The present case report features a highly uncommon form of a paediatric TCF3-HLF positive
acute lymphoblastic leukaemia (ALL) relapse, an extramedullary, peripheral bone manifestation.
Following complete remission, during the conditioning for haematopoietic stem cell
transplantation (HSCT), our sixteen-year-old male patient complained of fever, pain
and swelling of the right forearm. Radiography suggested acute osteomyelitis in the
right ulna with subsequent surgical confirmation. Intraoperatively obtained debris
culture grew Staphylococcus aureus and Acinetobacter pittii. Measures taken to control
the infection were deemed to be successful. However, after the completion of the otherwise
uneventful HSCT, a very early medullary relapse was diagnosed. Revising the original
surgical samples from the ulna, bone relapse of ALL was immunohistochemically confirmed.
Reviewing the previous cases found in the literature, it is advised to consider uncommon
forms of ALL relapse when encountering ambiguous cases of osteomyelitis or arthritis
during haematological remission.
