Some Genetic Considerations in Cystic Fibrosis. A Study of Nail and Sweat Sodium in Two Sibships1

Abstract

Summary The rationale for studying tissue that stores sodium as it occurs in nails is presented. The results of our studies on the concentration of sodium in 242 patients with C.F., 63 healthy children, 171 parents of children with C.F., 51 healthy adults and 184 siblings of patients with cystic fibrosis are presented. The elevated nail sodium concentration was detected in over 95 % of the patients with C.F. and in no patient with C.F. was the value less than 80 mEq/Kg. Seven out of 8 children born to parents, one of whom had C.F., showed elevated nail sodium. By definition these healthy children are the only presently recognized heterozygotes in infancy. The sibling group showed a wide range of values suggesting the possibility of indicating the heterozygote. The nail and sweat sodium results in three generations of two selected sibships is shown in graphic form. Variations are noted which indicate that this type of study does not select the heterozygote for the gene of cystic fibrosis. The usefulness of the measurement of nail sodium is stated. It is hoped that this report will stimulate others to seek other methods for detecting the heterozygote.

Sodium, Calcium, and Magnesium Levels in Nails of Children with Cystic Fibrosis of the Pancreas

“…A better separation was achieved when all three values were combined. Discussion The present study confirms the finding of a raised mean sodium level in the nails of children with fibrocystic disease of the pancreas but with some overlap with the normal range as described previously (Kopito et al, 1965;Shwachman and Kopito, 1967;Bock et al, 1967). An additional finding is the raised levels of both calcium and magnesium, which does not appear to have been noted previously.…”

“…To date there appears to be no simple test which is useful in detecting the heterozygote. Sweat or parotid sodium levels which are useful in detecting the homozygote appear to be of little use in identifying the heterozygote Shwachman and Kopito, 1967). The results of the present study show the advantage of measuring nail sodium, calcium, and magnesium levels over nail sodium levels on their own in detection of the homozygote.…”

“…It has been suggested that as many as 1 person in 16 may carry the gene for CF of the pancreas (Shwachman and Kopito, 1967). Detection of the heterozygote is therefore desirable.…”

“…Sweat sodium levels are raised in CF of the pancreas and this measurement has been used extensively as a means of detection (Gibson and Cooke, 1959;Goldbloom and Sekelj, 1963;Warwick, 1966;Friedlander, Gasber, and Lieb, 1969). Raised levels of sodium were found in the nails of children with CF of the pancreas by Kopito et al (1965), Shwachman and Kopito (1967), and Bock et al (1967. Due to overlap in the levels found in CF children with those in healthy children, the usefulness of the nail test is confined almost exclusively to cases with clinical features of the disease and borderline sweat sodium levels.…”