lines bilaterally with adjacent
metaphyseal lucency, a finding suggestive of leukemia (see Fig. 5-2A). The
peripheral blood smear revealed numerous cells with scant cytoplasm and finely
dispersed to variably condensed chromatin, morphologically consistent with
lymphoblasts (see Fig.5-2B). Morphologic, cytochemical, and immunophenotypic
features of the bone marrow aspirate were diagnostic of acute lymphocytic
leukemia. The child was initially treated with vincristine, dexamethasone, and
intrathecal ara-C.
III. Epidemiology
Leukemia results from malignant transformation and clonal expansion of
hematopoietic cells that have stopped at a particular stage of differentiation
and are unable to progress to more mature forms. Leukemias are divided into
acute and chronic subtypes and are further classified on the basis of leukemic
cell morphology into lymphocytic leukemias (lymphoid lineage cell
proliferation) and nonlymphocytic leukemias (granulocyte, monocyte,
erythrocyte, or platelet lineage cell proliferation). Acute leukemias
constitute more than 95% of all childhood leukemias and are subdivided into
acute lymphocytic leukemia (ALL) and acute nonlymphocytic leukemia, also known
as acute myelogenous leukemia (AML). The following discussion focuses on ALL.
ALL, the most common pediatric malignancy, accounts for approximately 25% of all
childhood cancers and 75% of all childhood leukemias. Most children are
diagnosed between 2 and 5 years of age. In the United States, the incidence of
ALL is higher in whites than in blacks and in boys than in girls. Genetic
factors also affect the risk of ALL. ALL develops in siblings of children with
ALL two to four times more often than in unrelated children. The concordance of
ALL in monozygotic twins is approximately 25%. Children with chromosomal
abnormalities, including trisomy 21, and syndromes characterized by chromosomal
fragility, such as Bloom
's syndrome and Fanconi anemia, also have a substantially higher risk of
leukemia.
IV. Clinical Presentation
The presenting symptoms and signs of children with ALL reflect the degree of
bone marrow infiltration with leukemic cells and the extent of extramedullary
disease spread. Symptoms may be present for days or months and include fever,
anorexia, fatigue, and pallor. Bone pain occurs with leukemic involvement of
the periosteum and bone. Young children often develop a limp or refuse to walk.
Headache, vomiting, and seizures suggest CNS involvement. Rarely, children
present with oliguria due to acute renal failure precipitated by hyperuricemia.
On examination, painless lymphadenopathy (50%) and hepatosplenomegaly (68%)
result from extramedullary spread of the disease. Petechiae and purpura are
more common, but some children also have subconjunctival and retinal
hemorrhages. Children may have focal bone tenderness. Testicular enlargement
due to leukemic infiltration is present in 5% of boys with ALL.
V. Diagnostic Approach
Complete blood count. The WBC count is between 10,000 and 50,000 cells/mm3 in 30% of children with ALL and greater than 50,000 cells/mm3 in approximately 20%. Neutropenia, defined as an absolute neutrophil count less
than 500 cells/mm
3, is common at presentation. Other findings include moderate to severe anemia
and an inappropriately low reticulocyte count. The platelet count is less than
100,000 cells/mm
3 in approximately 75% of patients, but isolated thrombocytopenia rarely occurs.
The severity of bleeding correlates with the degree of thrombocytopenia.
Leukemic cells may be noted on the peripheral blood smear, particularly if the
WBC count is normal or high.
Bone marrow aspirate or biopsy. A bone marrow aspirate or biopsy definitively establishes the diagnosis of ALL,
because the morphology of blasts seen on peripheral smear may not reflect the
true bone marrow morphology. Monoclonal antibody testing of the bone marrow for
specific cell surface antigens identifies lymphocytes and granulocytes at
different stages of development. When this immunophenotyping is combined with
cytochemical staining and molecular genotyping, the diagnostic classification,
treatment, and prognosis become more specific.
Other laboratory studies. Other laboratory abnormalities reflect either leukemic cell infiltration or
excessive proliferation and destruction of leukemic cells. Serum transaminases
may be mildly abnormal with liver infiltration, but coagulation abnormalities
are uncommon. Hypercalcemia results from leukemic infiltration of bone.
Increased serum phosphorus levels occur as a result of leukemic cell lysis and
may induce hypocalcemia. Cell lysis also leads to elevated serum uric acid
concentrations, reflecting increased purine catabolism, and elevated LDH.
Radiographs. Long bone radiograph abnormalities include transverse radiolucent metaphyseal
growth arrest lines, periosteal elevation with reactive subperiosteal cortical
thickening, and osteolytic lesions.
Computed tomography. Computed tomography may reveal diffuse lymphadenopathy and hepatosplenomegaly.
Approximately 5% to 10% of newly diagnosed patients have an anterior
mediastinal mass detected on chest imaging.
VI. Treatment
Although specific treatment strategies vary from center to center, all modern
approaches treat the complications of ALL at presentation, treat the leukemia,
and manage treatment-related complications. Acute management involves blood
product transfusions and treatment of infection, hyperviscosity, compressive
symptoms, and metabolic abnormalities. The term
tumor lysis syndrome describes the constellation of metabolic abnormalities resulting from
spontaneous or treatment-induced tumor necrosis. Acute tumor cell destruction
releases intracellular contents into circulation, leading to hypocalcemia,
hyperphosphatemia, hyperkalemia, and hyperuricemia. Management of tumor lysis
syndrome includes vigorous hydration, urine alkalinization, uric acid
reduction, and diuretic therapy.
Specific therapy for ALL is instituted in three distinct phases. Remission induction therapy lasts approximately 4 weeks, during which most children have a complete
remission (defined as the absence of clinical signs and symptoms of disease),
recovery of normal blood cell counts, and recovery of normocellular bone
marrow. Agents currently used for remission induction include dexamethasone or
prednisone, vincristine, and
l-asparaginase. Other agents may be used if the patient is considered to be at
high risk or has CNS involvement.
Consolidation therapy aims to kill additional leukemic cells with further systemic therapy and to
prevent CNS relapse with intrathecal chemotherapy.
Maintenance therapy aims to continue remission achieved by the first two phases; it is required
because shorter treatment protocols are associated with a high rate of relapse.
Methotrexate and 6-mercaptopurine are often used for consolidation and
maintenance therapy.
Children with high WBC counts (greater than 50,000/mm3) and those who are younger (less than 2 years of age) or older (greater than 10
years of age) at diagnosis have the worst prognosis. However, between 95% and
98% of children diagnosed with ALL achieve complete remission after induction
therapy. Relapse occurs in 20% to 30%, either during subsequent treatment or
within the first 2 years after its completion. Relapse can affect virtually any
site of the body, although bone marrow relapse is most common. Since the
introduction of effective CNS-directed therapy, the frequency of CNS relapse
has decreased to approximately 5%. Isolated testicular relapse occurs in 1% of
boys. Bone marrow relapse is often treated with intense chemotherapy combined
with bone marrow transplantation. The event-free survival rate after relapse
ranges from 30% to 60%.
Late sequelae of ALL therapy include second neoplasms, neuropsychologic effects,
endocrine dysfunction, and other organ-specific complications. Second neoplasms
occur in 2.5% of patients; CNS tumors are the most common second neoplasm.
Children who are younger than 5 years of age at ALL diagnosis and those who
receive cranial irradiation are at highest risk. Short stature occurs due to
cranial irradiation
–induced growth hormone deficiency. Some late complications are related to
specific chemotherapeutic agents, such as cardiomyopathy from anthracycline or
bladder fibrosis from cyclophosphamide therapy. Chemotherapy may also have
long-term effects on the child
's immune system. Recovery of the immune system usually occurs within 1 to 2
years after the completion of chemotherapy. However, some children have low
antibody titers of clinically significant viruses to which they have been
previously immunized.
VII. References
1. Hermiston ML, Mentzer WC. A practical approach to the evaluation of the
anemic child.
Pediatr Clin North Am 2002;49:877–891.
2. Margolin JF, Poplack DG. Acute lymphoblastic leukemia. In: Pizzo PA, Poplack
DG, eds.
Principles and practice of pediatric oncology, 3rd ed. Philadelphia: Lippincott–Raven, 1997:409–462.
3. Meister LA, Meadows AT. Late effects of childhood cancer therapy. Curr Probl Pediatr 1993;23:102–131.
4. Neglia JP, Meadows AT, Robison LL, et al. Second neoplasms after acute
lymphoblastic leukemia in childhood.
N Engl J Med 1991;325:1330–1336.
5. Pui CH, Crist WM. Biology and treatment of acute lymphoblastic leukemia. J Pediatr 1994;124:491–503.
6. Rubnitz JE, Look AT. Molecular genetics of childhood leukemias. J Pediatr Hematol Oncol 1998;20:1–11.
7. Sanders JE. Bone marrow transplantation for pediatric leukemia. Pediatr Ann 1991;20:671–676.
Pictures
Book Source Details
- Book Title: Pediatric Complaints and Diagnostic Dilemmas
- Author(s): Samir S Shah MD; Stephen Ludwig MD
- Year of Publication: 2003
- Copyright Details: Pediatric Complaints and Diagnostic Dilemmas, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright Details: Pediatric Complaints and Diagnostic Dilemmas, Copyright © 2008 Williams & Wilkins.
More About Causes of Back pain
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