DEAF-MUTISM IN CHILDREN
WITH SPECIAL REFERENCE TO THE CONGENITAL TYPE AFTER MATERNAL RUBELLA
ELLlS FAssER, M.B., CH.B., D.C.H.
Pretoria
General Survey. Deaf-mutism results from congenital
deafness, or complete loss of hearing before the age of
seven years. The dumbness is secondary to defective
hearing and in most congenital cases, the organ of Corti
is undeveloped. (Otosclerosis occurs later in life, and the
auditory nerve is intact) Congenital deaf-mutism may
actually be •acquired' in utero (e.g. as in syphilis,
rubella), so all congenital deaf-mutism is not necessarily
hereditary in origin. As many deaf-mutes are educated
in special schools, they often meet and marry deaf
partners. From a eugenic point of view this may be better
than marrying into normal families and so spreading the
affliction, when the latter is of genetic origin.
Deaf-mutes occasionally exhibit retinitis pigmentosa, and
more often feeble-mindedness and sterility. Hypogenitalism and infantilism are sometimes found in recessive types. One family is quoted by Gates (1946), where
deaf-mutism is combined with heterochromia iridis,
Horner's syndrome and strabismus.
Otitis media may cause deafness, and according to
Bauer (1945) susceptibility to otitis media may be
inherited, being sometimes familial. The deafness, if it
occurs early, may be associated with mutism.
Gates (1946) also cites Lindborg, who believes that
hereditary deaf-mutism is due to one Mendelian recessive
character, and not to Plates' two factors. Love (1920)
described a family with five affected generations,
descended from a common ancestor, and postulates a
recessive mode of inheritance.
Kraatz (1925) studied many pedigrees statistically, and
came to the conclusion that deaf-mutism cannot be due to
a single dominant, recessive or sex-linked character, but
that the statistics pointed to the operation of two recessive
factors. However, on the basis of two factors, Deaf x
Deaf may give all normal children in ome familie , so
that lack of penetrance is a more probable explanation.
Persons who are heterozygous for • deafness' can hear
perfectly well on the audiometer, so the condition is
recessive.
Tinkle (1933) also believes that two recessive genes are
concerned with the production of hereditary deaf-mutism,
but suggests that a third pair of genes control the development of the middle and internal ears.
Switzerland has the highest incidence of deaf-mutism in
the world, namely 0.12% as against 0.023%, in Germany
for instance (Gates, 1946). Hanhart is cited as saying that
60% of deafness in Switzerland is 'sporadic', being
related to cretinism. In Sweden, where there are few
cretins, the ratio of congenital to acquired deafness is
estimated at 100: 67. Murray and Wilson (1945) show that
there is a relationship between deaf-mutism and goitre and
cretinism. In three goitrous districts in Oxfordshire with
low water and soil iodine content, there were 28 deafmutes in a population of 36,635, whereas in three nongoitrous areas there were only five deaf-mutes in 38,910.
Some of the deaf-mutes have enlarged thyroids, and belong
to goitrous families, but both sexes are equally affected,
which does not obtain in goitre.
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