Identification of the sSMC in case 13 with GTG and FISH (a), MLPA (b) and SNP array analysis (c). a. GTG and FISH results: left: partial karyotype of 2 cells showing a normal chromosome 15 on the left and the sSMC on the right. Middle: partial metaphase after FISH with WCP15. Three chromosomes, both normal chromosomes 15 and the sSMC (arrow), are stained, proving the chromosome 15 origin of the sSMC. Right: Partial metaphase after FISH with probe p80, located at 15q25-qter , showing 2 signals on both ends of the sSMC (arrow) indicative for a neo(15). b. MLPA results with the kits P036B (left) and P070 (right). The probes targeting ALDH1A3 and FLJ22604 (within red circle), respectively, both located at 15qtel, are clearly elevated but below 1.6 indicating 3 copies of both genes instead of four on the sSMC. c. HumanCytoSNP-12 result. Only chromosome 15 is depicted. The upper part shows the B-allele frequency (BAF) and the lower part shows the Log2 intensity along chromosome 15. Based on BAF (absence of a BAF of 0.5 at 15q26.3 while a meiotic origin is likely due to the presence of a BAF of 0.5 in a large part of the sSMC, indicating the presence of a third haplotype) and Log2 ratio (indicating 3 copies of the most distal end of 15q), the MLPA result of a trisomy at the distal q-arm at 15q26.3, is confirmed.