We collected data on growth, psychomotor development, speech and language development, and intellectual function on a cohort of 100 males with the fragile X chromosome and 95 carrier females. The data include information on prenatal growth (33 males), growth during the preadult years (32 males), psychomotor development during the first 2 years (25 males), speech and language development (15 males and 5 females), and intellectual function (93 males, 33 females, and 10 obligate carriers who were cytogenetically normal). Birth measurements appeared normal when plotted on the Usher/McLean curves of newborn infants (mean head circumference - OFC - at 40th centile, length at 60th centile and weight at 55th centile). Following birth, OFC rose above the 50th percentile and continued above average throughout the preadult years, whereas average length was above average for the first 5 years only and weight did not deviate from the normal mean. Psychomotor development lagged behind the norm from birth with affected males requiring nearly twice as long as expected to sit alone, walk unassisted, and say first words clearly. All males and females studied had significant language delay; all except one male had abnormalities of articulation. All on whom a clear voice sample was obtained had low voice pitch, and 80% had a hoarse or harsh quality of voice. Five males had word repetitions or perseverative speech during the preadult years. The mean IQ of the 93 males studied was 33 and regression analysis demonstrated a decrease in intellectual performance with age. Four fifths of the female carriers who expressed the fra(X) had intellectual performance in the mentally retarded range and showed similar decrease in performance with age. Obligate female carriers who did not express the fra(X) site had normal IQs (IQ 102 +/- 13.3).

Adolescent↗

PubMedDate not supplied

Relationship between age and IQ among fragile X males: a multicenter study.

Longitudinal decline in IQ among fragile X males was reported recently. However, there are problems in retesting IQ that may affect scores. Two such factors are intertest time interval and score obtained on the first test. To determine the generality of IQ score changes, we examined 101 fragile X males from 6 centers. To ensure high test-retest reliability, only results from Stanford-Binet and Wechsler tests were used. Thus there were retest scores from 60 subjects. Test-retest reliability between first and last scores was very good (r = 0.85) and comparable to those seen in nonfragile X mentally retarded individuals. Also computed were z-scores of differences in IQ scores. The z-score differences were distributed about a mean at 1 SD below the expected zero value. Eighteen subjects showed statistically significant decreases in IQ, 6 showed statistically significant increases, while 5 showed the same scores. Z-score differences were not correlated with type of residence or elapsed intertest interval, but were negatively correlated with first score obtained, indicating a regression-to-the-mean effect. Using a multiple regression analysis, we found first score obtained, age tested, and age retested significant predictors of score differences, accounting for 19% of the total variance. These results suggest that factors previously identified as affecting retest scores have a smaller effect than originally thought. It is suspected that decline in IQ is associated with dynamic neurological processes and needs to be investigated further.

Adolescent↗