Özet:

OBJECTIVE: Hypotonia is a general term used to denote reduced tone in the limbs, trunk, or craniofacial skeletal muscles. It can be detected at birth or later in childhood. It is important to establish the diagnosis, predict the prognosis, determine treatment strategies and the risk of recurrence for later generations of the family. In addition to neurological examination and brain imaging, conventional cytogenetics, molecular cytogenetics and molecular genetic tests are important to support clinical diagnosis. Autosomal chromosome abnormalities should be considered when combined with hypotonia, minor or major malformations and cognitive impairment. A variety of chromosome abnormalities and syndromes, including clinical differences, may include atypical facial appearance, hand and foot dysmorphic findings or other organ malformations. Recent advances in genetic testing, expanding spectrum of molecular diagnostics, spinal muscular atrophy, congenital myotonic dystrophy, identification of underlying mutations (congenital muscular dystrophies and several congenital myopathies) with Prader-Willi syndrome, provide a specific diagnosis for children with this symptom. MATERIAL AND METHODS: 47 children who applied to the Trakya University Hospital, Medical Genetics Department, Genetic Diseases Diagnosis Center clinic with a pre-diagnosis of hypotonia between 2017-2019 were included in our study. Array-comparative genomic hybridization (aCGH) study was performed with patient genomic DNA. RESULTS: Copy number variations (CNV) in the size of 557kb to 40 Mb was detected in 12 of 47 patients (25.53%). The detected CNVs were researched and evaluated from the literature searches after Database of Genomic Variants (DGV), Database of genomic variation and phenotype in humans using Ensembl Resources (DECIPHER), International Standards for Cytogenomic Arrays and Public archive (ISCA) of interpretations of clinically relevant variants databases. CONCLUSIONS: Conditions that are among the causes of hypotonia in newborn and infantile periods are genetic syndromes, muscle diseases, cranial malformations, metabolic diseases, especially peroxisomal and mitochondrial diseases. In order to make a differential diagnosis among this group of diseases, invasive tests such as EMG, Cranial MR and muscle biopsy are applied. As a result, in the presence of severe hypotonia in the neonatal and infantile period, the genetic evaluation of the patient can save the patient from the burden of unnecessary invasive tests for the diagnosis of many diseases that are the cause of the unknown hypotonia. Early diagnosis is also important in terms of prevention and early treatment of problems that may arise specific to the disease. It is important to diagnose the disease in the early period, as it will allow the patient to start rehabilitation earlier.

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