Interpreting the karyotype Lab technicians compile karyotypes and then use a spe

Question

Interpreting the karyotype

Lab technicians compile karyotypes and then use a specific notation to characterize the karyotype. This notation includes the total number of chromosomes, the sex chromosomes, and any extra or missing autosomal chromosomes. For example, 47, XY, +18 indicates that the patient has 47 chromosomes, is a male, and has an extra autosomal chromosome 18. 46, XX is a female with a normal number of chromosomes. 47, XXY is a patient with an extra sex chromosome.

A 1. What notation would you use to characterize Patient A's karyotype?

Making a diagnosis

The next step is to either diagnose or rule out a chromosomal abnormality. In a patient with a normal number of chromosomes, each pair will have only two chromosomes. Having an extra or missing chromosome usually renders a fetus inviable. In cases where the fetus makes it to term, there are unique clinical features depending on which chromosome is affected. Listed below are some syndromes caused by an abnormal number of chromosomes.

A 2. What diagnosis would you give patient A?

Diagnosis Chromosomal Abnormality Normal # of chromosomes patient's problems are due to something other than an abnormal number of chromosomes. Klinefelter's Syndrome one or more extra sex chromosomes (i.e., XXY) Down's Syndrome Trisomy 21, extra chromosome 21 Trisomy 13 Syndrome extra chromosome 13

Explanation / Answer

QA1). 44 + XXY

QA2).

1. Hormone testing: Blood or urine samples can reveal abnormal hormone levels that are a sign of Klinefelter syndrome.

2. Chromosome analysis: Also called karyotype analysis, this test is used to confirm a diagnosis of Klinefelter syndrome.

Klinefelter's Syndrome

44 + XXY

one or more extra sex chromosomes (i.e., XXY)

Down's Syndrome

(44 +1) XX or (44 +1) XY

Trisomy 21, extra chromosome 21

Trisomy 13 Syndrome

(44 +1) XX or (44 +1) XY

extra chromosome 13

The diagnostic procedures available for prenatal diagnosis of Down syndrome are chorionic villus sampling (CVS) and amniocentesis

Klinefelter's Syndrome

44 + XXY

one or more extra sex chromosomes (i.e., XXY)

Down's Syndrome

(44 +1) XX or (44 +1) XY

Trisomy 21, extra chromosome 21

Trisomy 13 Syndrome

(44 +1) XX or (44 +1) XY

extra chromosome 13

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