This patient, though not meeting the DSM-IV TR criteria for classic RD in that her milestones were delayed to begin with and there was no deceleration in the head circumference, did show some other features suggestive of RD. The characteristic loss of purposeful hand movements, stereotypic hand washing movements with the arms flexed in front, and the ataxic gait, as in this patient, are more prevalent in RD than other autistic disorders.
3 In addition, regression in speech, communication skills and social interaction is suggestive of a pervasive developmental disorder, which, taken together with the above observations and occurrence in a female are reminiscent of RD. It has already been argued that the prevailing diagnostic criteria for RD are too restrictive, which may exclude atypical or borderline variants of this condition.
2 In addition, while autistic disorder and childhood disintegrative disorder are associated with acquired neurological disorders, the criteria and description of RD in DSM-IV TR are silent on this aspect. A recent update on diagnostic criteria for RD omitted the exclusion criterion of acquired neurological disorders in the revised criteria for variant phenotypes of this condition.
2The other pertinent facet of discussion is the use of lamotrigine in RD. Kumandas et al. used lamotrigine in two girls with RD and found that apart from convulsions, lamotrigine also improved stereotypical hand movements and autistic behaviors as happened with our patient.
4 Another study showed that lamotrigine enhanced social behavior, temper tantrums and emotional problems in some patients with RD.
5 . Besides RD, lamotrigine has been used, albeit with mixed results, in either autistic disorder or patients with intractable epilepsy showing autistic symptoms. One such open-label study showed a positive effect of lamotrigine on some autistic symptoms,
6 while a placebo-controlled trial failed to show any such effect.
7 Whether patients with RD present with motoric symptoms such as stereotypic hand movements, ataxic gait, and dystonic posturing which are differentially responsive to lamotrigine as compared to other autistic spectrum disorders, remains to be ascertained. Moreover, as lamotrigine is now known to be effective in certain affective disorders, whether RD patients with emotional dysregulation respond better to it, is worth exploring. This is suggested by decreased irritability and improved emotional stability in patients displaying autistic symptoms treated with this drug.
6 More systematic studies are needed to address these issues. At a neurotransmitter level, there is some evidence to support the role of lamotrigine in RD. Glutamate is elevated in CSF of patients with RD and lamotrigine, by way of inhibiting release of glutamate, may be effective in ameliorating some of the symptoms of this rare condition.
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