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Microtia-anotia (M-A) can occur either as an isolated defect or in
association with other defects. Only in a minority of cases has a
genetic or environmental cause been found; in these cases, M-A is
usually part of a specific pattern of multiple congenital anomalies.
For instance, M-A is an essential component of isotretinoin
embryopathy (243440),
is an important manifestation of thalidomide embryopathy, and can be
part of the prenatal alcohol syndrome and maternal diabetes
embryopathy. M-A occurs with a number of single gene disorders, such
as Treacher Collins syndrome (154500),
or chromosomal syndromes, such as trisomy 18. M-A also occurs as part
of seemingly nonrandom patterns of multiple defects, such as
Goldenhar syndrome (164210).
Mastroiacovo et al. (1995) studied the
epidemiology and genetics of microtia-anotia (M-A) using data
collected from the Italian Multicenter Birth Defects Registry (IPIMC)
from 1983 to 1992. Among 1,173,794 births, they identified 172 with
M-A, a rate of 1.46/10,000; 38 of the 172 infants (22.1%) had anotia.
Of the 172 infants, 114 (66.2%) had an isolated defect, 48 (27.9%)
were multimalformed infants (MMI) with M-A, and 10 (5.8%) had a well
defined syndrome. The frequency of bilateral defects among
nonsyndromic cases was 12% compared to 50% of syndromic cases. Among
the MMI, only holoprosencephaly was preferentially associated with
M-A; 4 cases were observed versus 0.7 expected (p = 0.005). No
geographic variation in the prevalence of nonsyndromic cases was
observed nor was there evidence of time trends. Mothers with parity 1
had a higher risk of giving birth to an MMI with M-A. Mothers with
insulin-dependent diabetes were at significantly higher risk for
having a child with M-A. Mastroiacovo et al.
(1995) suggested autosomal dominant inheritance with variable
expression and incomplete penetrance 'in a proportion of cases,' or
multifactorial etiology. Three cases had consanguineous parents, but
there were no other affected sibs to support recessive inheritance.
Gupta and Patton (1995) described a
large kindred with autosomal dominant inheritance of congenital
microtia and auditory meatal atresia with conductive deafness. Five
generations were affected. One of the affected members had renal
cysts, suggesting that this is a variant of the branchiootorenal
(BOR) syndrome (113650).
However, Gupta and Patton (1995) maintained
that congenital microtia/anotia is a distinct entity. They found
previous reports of 9 families of which autosomal recessive
inheritance was implied in 4 and autosomal dominant inheritance in 5.
Guizar-Vazquez et al. (1978) described a
mother with microtia and meatal atresia on the right, whose son had
the same combination on the left. Both had some macrostomia and
facial asymmetry, but features of Goldenhar syndrome (164210)
and Treacher Collins syndrome (154500)
were missing. Zankl and Zang (1979)
supported irregular dominant (presumably autosomal) inheritance on
the basis of a family with 5 affected members in 4 sibships of 2
generations. Orstavik et al. (1990)
described right-sided external ear malformations and conductive
hearing loss in a grandfather, his daughter, and granddaughter. The
grandfather and granddaughter had microtia and meatal atresia,
whereas the daughter had a normal outer ear except for a narrow
meatus and auricular appendages. Sanchez-Corona
et al. (1982) and Oliveira et al.
(1989) also described presumed autosomal dominant inheritance.
Victor A. McKusick : 8/18/1995
terry : 3/26/1996
mark : 1/17/1996
terry : 1/11/1996
mimadm : 11/3/1995
mark : 8/18/1995