ONLINE REPORT High incidence of profound biotinidase deficiency detected in newborn screening blood spots in the Somalian population in Minnesota K. Sarafoglou & K. Bentler & A. Gaviglio & K. Redlinger-Grosse & C. Anderson & M. McCann & B. Bloom & D. Babovic-Vuksanovic & D. Gavrilov & S. A. Berry Received: 9 January 2009 / Submitted in revised form: 14 July 2009 / Accepted: 28 July 2009 / Published online: 7 September 2009 # SSIEM and Springer 2009 Summary Newborns identified with profound biotini- dase deficiency (BTD) by the Minnesota Newborn Screening Program (MN NBS) between 1 October 2004 and 30 May 2008 were all from new immigrant groups. Thirty-three positive cases of BTD were identified out of 264 727 infants screened by the Wolf colorimetric system during the period of this study by MN NBS. Five cases of profound BTD (0.1 to <0.6 nmol/min per ml) and 26 cases of partial BTD (0.9 to 2.3 nmol/min per ml) were later confirmed through measurement of serum biotinidase activity. The incidence of combined partial and profound BTD of 1/8540 and that of profound BTD of 1/52 945 in Minnesota are unusually high in comparison with the reported worldwide numbers of 1/61 067 for combined BTD and 1/137 401 for profound BTD. Four out of the 5 cases of profound BTD ascertained in the MN NBS cohort were of Somali ethnic background, and the remaining case was of Asian (Pakistani/Indian) ethnic background. All four Somali patients have the P497S mutation, with one of the four being homozygous for the mutation. The three compound heterozygotes all have a novel mutation (P142T) and two of them have another change (Y428Y) that has never been described. Within the last two decades, Minnesota has become home to an estimated 40 000 Somali immigrants and their children (<1% of the total Minnesota population). New population demographics prompt careful analysis of case cohorts to identify specific groups at risk for rare inborn errors of metabolism. Abbreviations BTD Biotinidase deficiency NBS newborn screening Introduction Biotinidase deficiency (BTD) is inherited in an auto- somal recessive fashion (Wolf et al. 1983) and is characterized primarily by skin and neurological abnormalities. The gene that encodes for the serum enzyme has been mapped to chromosome 3p25 (Cole et al. 1994). More than 100 mutations have been described so far (Hoffmann and Schulze 2009). No clear genotype–phenotype correlation has been shown and there are different frequencies of mutations in symptom- atic patients and patients diagnosed by newborn screen- DOI 10.1007/s10545-009-1135-7 Communicating editor: Rodney Pollitt Competing interests: None declared K. Sarafoglou (*) : K. Bentler : K. Redlinger-Grosse : S. A. Berry Department of Pediatrics, University of Minnesota, Minneapolis, MMC 8404 13-124 PWB, 516 Delaware St. SE, Minneapolis, MN 55455, USA e-mail: saraf010@umn.edu A. Gaviglio : C. Anderson : M. McCann : B. Bloom Minnesota Department of Health; Minneapolis, Minnesota, USA D. Babovic-Vuksanovic : D. Gavrilov Department of Medical Genetics, Mayo Clinic College of Medicine, Rochester, Minnesota, USA J Inherit Metab Dis (2009) 32 (Suppl 1):S –S 169 173