Thai girl with ring chromosome 18 (46XX, r18).

Chromosomal anomalies occur in 0.4% of live births. Ring chromosomes have been found for all human chromosomes and when it is replacing a normal chromosome, it results as a partial monosomy. The phenotype often overlaps that seen in comparable deletion syndromes of the same chromosomes. In the present report the authors describe the clinical manifestations of a girl with ring chromosome 18 (46XX,r18) including dysmorphic features, failure to thrive, global delay of development, hypothyroidism, atopic dermatitis, bilateral chronic otitis media, aortic regurgitation with patent foramen ovale and immunoglobulin A deficiency.