Acute undifferentiated leukemia (AUL) is a type of leukemia where the immature blasts do not belong to a specific cell lineage, and originate from the hematopoietic stem cell. AUL is a subtype of acute leukemias of ambiguous lineage (ALAL).
Acute undifferentiated leukemia (AUL) is a form of acute leukemia of ambiguous lineage (ALAL). In these types of leukemia, there is no distinct cell lineage, either lymphoid or myeloid, with some cells expressing characteristics of more than one cell type. In AUL, the cancer cells cannot be assigned to a specific lineage. Genetic correlation has yet to be ascertained. Due to the rarity of the disease, its natural history and prevalence are not known  . Furthermore, AUL and other ALALs have no distinct features, and so cannot be distinguished clinically.
AUL is thought to originate from immature or poorly differentiated hematopoietic stem cells. These blast cells cannot be classified as they do not display lineage specific markers. AUL is seen in various age groups, but is most frequent after the 6th decade. Leukemias that present during this time period are associated with a poor prognosis, with a five year survival rate as low as 3% .
AUL presents similarly to other acute leukemias, typically with anemia and several bleeding diatheses. Bleeding may be from the skin, gastrointestinal tract and reproductive system, evidenced by epistaxis, petechiae, ecchymosis, hematuria, and abnormal uterine bleeding. Additional symptoms such as weight loss, malaise, fever and fatigue may be experienced. Individuals may also present with infections, which can be severe. They are more susceptible to infection due to the reduced production of normal white blood cells.
The diagnosis of acute undifferentiated leukemia is one of exclusion. Although AUL cannot be clinically differentiated from other types of acute leukemia, there are several techniques that are available for diagnosis. These include:
These tests are used to identify lineage-specific markers, which are lacking in AUL. Leukemic blast cells in AUL express markers that are non-specific. Often, AULs express cluster of differentiation (CD) markers CD7, CD13, and human leukocyte antigen-D related (HLA-DR)  .
Investigations carried out for acute leukemia include: