Cytogenetics

Cytogenetics is the study of chromosomes, which carry genetic information (genes). The Cytogenetics Laboratory at Cedars-Sinai uses standard or specialized banding techniques or molecular cytogenetic techniques for the evaluation of both congenital (present at birth) and acquired chromosome abnormalities that have an impact on phenotype (clinical findings), reproduction and malignancy. The Cytogenetics Laboratory provides the full range of state-of-the-art services, including classical cytogenetic analysis, high-resolution chromosome analysis and molecular cytogenetics (fluorescence in situ hybridization, or FISH) on a variety of specimen types, such as blood, bone marrow, lymph nodes, solid tumors, tissue (e.g., POC or skin), amniotic fluid cells and chorionic villi or placenta.

Cytogenetic evaluation can be used to detect chromosome abnormalities responsible for birth defects and developmental problems. Chromosome abnormalities are observed in about four to eight percent of children with congenital malformations, as well as at least 13 percent of those with congenital heart defects. Chromosome abnormalities are also seen in patients with mental retardation and developmental delay, as well as a small proportion of children with autism. Some anomalies of sexual development can also be due to chromosomal abnormalities.

Cytogenetic analysis, primarily in children and young adults, is commonly done when a patient has:

  • Dysmorphic appearance (minor anomalies that affect appearance)
  • Mental retardation or developmental delay
  • Abnormalities of sexual development
  • Unexplained hypotonia
  • Autism or autistic spectrum disorder, especially with mental retardation or other features
  • Multiple malformations
  • Pre- or postnatal growth restriction
  • Short stature
  • Some cardiac abnormalities (e.g. conotruncal heart defects)
  • Suspected chromosomal syndrome

A significant cause of reproductive problems, cytogenetic abnormalities can be associated with a variety of issues relating to conception or giving birth. Approximately five percent of couples with recurrent miscarriage include one member with a chromosomal rearrangement. At least two percent of male infertility is associated with a chromosomal change, and 15 percent of those with azospermia can have cytogenetic abnormalities. Chromosome anomalies can be a cause of perinatal death (five percent of stillborn infants have chromosome abnormalities) and pregnancy loss (at least 60 percent of first trimester miscarriages reveal a chromosome abnormality in the fetus).

Chromosome disorders that lead to congenital abnormalities can be identified in a target population through prenatal diagnosis by amniocentesis or chorionic villi sampling (CVS). Cytogenetic analysis is commonly done for women who are pregnant or planning to become pregnant when patients have:

  • Advanced maternal age
  • Maternal blood screening consistent with positive screen for trisomy 21, trisomy 18 or neural tube defect (NTD) using biochemical markers (AFP, etc.)
  • A fetal ultrasound that indicates abnormalities including neural tube defects, cardiac anomalies, IUGR or others
  • A family history or a child with an X-linked disorder for which fetal sexing is indicated
  • A child with a chromosome abnormality or a parent who carries a balanced chromosome rearrangement
  • A child or fetus with multiple congenital anomalies where cytogenetic studies could not be performed
  • Male infertility
  • Repeated miscarriages (both male and female partners)

When cells become neoplastic, they often acquire chromosome abnormalities not seen in the normal cells of the same individual. These abnormalities can be of value in making a diagnosis, predicting prognosis and following the course of various leukemias and other cancers. The World Health Organization uses cytogenetic data as past of the criteria for classifying leukemias and lymphomas. More than 70 percent of patients with leukemia display acquired chromosome abnormalities in their leukemic cells, and between 80 and 90 percent of malignant lymph nodes will contain chromosomally abnormal cells. If the disease responds to treatment, the abnormal clone is usually lost, and only chromosomally normal cells will be detected.

Similarly, relapse or disease progression will be associated with the presence of chromosome abnormalities and increasing complexity of the abnormalities seen. Thus, cytogenetic studies can be used to monitor the course of the disease. Hematological malignancies and some solid tumors can be assessed by evaluation of appropriate cultures of peripheral blood (leukemic blood), bone marrow, lymph nodes or other tumor biopsy tissue. Standard cytogenetic analysis and FISH techniques are utilized to fully elucidate the cytogenetic diagnosis.

Common indications for cytogenetic analysis of oncology samples include:

  • Chronic (unexplained) or refractory anemia
  • Leukemia
  • Lymphoma
  • Multiple myeloma
  • Neural tumors
  • Pediatric leukemia, lymphoma or solid tumors
  • Response to chemotherapy

For information or to request a sample pickup, call (310) 423-4987.

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