dopa - responsive dystonia ( drd ) is characterized by childhood - onset dystonia and a dramatic and sustained response to administration of low - doses of oral levodopa .
this disorder typically presents with gait disturbance , caused by lower limb dystonia with diurnal variation , a positive family history , and gradual progression to generalized dystonia .
a ten - year - old girl was brought with complaints of difficulty in walking and stiffness of both lower limbs , for the past six months .
she also had a history of frequent falls while walking and was unable to stand for prolonged periods .
her antenatal , birth , and neonatal periods were uneventful and developmental milestones were appropriate for her age .
her higher mental functions were normal , speech was hypophonic ; she had a gait disturbance characterized by leg stiffness , and a tendency to walk in an equinus posture , resulting in difficulty in balancing .
her tone was slightly increased in all the four limbs , with cog - wheel rigidity .
deep tendon reflexes in all the four limbs were exaggerated with extension of both great toes ( striatal toes ) .
, it was found that the symptoms and signs were relatively mild in the morning during rounds , whereas , they gradually worsened as the day progressed , rendering the child almost unable to walk by evening .
magnetic resonance imaging ( mri brain and spine were normal . in view of the typical diurnal variation of dystonia , a therapeutic challenge with levodopa / carbidopa was tried and there was a dramatic decrease in dystonia within two days and the child 's gait improved .
the child was treated with a combination of levodopa , carbidopa , and trihexyphenidyl . on follow - up
genetic studies were planned , but could not be done due to lack of resources .
drd is an inherited disorder characterized by dystonia with diurnal variation and favorable response to levodopa / carbidopa .
the inheritance is usually autosomal dominant ; however , autosomal recessive inheritance is also seen in some cases .
the enzyme deficiency responsible for the manifestations is gtp cyclohydrolase 1 ( gch ) , which is a rate - limiting enzyme in the synthesis of dopamine .
this disorder had been referred to as hereditary progressive basal ganglia disease , hereditary progressive dystonia with marked diurnal variation , segawa disease , and drd in the past . at present , segawa disease specifically denotes an autosomal dominantly inherited mutation in the gch 1 gene located on chromosome 14q22.1 to q22.2 .
the disease usually manifests in school age children , however , adults with the disease have also been reported .
initial manifestations of this disease include postural dystonia of the lower limbs with characteristic equino varus deformity of both feet .
the dystonia gets worse as the day progresses , becomes maximal by evening , and decreases after sleep by morning .
investigations characteristically reveal low levels of pteridine metabolites in the cerebrospinal fluid , normal neuroimaging , and increased blood phenylalanine levels after phenylalanine loading tests . assessing the therapeutic response to levodopa is a useful and recommended method of diagnosing drd , when the diagnosis is in doubt and when dystonia is not attributable to hypoxic ischemic encephalopathy . in one
reported series , administration of low - dose levodopa had resulted in complete to near - complete recovery of symptoms in a cohort of chinese patients , with no significant long - term side effects . in our case ,
the child presented with gait disorder characterized by dystonic movements of the lower limbs of gradual onset , which disappeared during sleep , and reappeared after getting up from bed and progressively worsened throughout the day with symptoms , for the past six months . with the above - mentioned clinical findings and a dramatic response to the levodopa / carbidopa combination
children with recent onset dystonia and gait abnormalities may pose a diagnostic challenge . a careful history and focused neurological examination , looking for diurnal variation in symptoms , holds the key in arriving at the diagnosis .
in such children a therapeutic response to levodopa might be a safe and appropriate way of confirming drd .
 children with recent onset dystonia and gait abnormalities may pose a diagnostic challenge . a ten - year - old , developmentally normal girl , presented with a six - month history of gait abnormality and dystonia . 
 her complaint worsened as the day progressed . in view of typical diurnal variation of dystonia , 
 a therapeutic challenge with levodopa / carbidopa was given and there was a dramatic response . 
 hence , a diagnosis of dopa - responsive dystonia ( drd ) was made . 
 drd is an inherited disorder characterized by dystonia with diurnal variation and favorable response to levodopa / carbidopa . 
 the inheritance is usually autosomal dominant , however , in some cases , autosomal - recessive inheritance is also seen . 