Chromosome 21 monosomy syndrome. 21 deletion syndrome. Monosomy 21.
Incidence
Very rare syndrome. Sporadic. The syndrome is generally lethal and only several cases of living newborn infants have been reported, most of whom die between 3 weeks and 20 months of life.
Clinical Characteristics
Monosomy 21 is a chromosome anomaly due to partial or complete deletion of chromosome 21. Patients present with peculiar facies, microcephaly, growth retardation, severe mental retardation, and stiff joints. The absence of one chromosome of one pair in an otherwise diploid chromosome 21. The syndrome is characterized by developmental retardation in association with craniofacial, skeletal, genital, cardiac, and other anomalies. The phenotype shares some similarities with the chromosome 21q deletion syndrome.
Precipitants
None
Provocation Tests
None
Diagnostic Procedures
Karyotype. There is a chromosome anomaly due to partial or complete deletion of chromosome 21.