Transient Abnormal Myelopoeisis and Mosaic Down Syndrome in a Phenotypically Normal Newborn

Clinical characterization and genetic analysis of transient abnormal myelopoiesis without the down syndrome phenotype

Background

Transient abnormal myelopoiesis (TAM) is a congenital leukemia specific to neonates with Down syndrome (DS) or trisomy 21. However, rare cases of TAM can also occur with acquired trisomy 21 mutations or mosaic trisomy 21, leading to potential misdiagnosis due to the absence of the DS phenotypes.

Method

We present a case of TAM in a neonate without typical DS phenotypic features. We documented medical records from hospitalizations and a one-year follow-up period. Additionally, through a literature review, we summarized the clinical phenotype and genotypic characteristics observed in similar neonates.

Results

Despite the lack of typical DS phenotype the neonate was diagnosed with TAM upon detection of trisomy 21 and the GATA1 gene mutation, the condition resolved spontaneously without requiring chemotherapy. We monitored the neonate for a full year, during which no hematologic or developmental abnormalities were observed. Thirteen previous cases of neonates with TAM but without the DS phenotype have been reported. During the onset of TAM, the presence of trisomy 21 can be detected in peripheral blood cells or bone marrow cells, but some patients may not show evidence of trisomy 21 in fibroblasts. In these patients, trisomy 21 in peripheral blood cells or bone marrow cells may gradually decrease and even disappear as TAM improves. All patients experienced self-limiting remission with a favorable prognosis, although one case progressed to myeloid leukemia associated with DS by age two.

Conclusions

A negative obstetrical diagnosis and the absence of clinical DS phenotype should not preclude the consideration of TAM in neonates, especially when trisomy 21 mutations are detected.

Bullous eruptions in transient abnormal myelopoiesis with normal phenotype

Cutaneous lesions are common manifestation of congenital leukaemia especially myeloid type with incidence of 25%-50% in reported cases. It is relatively rare in transient abnormal myelopoiesis (TAM) seen in trisomy 21 (~10%). The rashes seen in leukaemia and TAM are different. We report a case with a rare presentation of confluent bullous eruption in a phenotypically normal neonate with trisomy 21 restricted to haematopoietic blast cells. This rash resolved rapidly after low-dose cytarabine therapy with normalisation of total white cell counts. The risk of Down syndrome-associated myeloid leukaemia in such cases is still high (19%-23%) in first 5 years and rare thereafter.

Transient myeloproliferative disorder as the presenting feature for mosaic trisomy 21

Trisomy 21 is a common congenital disorder with well-documented clinical manifestations, including an increased risk for the transient myeloproliferative disorder as a neonate and leukemia in childhood and adolescence. Transient myeloproliferative disorder is only known to occur in hematopoietic cells with trisomy 21. Children with mosaic trisomy 21 also have a risk for hematological malignancies. We present a nondysmorphic neonate, with a negative noninvasive prenatal screening of maternal blood for trisomy 21, who came to medical attention because of ruddy skin. He was found to have mild polycythemia, thrombocytopenia, and developed peripheral blasts. His clinical presentation was consistent with transient myeloproliferative disorder, which is only seen with trisomy 21. Cytogenetic studies of peripheral blood are positive for mosaic trisomy 21.

Recommendations for Diagnosis and Treatment of Children with Transient Abnormal Myelopoiesis (TAM) and Myeloid Leukemia in Down Syndrome (ML-DS)

Children with Down syndrome are at a high risk of developing transient abnormal myelopoiesis (TAM; synonym: TMD) or myeloid leukemia (ML-DS). While most patients with TAM are asymptomatic and go into spontaneous remission without a need for therapy, around 20% of patients die within the first six months due to TAM-related complications. Another 20-30% of patients progress from TAM to ML-DS. ML-DS patients are particularly vulnerable to therapy-associated toxicity, but the prognosis of relapsed ML-DS is extremely poor - thus, ML-DS therapy schemata must strive for a balance between appropriate efficacy (to avoid relapses) and treatment-related toxicity. This guideline presents diagnostic and therapeutic strategies for TAM and ML-DS based on the experience and results of previous clinical studies from the BFM working group, which have helped reduce the risk of early death in symptomatic TAM patients using low-dose cytarabine, and which have achieved excellent cure rates for ML-DS using intensity-reduced treatment protocols.

Cytogenetics of Pediatric Acute Myeloid Leukemia: A Review of the Current Knowledge

Pediatric acute myeloid leukemia is a rare and heterogeneous disease in relation to morphology, immunophenotyping, germline and somatic cytogenetic and genetic abnormalities. Over recent decades, outcomes have greatly improved, although survival rates remain around 70% and the relapse rate is high, at around 30%. Cytogenetics is an important factor for diagnosis and indication of prognosis. The main cytogenetic abnormalities are referenced in the current WHO classification of acute myeloid leukemia, where there is an indication for risk-adapted therapy. The aim of this article is to provide an updated review of cytogenetics in pediatric AML, describing well-known WHO entities, as well as new subgroups and germline mutations with therapeutic implications. We describe the main chromosomal abnormalities, their frequency according to age and AML subtypes, and their prognostic relevance within current therapeutic protocols. We focus on de novo AML and on cytogenetic diagnosis, including the practical difficulties encountered, based on the most recent hematological and cytogenetic recommendations.