The aim of the study is to improve the accuracy of diagnosis for children and adolescents with MDS by a standardized review of morphology and standardized cytogenetic and molecular analysis.

The primary objectives of the study are:

• To evaluate the frequency of the different subtypes of MDS in childhood and adolescence by a standardized diagnostic approach
• To evaluate the frequency of cytogenetic and molecular abnormalities:

Specifically using array-CGH to evaluate the frequency of subtle chromosomal imbalances, i.e. gains and losses of defined chromosomal regions, and amplifications.

Specifically using mFISH to identify unknown chromosomal aberrations, particularly subtle translocations involving new candidate genes, and to better define chromosomal breakpoints.

The secondary objectives of the study are:

• To assess survival for children and adolescents with MDS and JMML
• To evaluate relapse rate, morbidity and mortality in children with MDS and JMML treated by HSCT

Inclusion Criteria:

• Written informed consent by the caretakers and whenever possible the patient's assent.
• Confirmed diagnosis of MDS or JMML (morphology, cytogenetics)
• Myeloid leukemia of Down syndrome (patients aged > 6 years).
• Age less than 18 years

Exclusion Criteria:

• Denied informed consent and/or assent by caretakers/patient.
• Myeloid leukemia of Down syndrome (patients < 6 years).
• Participation in another study within the last 4 weeks (except for therapy optimizing studies in cancer or bone marrow failure disorders and studies in diagnostics).

MDS and JMML diagnosted