N: 2.9-5.4) and elevated alkaline phosphatase (1,065 U/L; N: 200-495) levels. Renal function tests were normal (serum urea: 18 mg/dL, creatinine: 0.6 mg/dL and eGFR ≥ 75 mL/minute/ 1.73 m²) and there was no features of metabolic/renal acidosis (arterial blood gas pH: 7.4, bicarbonate: 24 mmol/L). Phosphate wasting was confirmed by reduced renal reabsorption of phosphate (TRP: 50%), and based on hypophosphatemia, increased serum alkaline phosphatase, radiological sign of rickets and a family history compatible with X-linked dominant inheritance, a diagnosis of XLH rickets was made.The child was started on oral phosphate (20 mg/Kg/day of neutral-phos powder) supplementation and calcitriol [1,25(OH) 2 D3] (0.5 μg/day). Growth hormone (rhGH) treatment was commenced after one month, with 0.03 mg/Kg/day and administered as daily subcutaneous injections. During the 12-month rhGH treatment, the patient was assessed at trimonthly intervals (at 3, 6, 9 and 12 months). Deformities were assessed clinically and by obtaining standard clinical photographs at 0 and 12 months. At rhGH onset, the height Z-score was −4.8

is just proximal to the telomere composed of highly polymorphic repetitive DNA sequences that are typically situated adjacent to gene rich areas. There are conflicting reports and wide variations ranging from 0.5% to 35% in the frequency of subtelomeric rearrangements and deletions in children with idiopathic MR.4 Present study was conducted to find its frequency in such children in a service tertiary care centre. MATERIALS AND METHODThis was a cross-sectional study done over a two-year period. The study population constituted 35 children of either sex with idiopathic MR attending paediatric outpatient department (OPD) at a tertiary care centre. Children aged 5-14 years of either sex, diagnosed as idiopathic MR were included in the study. Children < 5 years of age, children with specific dysmorphic features like Down's syndrome, children with known causes of MR like history of perinatal insult, neuro-metabolic and neuro-degenerative disorders, infections like subacute sclerosing panencephalitis (SSPE), etc. were excluded from the study.Detailed history included antenatal, perinatal, postnatal and family history to rule out any possible cause responsible for MR. Detailed examination was carried out in each child to look for dysmorphic features, neuro-cutaneous markers, anthropometry, organomegaly, neurological deficits, and malformations. Hearing assessment, ophthalmic examination, and IQ assessment was done in all the children.Investigations included magnetic resonance imaging (MRI) brain, electroencephalography (EEG), Thyroid function tests and urine for amino acids in all the children. Screening for neurometabolic, neurodegenerative disorders or chronic central nervous system (CNS) infections like SSPE was individualised and children found to be positive were excluded. Karyotyping using G banding technique 5 and multiplex ligation-dependant probe amplification (MLPA) technique, a variation of polymerase chain reaction 6 was used to detect subtelomeric abnormalities (Department of Genetics, Sir Ganga Ram Hospital, New Delhi). RESULTS Clinical FeaturesAmong the study group 35 children, 21 (60%) were males with a vast majority (42%) being in the age group of 6-8 years. Mean age was 9 ± 2.466 years.To determine the frequency of subtelomeric abnormalities in children with idiopathic mental retardation Brig KS Rana*, Col RG Holla (Retd) † ABSTRACT BACKGROUND