Prader-Willi syndrome (PWS) is a multisystemic disorder caused by the loss of expression of paternally transcribed genes within chromosome 15q11-q13. Most cases are due to paternal deletion of this region; the remaining cases result from maternal uniparental disomy (UPD) and imprinting defects. To better understand the phenotypic variability of PWS, a genotype-phenotype correlation study was performed in 91 children with PWS. Patients were diagnosed by Southern Blot Methylation assay and genetic subtypes were established using FISH and microsatellite analyses. Fifty-nine subjects with deletion (31/28 males/females; mean age 3.86 years), 30 with UPD (14/16 males/females; mean age 3.89 years) and 2 girls with a presumed imprinting defect (mean age 0.43 yrs) were identified. For correlation purposes patients were grouped as "deleted" and "non-deleted." An increased maternal age was found in the UPD group. Four of Holm's criteria were more frequently present in the deleted group: need for special feeding techniques, sleep disturbance, hypopigmentation, and speech articulation defects. Concerning cognitive assessments, only 9.52% of subjects with deletion had Full-Scale IQ (FSIQ) > or =70, while 61.53% of subjects without deletion had FSIQ > or =70. Similar results were found in behavioral measures. Sleep disorders and carbohydrate metabolism were systematically assessed. Polysomnoghaphic studies revealed a higher frequency of central events with desaturations > or =10% in the deleted group (P = 0.020). In summary, the phenotype was significantly different between both groups in certain parameters related to the CNS. These results might be related to the differences in brain gene expression of the genetic subtypes.

Leigh syndrome (LS) is a mitochondrial progressive encephalopathy characterized by bilateral symmetric necrotic lesions of the central nervous system. Maternally inherited Leigh Syndrome (MILS) represents $10-20% of LS. Mutations in MT-ATP6 are the most common, being m.8993T > C/G the classical mutations. Molecular diagnosis for mitochondrial diseases is always a challenge and Multiplex ligationdependent probe amplification (MLPA) of mitochondrial DNA can be an initial test for molecular diagnosis, although it is not widely used. We present a MILS patient in which MLPA was able to detect the common m.8993 T > G mutation and serve as a first approach for the definite molecular diagnosis. ARTICLE HISTORY

Background: Pediatric patients with steroid-resistant nephrotic syndrome (SRNS) and focal segmental glomerulosclerosis (FSGS) may relapse and current second line agents include mycophenolate mofetil. However, there is no current information about the use of the sodium salt of mycophenolic acid (SMPA) in this population. Objectives: We conducted a prospective study on the efficacy and pharmacokinetics of SMPA in children with FSGS. Patients and Methods: Patients without NPHS2 pathogenic variants received SMPA at dosages between 460 to 720 mg/m2/d for 12 months after previous treatments failure. Clinical and biochemical assessments were performed. Blood samples were obtained after the first dose and at steady state (3 months after the onset of treatment) and total and free mycophenolic acid (MPA) was quantitated using HPLC-UV. Results: Two patients showed partial remission after the 12-month period of SMPA treatment with a notable decrease in proteinuria and an increase in serum albumin levels. Maximum MPA concentrations after the first dose and at steady state were 11.6 µg/mL and 10.5 µg/mL, respectively, without drug accumulation. Maximum MPA free levels after the first dose and at steady state were 192.9 and 120.6 ng/mL, respectively. MPA levels became undetectable after 4 hours of the administration in all cases. Conclusions: SMPA is a promising agent for pediatric patients with SRNS and FSGS but SMPA schedule of treatment should be revised with shorter intervals of administration and higher doses than those used in the present study in order to attain higher systemic exposures and accumulation of the immunosuppressant drug. Further efficacy and pharmacokinetic studies should be performed to confirm these findings.

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