Our patient had a very good outcome, without any sequelae. Early recognition of this syndrome to apply specific therapy as well as multiorganic failure treatment in PICU, are management key factors. HFS is probably underdiagnosed, as multiorgan failure is usually explained by other more common causes like septic shock. [4] Abbreviations APR: acute phase reactants; CJA: chronic juvenile arthritisl CNS:  Studying copy number variations using a nanofluidic platform Copy number variations (CNVs) in the human genome are conventionally detected using high-throughput scanning technologies, such as comparative genomic hybridization and high-density single nucleotide polymorphism (SNP) microarrays, or relatively low-throughput techniques, such as quantitative polymerase chain reaction (PCR). All these approaches are limited in resolution and can at best distinguish a twofold (or 50%) difference in copy number. We have developed a new technology to study copy numbers using a platform known as the digital array, a nanofluidic biochip capable of accurately quantitating genes of interest in DNA samples. We have evaluated the digital array's performance using a model system, to show that this technology is exquisitely sensitive, capable of differentiating as little as a 15% difference in gene copy number (or between 6 and 7 copies of a target gene). We have also analyzed commercial DNA samples for their CYP2D6 copy numbers and confirmed that our results were consistent with those obtained independently using conventional techniques. In a screening experiment with breast cancer and normal DNA samples, the ERBB2 gene was found to be amplified in about 35% of breast cancer samples. The use of the digital array enables accurate measurement of gene copy numbers and is of significant value in CNV studies. Variation in the human genome occurs on multiple levels, from single nucleotide polymorphisms (SNPs) to duplications or deletions of contiguous blocks of DNA sequences (1) (2) (3) (4) (5) . Copy number variation (CNV) is an important polymorphism of DNA segments across a wide range of sizes and one of the primary sources of variation in the human genome (6) . Recently, CNV has been studied extensively because of its close association with large numbers of human disorders (7, 8) . An understanding of this variation is important not only to understand the full spectrum of human genetic variation but also to assess the significance of such variation in disease-association studies. The first human CNV map was constructed from a study of 270 normal individuals with a total of 1447 CNV regions in the whole genome (9) ; more than 15 000 CNVs have been found in the human genome (http://projects. tcag.ca/variation). A recent paper demonstrated the presence of 525 novel insertion sequences across the genomes of eight unrelated individuals, which were not present in the human reference genome, and showed that many of these have different copy numbers (10) . However, the current CNV analysis is mainly dependent upon microarray-based SNP and comparative genomic hybridization (CGH) platforms, or DNA sequencing, and is therefore subject to low sensitivity and low resolution. These techniques are high throughput but lack the flexibility of analyzing individual genes or sequences of interest. Other existing technologies, such as quantitative polymerase chain reaction (PCR), are limited because of their inability to reliably distinguish less than a twofold difference in copy number of a particular gene in DNA samples (11) (12) (13) .