Identification of the familial sSMC in case 25: GTG and FISH (a), MLPA (b) and HumanCytoSNP-12 (c) results. a. Left. GTG partial metaphase showing the sSMC (arrow). 2nd picture: partial metaphase after FISH with the ribosomal DNA probe r521, showing one signal on the sSMC (arrow) and on the short arm of all acrocentric chromosomes. 3rd picture: partial metaphase after FISH with p190.22 (22cen) (green) and 22qtel probe (red) showing only one centromere signal and no 22qtel signal on the sSMC (arrow). Both normal chromosomes 22 are positive with 22cen as well as with 22qtel probe. Right: partial metaphase after FISH with a Cat Eye Syndrome critical region probe 102D10 showing one signal on the sSMC (arrow) and on both normal chromosomes 22. b. MLPA results with centromere kit P182 (left) en telomere kit P070 (right). The relative probe signals of the sequences targeting CECR1 and SLC25A18 in P182 and IL17R in P070 (in red circle) are clearly > 1.6 indicating 4 copies of these sequences on the sSMC. c. HumanCytoSNP-12 result. Only chromosome 22 is depicted. The upper part shows the B-allele frequency (BAF) and the lower part shows the Log R Ratio along chromosome 22. Based on the BAF (presence of a BAF of 0.5 in at least a part of the maternally inhereted sSMC, indicating the presence of a meiotic tetrasomy), the MLPA result of a partial tetrasomy 22q11, is confirmed.