Ring chromosome 21 syndrome is an autosomal anomaly characterized by variable clinical features, most commonly including growth retardation, developmental delay, intellectual disability, epilepsy, microcephaly, short stature, dysmorphic features, hypogammaglobulinemia, thrombocytopenia and unspecific skeletal anomalies (hemivertebrae, clinodactyly, syndactyly). In rare cases, it has been described in phenotypically normal individuals. [from
ORDO]