Letter: Developmental mixoploidy and trisomy-20 syndrome

Direct karyotyping of unstimulated newborn blood: a rapid diagnostic method for the clinical management of critically ill newborns

Using spontaneously dividing nucleated erythrocytes present in newborn cord and peripheral blood, we performed direct karyotype analysis on a cohort of 162 infants suspected of chromosome abnormalities. A cytogenetic diagnosis was obtained in 149 cases (91.9%). In all cases conventional phytohaemagglutinin- (PHA)-stimulated cultures were used for comparison. Concordance between direct and stimulated karyotypes was seen in all but 5 cases. In these 5 cases, abnormalities were seen in the direct harvest while PHA-stimulated cultures showed normal results. Skin fibroblasts from 2 of these cases, available for follow-up, showed the abnormalities in a mosaic state. Our experience confirms that direct karyotyping of fetal and newborn blood is feasible, fast, and efficient and can provide accurate diagnosis of major chromosome abnormalities within 18-24 hours after obtaining the blood.

Tissue limited mosaicism for unbalanced autosomal translocation in a child with congenital anomalies and mental retardation

We studied a patient with a sporadic mental retardation/multiple congenital anomalies syndrome. Chromosome analysis showed a 46,XX, inv(9)(p 11;q13) karyotype in all lymphocytes. Fibroblasts from two separate skin biopsies revealed a mosaic karyotype. Some 22.5% of fibroblasts had a karyotype like that of the lymphocytes, while 77.5% of fibroblasts had a karyotype 46,XX,inv(9)(p11;q13),der(12),t(12;?)(P13;?). The data in this case emphasize the drawbacks of confining cytogenetic analysis to lymphocytes.