Dihydropteridine reductase deficiency (DHPRD) is a genetic disorder affecting the tetrahydrobiopterin (BH4) synthesis pathway, inherited in the autosomal recessive pattern. It is one of the six known disorders causing tetrahydrobiopterin deficiency, and occurs in patients with mutations of the QDPR gene. The disease presents with such symptoms as elevated levels of phenylalanine (hyperphenylalaninemia), microcephaly, hypotonus, mental retardation and epileptic seizures. Diagnostics
Besides the traditional analysis of symptoms and investigation of phenylalanine concentrations, patients suspected for DHPRD undergo the assessment of enzymatic activity using the dried blood spot method - this permits to distinguish DHPR deficiency from the other forms of BH4 deficiency. Treatment
Patients are prescribed a phenylalanine-reduced diet, with regular monitoring of phenylalanine levels in the blood. Besides the diet, a patient may be prescribed sapropterin, a synthetic analogue of tetrahydrobiopterin. In order to restore dopamine levels in the central nervous system, patients are given L-dopa in conjunction with an inhibitor of aromatic amino acid decarboxylase that acts outside the nervous system, so as to promote the transformation of L-dopa into dopamine inside the central nervous system, and thus to improve the efficiency of the treatment. Since the insufficient levels of BH4 inhibit the transformation of tryptophan into 5-hydroxytryptophan in a reaction in which BH4 serves as a cofactor of the enzyme tryptophane hydroxylase 2, patients suffer from a lack of serotonin in their CNS. In order to correct this deficiency, they are given 5-hydroxytryptophan. In patients with DHPR deficiency, a pronounced lack of 5-methyltetrahydrofolate (5-MTHF) is observed in the central nervous system.
myoclonic seizures)
Seizures associated with fever due to illness or vaccinations
Seizures induced by prolonged exposure to warm temperatures
Seizures in response to strong lighting or certain visual patterns
Initially normal EEGs and later EEGs with slowing and severe generalized polyspikes
Normal initial development followed by slow development during the first few years of life
Some degree of hypotonia
Unstable gait and balance issues
Ankle pronation and flat feet and/or development of a crouched gait with age

Treatment
Seizures in Dravet syndrome can be difficult to manage but may be reduced by anticonvulsant medications such as clobazam, stiripentol, topiramate and valproate. Because the course of the disorder varies from individual to individual,  treatment protocols may vary. A diet high in fats and low in carbohydrates may also be beneficial, known as a ketogenic diet. Although diet adjustment can help, it does not eliminate the symptoms. Until a better form of treatment or cure is discovered, those with this disease will have myoclonic epilepsy for the rest of their lives.Certain anticonvulsant medications that are classed as sodium channel blockers are now known to make seizures worse in most Dravet patients. These medications include carbamazepine, gabapentin, lamotrigine, and phenytoin.Treatments include cognitive rehabilitation through psychomotor and speech therapy. In addition, valproate is often administered to prevent recurrence of febrile seizures and a benzodiazepine is used for long lasting seizures, but these treatments are usually insufficient.Stiripentol was the only medication for which a double-blind placebo-controlled randomized controlled trial was performed and this medication showed efficacy in trials.