Study of Blood Samples From Newborns With Down Syndrome

Inclusion Criteria:

* Diagnosis of transient myeloproliferative disorder (TMD) at \< 90 days of age and meeting 1 of the following criteria:

* A diagnosis of Down syndrome or Down syndrome mosaicism AND non-erythroid and non-lymphoid blasts (any amount) in the peripheral blood verified with a second sample

* Patients with typical physical characteristics of Down syndrome are allowed before cytogenetic or FISH confirmation of the diagnosis
* Trisomy 21-positive leukemic blasts documented by biopsy of any organ (including \> 5% non-erythroid/non-lymphoid blasts documented by bone marrow aspirate or biopsy)

* Infants with isolated trisomy 21 positivity identified only in the leukemic blasts are allowed
* Institutional immunophenotype characterization is required for study enrollment