The usefulness of detection of sex chromatin in babies with uncertain sex in resource limited settings

Ambiguous genitalia in a new born baby is a major problem to the health care worker as well as the family of the affected (1). To minimize psychosocial problems that may arise in the families of affected babies, early detection and quick determination of the sex of the individual is essential (1, 2). The gold standard for such cases in karyotyping, and this may pose a problem since access to chromosomal analysis is not readily available to all institutions. Identification of sex chromatin is a simple first line investigation that can be used in resource limited settings. The term 'sex chromatin' is used to describe two structures namely the Barr body, present in epithelial and other tissue cells and the drumstick chromosome of the polymorphonuclear leucocytes (3,4,5). The Barr body was described by Dr. Murray Barr in 1949 and is produced by the inactivation of the X chromosome as explained in the Lyon h y p o t h e s i s ( 3 , 6 ) . D r u m s t i c k chromosome is also produced by the same inactivation mechanism but is seen in 3 out of 100 circulating neutrophils in the blood of normal females (4). The Barr body examination in a buccal smear a n d i d e n t i f y i n g t h e d r u m s t i c k chromosome in a peripheral blood smear are relatively simple and inexpensive tests and can give the clinician an idea about the chromosomal sex of the baby when karyotyping is unavailable.