Monosomy 21 Mosaicism in a Child with Dyserythropoiesis

All complete monosomy 21 appear to be lethal early in their development in humans and only survive in mosaic forms. Complete monosomy 21 is a very rare and usually debilitating genetic disorder. Partial monosomy 21 is also rare and is thought to constitute a clinical syndrome consisting of peculiar faces, hypertonia, psychomotor retardation, and slow growth. We experienced a case of monosomy 21 mosaicism. Chromosome analysis demonstrated mosaicism for cell lines in the lymphocytes examined; 45, XX, -21/46, XX. The main clinical features were craniofacial dysmorphism including high arched palate, submucosal cleft, micrognathia and arthrogryposis-like symptoms including flexion deformity of fingers. And hematological findings were revealed dyserythropoiesis, thrombocytopenia and eosinophilia. Currently, the patient has nearly compatible growth, but a mild degree of mental retardation. We report here an 8 years old female child with apparent monosomy 21 mosaicism associated with dyserythropoiesis, thrombocytopenia and eosinophilia, with a review of the associated literatures.

A Case of 21-Monosomy with Holoprosencephaly(Semilobar Type)

Holoprosencephaly of unknown definite causes, has been associated with several chromosome abnormalities involving the autosomes and the sex chromosomes. The most commonly reported associations include dup(3p), del(7q), deletions of chromosome 13, trisomy 13, trisomy 18, and triploidy. In previously reported cases in Korea, none were associated with chromosome 21 anomalies. In conclusion, we reported the first case of holoprosencephaly(semilobar type) associated with pure monosomy 21. We experienced a semilobar type holoprosencephaly with monosomy 21 in a neonate who had multiple congenital anomalies, including an abnormal face, a small thorax with widely spaced hypoplastic nipples and nail hypoplasia, lung hypoplasia with severe scoliosis and cardiac abnormalities. Chromosomal analysis revealed a 45, XY, -21.