ABSTRACT
Although trisomy of chromosome 21 is the most prevalent human genetic disorder, data from partial 21 aneuploidies are very scanty. Eight different partial aneuploidies for chromosome 21 were characterised by fluorescence quantitative PCR. Allelic dosage analysis was performed for each patient using 25 CHLC STRs covering the entire q arm. The length of the corresponding trisomies and monosomies was ascertained for five partial trisomics and three partial monosomics. All trisomic patients carried unbalanced translocations involving chromosome 21, whereas one of the monosomic patients bore a ring chromosome 21 and another showed an interstitial deletion of chromosome 21. The chromosomal breakpoints of two partial trisomy patients could be clearly delimited. However, the other three trisomies involved most of the 21 q arm as three allelic doses were detected for each marker. Although these latter patients do not show all the features of Down syndrome, genotype/phenotype correlations agree with previously reported data. The chromosomal breakpoints observed in two partially monosomic patients helped further to define the region involved in different phenotypic features associated with chromosome 21 monosomy. Telomeric material loss was also detected in a patient bearing a ring 21 chromosome. The parental origin of the aneuploidy was assigned for each case, which allowed us to conclude that two of the monosomic cases originated from de novo chromosomal rearrangements. There was no correlation with parental sex in contrast to trisomic patients originating from meiotic nondisjunction.
Subject(s)
Aneuploidy , Chromosome Aberrations/genetics , Chromosomes, Human, Pair 21 , Chromosome Deletion , Chromosome Disorders , Down Syndrome , Female , Fluorometry , Humans , Male , Microsatellite Repeats/genetics , Polymerase Chain ReactionABSTRACT
Four patients with late infantile form of Pompe's disease, acid maltase deficiency, are presented. In three of them an autosomical recessive genetical transmission was demonstrated. Signs of neuromuscular involvement were present in all of our patients before four years of age. All cases had elevated muscle and liver enzymes. Echocardiographic studies revealed a septal hypertrophy in three patients. Presence of myotonic discharges on EMG examination suggested the diagnosis in three cases. Pathological and biochemical studies of two siblings, one of them aged 14 months, without clinical findings, demonstrated that the enzyme in late infantile form of acid maltase deficiency is missing from birth. Clinical and pathological muscular involvement of case number 4, in front of normal amounts of acid maltase in this muscle, must alert clinicians to perform enzymatic studies in various tissues in order to confirm diagnosis and better understand biochemical basis of the disease.
