Molecular screening for fragile X syndrome in Thailand.

Fragile X syndrome (FXS) is the most common form of inherited mental retardation. We screened for FXS in 237 Thai males (age < or = 15 years) with developmental delay of unknown cause. We found 16 (6.8%) to have FXS using standard molecular analysis. Wc then studied the extended families of these 16 FXS subjects and 4 other independently ascertained FXS cases. We found that there were at least 35 affected males and 8 affected females. In addition we found that there were at least 31 premutation carrier females and 4 premutation males. The CGG repeats numbers in these premutation individuals ranged from 60 to 125. By comparison, the normal CGG repeats were 19-50 with a heterozygosity of 67.2% in 337 randomly selected males. This study providcs insight into the high incidence of FXS in developmentally delayed Thai males and points the way toward the means of prevention of mental retardation by genetic counseling and prenatal diagnosis.

The frequency of fragile X syndrome among selected patients at Songklanagarind Hospital during 1991-1996, studied by cytogenetic and molecular methods.

Fragile X syndrome is the most common inherited form of mental disability, world-wide. Main clinical features are cognitive deficit, speech difficulties, delayed development, autism, and particular physical characteristics. The syndrome can be cytogenetically diagnosed by the expression of chromosome X fragile site at band Xq27.3. At molecular level, the cause of the syndrome is defined as an abnormal expansion of CGG trinucleotide repeats in the 5'UTR of the FMR-1 gene as well as hypermethylation at the proximal CpG island. Study of fragile X syndrome at Songklanagarind Hospital during May 1991-June 1996 was herein reported. A total of 287 blood samples of 260 unrelated families were cytogenetically examined by using lymphocyte culture method with 2-4 different treatments. Frequency of positive fragile X cases was found to be 7 in 260 (2.7%). Among relatives of the positive ones, 13 individuals were also positive. Other types of chromosome abnormalities were detected in 13 cases (5%). For molecular study, DNA samples were obtained from 97 cases. Investigation of CGG repeat expansion was performed by PCR method. Abnormal expansion was identified as full mutation (> 200 repeats) and premutation (> 50-200 repeats). The abnormalities were found in 14 individuals of 5 unrelated cases; 6 with full mutation and 8 with premutation. No molecular study on the two cytogenetic positive cases has been performed. In conclusion, a total of 50 individuals with fragile X abnormality has been documented: 18 affected cases and 32 carriers. Investigation of the remaining suspected members in positive families is in progress. The information and experience will lead to prevention of this genetic disease by prenatal diagnosis and elective abortion in Thailand.

An infant with Down-Turner double aneuploidy: a case report and literature review.

The case of an 8 month-old female infant with non-mosaic Down-Turner double aneuploidy is reported. She had Down facies without stigmata of Turner syndrome. A review of 22 previous reported cases revealed mosaicism in all cases, either 21 mosaic or X mosaic. Our patients is the first reported case of non-mosaic trisomy 21-monosomy X polysyndrome in Thailand.

True 47,XXX in a patient with premature ovarian failure: the first reported case in Thailand.

A case of triple-X female with premature ovarian failure was reported. The patient was a 23-year-old, single, Thai woman who presented with primary amenorrhea, incomplete development of the secondary sex characteristics, elevated levels of serum gonadotropins, and decreased estrogen concentration. Immunological abnormalities were not identified by antinuclear antibody, rheumatoid factor, antimicrosomal antibody and antithyroglobulin antibody studies. Cyclic estrogen-progestin was given and withdrawal bleeding occurred. The present case represents the utilization of chromosomal analysis in a patient with delayed sexual development, or primary amenorrhea and elevated serum gonadotropin levels.

True hermaphrodite, 46,XX/46,XY karyotype with surgical reconstruction of ambiguous genitalia: a case report and literature review.

A 17-year-old phenotypic female with ambiguous genitalia is presented. The patient complained of progressive dysmenorrhea, passing urine and menstrual blood through the same opening since menarche. Pelvic examination revealed and enlarged clitoris with prominent phallus, an enlarged right labio-scrotal fold with palpable gonad and a 3 mm diameter opening of both the urethral meatus and vaginal orifice at the vestibule. Chromosome analysis showed 46,XX/46XY karyotype. Laparotomy via right inguinal incision confirmed true hermaphroditism because of finding a right unilateral ovotestis. Factors leading to delay in presentation are discussed and the need for early diagnosis and management is emphasized. The clinical, cytogenetic features, gonadal histology and management are described and discussed.

Chromosome analysis of 894 patients.

Metaphase chromosome analysis from cultured blood lymphocytes was performed in 894 consecutive patients from the year 1981 to early 1989. G-bands by trypsin using Giemsa (GTG) was routinely employed during the last five years supplemented with other banding techniques if required. High resolution chromosome banding was performed in cases suspected of structural chromosome abnormality. Successful studies were obtained in 862 (96.4%). Out of the successful cases, 232 (26.9%) had informative results, and 193 (22.4%) had chromosome abnormalities. Down's syndrome was found in 110 cases. Edwards' and Patau's syndromes were found in 4 and 7 cases respectively. A case of trisomy 14 mosaic was found. There were 2 cases of trisomy 22 syndrome, one case with 46,XX/47,XX,+mar(22) and another case with 46,XX/47,XX,+r(22) karyotype. There were 39 cases of sex chromosome abnormalities, 27 of which had Turner's syndrome. Kline-felter syndrome was found in 8 patients. Triple X syndrome and true hermaphrodite (46,XX/46,XY) was each found in one case. Autosomal deletions were found in 19 patients. Autosomal duplications were found in 4 patients, and autosomal translocations were found in 10 patients. Some of these autosomal structural abnormal cases have been included in the chromosomal syndromes mentioned above.