Fróðskaparrit - 01.01.1975, Page 10

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Amylo-l,6-glucosidase deficiency
also failed to support the information that these three individuals were
full sibs; it was more likely that only V. 113 and 114 were full sibs.
Incidentally, the rare Rh-gene D- -, which has formerly been described
in the population of the Faroe Islands, must be present in Y. 114, his
father and the sibs of the father in order to explain the Rh-types in this
part of the kindred.
Discussion
The relationships established between the 6 probands and
the possibility that the 7th proband was also related to the
other as well as the distribution of the patients in the larger
family give strong support to the assumption of autosomal
recessive inheritance.
The clinical picture observed in the probands brought no
new features, but the 6 probands known to belong to one
and the same family reflected the variation which may be
observed in patients carrying the same gene (in the homo-
zygous condition).
A rough estimate of the incidence of the condition may be
obtained as it is known that about 14,000 children were born
alive in the Faroe Islands during the period 1953—70, and
7 of these were later diagnosed as cases of amylo-l,6-glucosi-
dase deficiency. This leads to a higher estimate of the incidence
than found in any population studied previously. The pre-
sumed high rate of consanguinity is of course an important
factor in the explanation of this observation, but additional
possibilities should also be considered. As the prognosis of the
disease seems to be relatively good, it may be expected that a
mutant gene of this type, when introduced into a population
with high frequency of intermarriage, may give rise to a high
number of cases.
The determination of amylo-l,6-glucosidase activity in the
leucocytes seems to have provided a reliable diagnosis in all the
present probands. The definite heterozygotes show a median
value which lies between that of the patients and the normal
controls, but as the distribution of values seen in heterozygotes
overlaps the distribution in normals to a considerable extent