`Two' Quiet: Monozygotic Female Twins with Selective Mutism

Abstract

Selective mutism (SM) is a rare social anxiety disorder characterized by failure to speak in some situations despite normal verbal behavior in others. Previous work suggests a familial component for a predisposition to this disorder. The present article reviews the literature on twins with SM and examines the onset and progress of SM in a monozygotic female pair, age 5 years, 7 months. Information was gathered from parent and teacher interviews, birth records, direct observation, standard child assessment protocols and school performance reports. The variable symptom expression and severity in this concordant twin pair underline contributions from both genetic and environmental sources. Some unusual behavioral features observed in these twins, such as their popularity and non-verbal communication with classmates, underline the complexity of factors affecting the expression of SM. Pooling available data from affected monozygotic and dizygotic twins would advance understanding of the nature, course and management of this condition. K E Y W O R D S selective mutism, twinsS E L E C T I V E M U T I S M (SM) is a rare social anxiety disorder characterized by lack of speech in some situations despite normal speech in others. It is associated with exquisite sensitivity to interactions with new people in new contexts. SM typically occurs when children first enter school or another novel setting. It affects approximately 0.1% of children in the general population and 1% of children in mental health facilities (Stein, 1999). SM occurs twice as frequently in girls as in boys, and is usually evident by age three. Formal diagnosis requires that the behavior persist for one month or more, that it not reflect unfamiliarity with the spoken language and that it not be linked to developmental delay (American Psychiatric Association, 2000). Children may, however, communicate non-verbally by nodding, pointing or pushing.The crucial distinction between SM and language disorders and delays is important to appreciate. Language disorders involve inconsistent rates of development among the different components of spoken and written speech. Specific psychological processes are

Ties of silence - Family lived experience of selective mutism in identical twins

“…Their delayed speech and school performance were gradually normalized once they started to speak in public. Such delay in development is a phenomenon observed in some twins in general, not only in SM twins (Segal, 2003; Sharkey & McNicholas, 2006), but is likely to be reinforced in SM with a lack of skills training through speech.…”

“…Concordant twin cases of SM are overrepresented in some studies, but it is uncertain whether this represents a referral bias or not (Segal, 2003). SM in twins may deviate in characteristics and severity from SM in singletons and possibly contribute to reinforcement and maintenance of the muteness (Gray, Jordan, Ziegler, & Livingston, 2002; Segal, 2003; Sharkey & McNicholas, 2006). Monozygotic twins (MZ) with SM are by nature extremely rare, but interesting from a genetic point of view.…”

“…Monozygotic twins (MZ) with SM are by nature extremely rare, but interesting from a genetic point of view. Only a handful case studies are published, all involving females (McLeod & Rogers, 2009; Mora, DeVault, & Schopler, 1962; Segal, 2003; Sharkey & McNicholas, 2006; Tachibana, Nakamura, Schichiri, & Usada, 1982). Male–male twins with concordant SM are reported in a larger survey, but unfortunately without clarification of zygosity (Ford, Sladeczeck, Carlson, & Kratochwill, 1998).…”

Selektiver Mutismus bei mehrsprachigen Kindern

“…einem gehemmten Verhalten in unvertrauten Situationen und gegenüber unvertrauten Personen ausgegangen (Black & Uhde, 1995;Dummit et al, 1997;Ford et al, 1998 Unterstützung für einen genetischen Einfluss bei der Entstehung des SM findet sich bei einer doch erheblichen Anzahl schweigender Zwillingspaare (Subellok, Kresse & Bahrfeck-Wichitill, 2010). Innerhalb der internationalen Fachliteratur finden sich zahlreiche Falldarstellungen von Zwillingspaaren mit SM (Balla-Jaeger, 1971;Gray, Jordan, Ziegler & Livingston, 2002;Jaeger & Metzker, 1968;Kroppenberg, 1987;Mora, DeVault & Schopler, 1962;Segal, 2003;Sharkey & McNicholas, 2006). Betrachtet man zusätzlich größere phäno-menologische Studien zum SM finden sich in diesen Stichproben überdurchschnittlich viele Zwillinge-bei Ford et al (1998) Verhaltensrepertoire aufnehmen (Melfsen & Warnke, 2007).…”

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“…It is usually diagnosed when children enter a novel or unfamiliar setting and affects approximately 0.1% of school children, mostly female. Studies suggest a familial component underlying a pre-disposition to this disorder (Segal, 2003).…”