Minimal Phenotypic Findings of Down Syndrome in a Patient with True Trisomy 21

Abstract

We present a 23-year-old Iranian male, who was born full-term by normal vaginal delivery to a 27-year-old, G1, P0 mother. His birth weight was 2.5 kg. The birth height and head circumference are not available. The gestational and neonatal periods were uneventful. Developmental milestones were delayed. He could sit without support at age two years, walked at age 4 years, and talked in sentences at age 7 years. Despite apparent developmental delay, no diagnostic work-ups were performed. Reportedly, he attended regular school up to the 7th grade. He has not been able to hold a job steadily. He came to our attention while a pedigree was prepared for his sister who came to our clinic for a routine pre-marital genetic counseling, and he was then evaluated due to his history of “learning disability.”

On physical examination, his weight was 58 kg, his height was 150 cm, and his head circumference was 54.5 cm. He is communicative. He can read and write well. His IQ is 65-70. He has a stooped posture, and minor dysmorphic features, such as mild epicanthic folds, slightly downslanting palpebral fissures (not upslanting). prominent nose with slightly elongated nasal septum, narrow palate, and fine motor incoordination. The rest of the physical examination including the heart auscultation and dermatoglyphics were normal. No dysmorphic genetic syndrome was suspected. A chromosome analysis was performed because of the history of developmental delay, which revealed 47, XY.+21. Repeat chromosome analysis and FISH using the whole chromosome 21 paint and distal Q21 probe showed straightforward trisomy 21, i.e., all three chromosomes 21 painted over entire length, and no regions of chromosomes 21 were translocated elsewhere in the genome. Patients with the features of Down syndrome and relatively good performance are likely to have mosaicism, which is not always easy to demonstrate. Therefore, the possibility of mosaicism in this patient exist. An attempt for fibroblasts culture from a skin biopsy sample was unsuccessful. He has recently married. Reportedly, he has difficulties in his sexual performance.