Clonal Cytopenia of Unknown Significance (CCUS) is one of the conditions that can give rise to an unexplained hematologic disorder in an older adult. It may be associated with risk for progression to myelodysplastic syndrome (MDS).

Features of CCUS:

(1) older adult (typically >= 65 years of age)

(2) a cytopenia is present in one or more lineages

(3) clonal or molecular aberration: present (allelic burden >= 2% but < 10%)

(4) dysplasia: absent

(5) cytogenetic abnormalities: absent

(6) bone marrow blasts less than 5%

(7) not explained by other hematologic or non-hematologic disorder, especially MDS


The presence of multiple mutations increases the risk of progression to MDS.

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