Spectrum of constitutional chromosomal disorders: A five-year retrospective analysis from a tertiary care center in Karachi.

Objective: Cytogenetic analysis plays a crucial role in the assessment of genetic disorders. Our study aimed to provide an overview of the prevalence of constitutional chromosomal abnormalities, enabling the recognition of common presentations and frequencies, which would assist us in identifying the disease burden and establishing better diagnostic services for cytogenetic studies. Methodology: This is a retrospective study conducted at the department of Cytogenetics, Clinical Laboratories of Indus Hospital and Health Network, Karachi, from January 2020 to May 2025. All cases, irrespective of age and gender, were included in the study. Conventional karyotyping is performed on peripheral blood using G-banding. Patients' demographics and clinical parameters were retrieved from electronic medical records of the hospital after IRB approval (IHHN-IRB NUMBER: IHHN_IRB_023_05_003). Results: Total 348 cases were received for cytogenetic analysis with suspected constitutional disorder. Median age of the patients was 10 months(one day-55years) with male to female ratio of 0.7. The most common indication was suspected Down syndrome (DS), with suspected Turner syndrome and ambiguous genitalia being among other indications. The most commonly diagnosed disorder was also Down syndrome. Conclusion: Constitutional chromosomal disorders were found to be relatively frequent in our population, with numerical abnormalities occurring more often than structural abnormalities. Trisomy 21 is the most frequent disorder found in our cohort. Overall findings highlight the diverse spectrum of constitutional chromosomal disorders in Pakistan and underscore the need to strengthen cytogenetic diagnostic services to improve early recognition and patient care.