The only clinical manifestation of a PAX5 mutation described to date is acute lymphoblastic B-cell leukemia or pre-B-ALL. In all of the patients, the leukemia was diagnosed during childhood, which suggests that the risk of developing B-ALL is significantly reduced after the first decade of life.
PAX5 deficiency exhibits incomplete penetrance, meaning that carriers of the PAX5 mutation may be healthy – in other words, they may not be affected by B-ALL. It is not yet known how high the probability is that a PAX5 mutation carrier will develop leukemia.
Other diseases of the blood-formation system or tumors affecting other organs have not to date been associated with PAX5 mutations.