Pentasomy X Syndrome in Neonate: A Rare Disorder

Abstract

Pentasomy X is a rare syndrome with variable phenotype, that affects females with characteristic clinical features such as severe mental retardation with delayed speech, short stature, facial dimorphism, osseous, articular/skeletal/limb abnormalities, and congenital heart defects. Clinical course of the disease seems to be adverse as there has been no evidence of life till adulthood. This case study was of one-month-old girl referred for cytogenetic evaluation that revealed 49,XXXXX karyotype, indicating Pentasomy X syndrome. Studies have mentioned meiotic successive nondisjunction errors in maternal meiosis or combined maternal and paternal origin as a mechanism for Pentasomy X formation which has been supported by genotyping studies using Short Tandem Repeats (STR) X-linked polymorphic markers. An early restricted fetal growth and movements along with increased nuchal fold in pregnancy could suggest referral to prenatal karyotyping studies. Prenatal diagnosis of Pentasomy X syndrome is a challenge due to absence of advanced maternal age and maternal screening markers along with subtle nonspecific Ultrasonography (USG) abnormalities that are detected late in the pregnancy. Hence, there is a strong need of Non Invasive Prenatal Screening (NIPS) with clinical coverage of sex chromosomes in routine pregnancy management along with 3D high resolution USG evaluation as a mandatory workup to rule out Pentasomy X irrespective of advanced maternal age. Management frame work through genetic counseling help patients to adapt to the challenging diagnosis and early interventions for patient management.

Keywords

• chromosomal analysis
• dysmorphism
• non-disjunction
• prenatal diagnosis
• short tandem repeats markers