rickets is still a common health problem and is considered to be a challenge even in developed countries . epidemiological data are not available in many countries , etiology is sometimes difficult to establish and vitamin d supplementation and rickets treatment have been debated for a long time . a child aged 10 months old was admitted in pediatric emergency department with focal seizures with secondary generalization . the child has , delay in motor developmental mile stones and hypotonia and poor gain in height . biochemical and radiologic signs were suggestive for rickets . biochemical profile showing low serum calcium-6.1 mg / dl ( 9.2 - 11 mg / dl ) , low phosphorus-3.9 mg / dl ( 3.4 - 6.2 mg / dl ) , elevated alkaline phosphatase-4116 u / l ( < 269 u / l ) parathyroid hormone was 233.6 pg / ml ( 15 - 65 pg / ml ) 25-oh vitamin d was 40 ng / dl . radiographic images of the wrist showed fraying and cupping of the distal radius and ulna , as well as bone demineralization ; the metaphyses are widened , irregular and cupped . physical examination , biochemical data ( hypocalcemia , mild hypo - phosphatemia , high serum concentration of alkaline phosphatase ) and rachitic changes on x - ray , were compatible with the diagnosis of rickets . the child was started on sodium valproate 20 mg / kg / day , calcium 500 mg / day and vitamin d 6 lakh iu following which there was no improvement in the serum calcium level and there was recurrence of seizures . then endocrinologist opinion sought following which the child was initiated on 0.5 g / day of active vitamin d (  cacidiol ) along with 1000 mg of calcium . there was no seizure recurrence in the last 15 months and serum calcium normalized . in view of response to 1  calciferol 1,25 oh vitamin d and enzyme studies were not done in view of financial constraints and lack of availability . a total of 10 different allelic variants of vddr have been identified , exhibiting little or no clinical differences . prominent clinical manifestations of vddr - i include growth failure , short stature , skeletal abnormalities , genu valgum , rachitic rosary , open fontanels , pathologic fractures , muscle weakness and convulsions . radiologic findings usually include fractures , generalized osteopenia , growth failure and arched or curved legs . the most common laboratory findings include hypocalcemia , hypophosphatemia , elevated parathormone levels and high alkaline phosphatase . moreover , the serum levels of 25(oh ) vitamin d are normal or raised while the levels of 1,25(oh ) vitamin d are low or undetectable . vitamin d is intimately involved in a wide variety of biologic processes , including calcium homeostasis , bone formation and cellular differentiation . in order to exert its effects , vitamin d must be activated by a metabolic pathway that requires the enzymatic activity of 25-hydroxylase and 1--hydroxylase . the gene for vddri has been recently mapped to the long arm of chromosome 12 , region one bands 2 - 4 ( 12q12-q14 ) , representing the location of the 1--hydroxylase gene . hence , it has been suggested that the disease should be referred to as 1--hydroxylase deficiency . stong clinical suspicion is required for the clinical diagnosis of vddr and therapeutic challenge with 1  calciferol will prove the diagnosis .