Patient with rheumatoid arthritis and MCA/MR syndrome due to unbalanced der(18) transmission of a paternal translocation t(18;20)(p11.1;p11.1).

A girl with psychomotor retardation and a pattern of minor anomalies was found to have a slightly enlarged short arm of chromosome 18 by conventional GTG-banded chromosome examination. The 18p+chromosome has also been found in the father. FISH studies using chromosome 18-and chromosome 20-specific painting probes confirmed a reciprocal whole arm translocation between chromosomes 18 and 20 in the father, resulting in monosomy of the short arm of chromosome 18 and trisomy of the short arm chromosome 20 in the patient. FISH analysis using a chromosome 18 alpha-satellite-specific probe showed a reduced signal intensity. The patient presented with a flat, oval face, upslanting palpebral fissures, periorbital fullness, and mental retardation; she also had chronic diarrhea with milk protein intolerance and juvenile rheumatoid arthritis at age 5 years. Juvenile rheumatoid arthritis, like several other immunologic disorders, has occasionally been reported in patients with deletion of 18p, and thus most likely loss of a gene or genes on 18p is responsible for various immunologic disorders occurring in these patients.