Paediatric acute leukaemia

Introduction

• Leukaemias divided into:
  • Lymphoid (80%)
  • Myeloid: AML and CML (15% and 2% respectively)
• Together accounts for 1/3 of all malignancies in children
• Peak incidence ages 2-6yo

Clinical presentation

• Signs and symptoms of ALL and AML are similar and depend on degree of marrow infiltration and extent of extramedullary involvement
• Non-specific lethargy, bone pain and loss of appetite
• Acute leukaemia classically presents as:
  • Fever/infection, pallor, lethargy, bruising and mucosal bleeding due to febrile neutropaenia, anaemia and thrombocytopaenia collectively
• Marrow infiltration causes bone pain
• Extramedullary spread causes painless adenopathy (incl. mediastinal), hepatomegaly, splenomegaly, skin or periorbital infiltrates and rash
• CNS involvement in 4% of children (CN palsy, cord compression)
• Testicular leukaemia in 10% of boys (painless, enlarged testes)
• Hyperviscosity results in infarction (CNS, pulmonary) and rarely priapism

• AML tends to produce more extramedullary involvement with:
  • Gingival hyperplasia
  • Subcutaneous nodules
  • Blueberry muffin lesions
  • Chloromas
• Gingival hyperplasia in any child is AML until proven otherwise (even if no other symptoms)
• Chloromas often in periorbital region

Differential

• Pancytopaenia
  • Acute leukaemia
  • Aplastic anaemia
  • Marrow infiltration by non-haematological malignancy
  • Collagen-vascular diseases
  • Hepatosplenomegaly and adenopathy are rare in above Dx
  • Viral infections (adenopathy and hepatosplenomegaly with atypical lymphocytes vs. blast cells
  • Leukaemoid reactions with WCC >50 rarely occur in infection (e.g. pertussis) or inflammatory conditions
  • Isolated thrombocytopaenia may be post-infectious or ITP/TTP related

Investigations

• FBC reveals anaemia and thrombocytopaenia in 80% of cases
• Most children have WCC <20
• Those with raised WCC typically have extramedullary involvement
• Neutrophils often <1
• Circulating blast cells often seen on film
• BC positive in up to 25% of new leukaemia diagnoses
• CXR: mediastinal mass in 5-10%
• Bone marrow aspirate and trephine ultimately
• Do NOT need raised WCC on peripheral count for diagnosis (it is all about the bone marrow)
• AML rarely has a coagulopathy that can lead to DIC

Prognosis

• ALL cure rate 80%
• AML cure rate 30-50%
• Adverse prognostic factors
  • Age <1 or >10
  • Philadelphia translocation
  • High presenting leukocyte count
  • Poor response to first treatment
• Risk of ALL relapse is 15-20%
• Risk of second malignancies after successful treatment of ALL is low

Tumour lysis syndrome

• Massive cell death due to treatment
• Raised LDH, liver enzymes, hyperkalaemia, hyperuricaemia, hyperphosphataemia, hypocalcaemia and acute renal failure

Last Updated on November 20, 2021 by Andrew Crofton