Limitations of G-banding Karyotype Analysis with Peripheral Lymphocytes in Diagnosing Mixed Gonadal Dysgenesis

Mixed gonadal dysgenesis (MGD) is an abnormal sexual differentiation syndrome usually presenting with ambiguous genitalia. Karyotype analysis is one of the essential components in the diagnosis of MGD and is conventionally done with peripheral lymphocytes by the G-banding technique. It is speculated that this conventional karyotype analysis has limitations since there are often difference in gonadal tissue analysis. Here we present four cases of MGD, in which karyotype analysis were performed by peripheral lymphocytes fluorescence in situ hybridization (FISH), gonad fibroblasts FISH and gonad fibroblasts G-banding technique, in addition to the conventional peripheral lymphocytes G-banding technique. In Case 1, the percentage of the 45,X cell line in lymphocytes decreased after birth and detection of mosaicism could only be done by karyotype of gonads at 7 mo of age. In Case 2, FISH analysis with peripheral lymphocytes was more useful for detecting low frequency mosaicism. In all cases, phenotype of gonads and external genitalia were more consistent with karyotype of gonads than that of the peripheral lymphocytes G-banding technique. In conclusion, conventional G-banding karyotype analysis with peripheral lymphocytes has limitations in the diagnosis and evaluation of MGD. Karyotype analysis by FISH or by using gonads is useful for diagnosing MGD and understanding of the phenotype of gonadal tissue.