Creatine‐Kinase and pyruvate‐kinase activities in normal children: Implications in duchenne muscular dystrophy carrier detection

Abstract

Serum creatine-kinase (CK) and pyruvate-kinase (PK) levels were determined in 201 boys and girls less than 15 years old to establish values and to investigate a possible correlation between enzyme activity, sex, and age. It was observed that the mean CK activity in boys was significantly higher than in females (of all ages), whereas it did not differ statistically between girls and women. A slight but significant correlation between CK activity and age was found only in females. The mean PK activity in children was significantly greater than in adult women and it decreased significantly with age in children of both sexes. Furthermore, a slight correlation between CK and PK was observed only in girls. Based on these results, we suggest that the results of CK and PK determinations of females at risk for Duchenne muscular dystrophy should be compared with controls of comparable age and sex.

Estimates of Conditional Heterozygosity Risks for Young Females in Duchenne Muscular Dystrophy

“…Our results indicate that: (a) in accord ance with the above reports, both CK and PK levels are higher among younger heter ozygotes than in adults; (b) these levels de crease steadily with age in a linear fashion, as predicted by the regression formula de rived by Lange and Zatz [1979] in relation to CK, and (c) this effect is much more evi dent among young heterozygotes than in normal children and adolescents, since the correlation coefficients obtained in our previous study of normal children were around -0.3 [Passos et al, 1985].…”

“…The subjects of this study were 338 previously re ported normal female controls with no family history of neuromuscular disease [Passos et al, 1985;Rocha, 1986;Rapaport et al, in press], 294 daughters of DMD obligate carriers and 124 obligate carriers whose data have been partially reported by Zatz et al (1976Zatz et al ( , 1978. A female was considered an obligate carrier when she had at least 2 affected sons or 1 son and another maternal affected male relative.…”

“…Some authors have suggested that the higher detection rate among young possi ble carriers than in adults might represent just an effect of ageing taking place in nor mal female controls and not related to the DMD gene [Gardner-Medwin, 1970;Bundey et al, 1979b;Thomson et al, 1979], since CK levels are higher also in normal pre-menarchal teenagers than in postmenarchal and mature women [Bundey et al, 1979a;Smith et al, 1979;Livingstone et al, 1982;Passos et al, 1985;Rocha, 1986].…”

Malignant hyperthermia—a large kindred linked to the RYR1 gene

“…It was normal in four individuals known to be M H N and the individual classified MHE ( Table 1). Six of the 1 1 individuals whose M H status was unknown were less than 15 years of age and therefore the available adult reference ranges for SCK activity were not applicable [40]. However, the two boys subsequently shown to be MHS by DNA analysis had the highest SCK activities at 234 and 344 IU.1-l respectively a t the ages of 5 and 7 years (adult reference range for the laboratory 24-190 I U k ' ) .…”