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Unit Code 82992:
Y Chromosome Microdeletions, Molecular Detection

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Useful For

Evaluating men with azoospermia, severe oligozoospermia, or

otherwise unexplained male factor infertility

Clinical Information

Yq microdeletions involving some or all of the AZF gene are the most

frequently identified cause of spermatogenic failure in chromosomally

normal men with nonobstructive azoospermia (8.3%) or severe

oligospermia (5.5%). Among unselected infertile males, the overall

frequency of Yq microdeletions is 3%. The relative frequency of Yq

microdeletions make the evaluation for them an important aspect of the

diagnostic work up in infertile males, especially those with

spermatogenic failure (sperm density <5 million/ml).

 

Most cases of Yq microdeletions occur de novo, and due to the

consequential infertile phenotype, they are typically not transmitted.  

However, in cases where assisted reproductive technology (example:

TESE followed by ICSI) is used to achieve viable pregnancy, all male

offspring born to a microdeletion carrier will carry the deletion and may

be infertile.  

 

Men testing positive for 1 or more microdeletions who are enrolled in

an in vitro fertilization (IVF) treatment program may wish to consider

alternative options to intracytoplasmic sperm injection (e.g., donor

sperm) and consultation with an experienced reproductive

endocrinologist and medical geneticist is recommended.

 

Most Y microdeletions are the result of homologous recombination

between repeated sequence blocks.  Testing for deletions involves

investigating for the presence or absence of markers located within

non-polymorphic regions of the AZF gene.

Reference Values

Abnormal: the presence of 1 or more deletions in specific regions

of the Y chromosome (designated AZFa, AZFb, and AZFc)

Normal: the absence of deletions in the regions of the Y chromosome

under test

 An interpretative report will indicate whether or not results are consistent

with a diagnosis of Y chromosome microdeletion.

Interpretation

Y chromosomal microdeletions may be the cause of the defects in

spermatogenesis observed in some infertile men.

 

The particular markers used in this assay are expected to detect greater

than 95% of the deletions in the 3 AZF regions.(1)

Cautions

A positive result (presence of a deletion) does not necessarily mean

that this is the cause of the infertility or azoospermia in this patient.

 

A negative result (absence of microdeletions) does not

rule out the presence of other genetic or nongenetic factors that may

be the cause of infertility or azoospermia.

 

Microdeletions not detected by the markers used in this assay may be

present.

 

The absence of a deletion in DNA from peripheral blood does

not necessarily rule out the presence of a deletion in the germline DNA

(sperm).

 

The laboratory maintains quality control and quality assurance programs

to ensure a high quality of testing. Nevertheless, rare errors may occur,

for example, due to specimen mix-ups (within the laboratory or prior to

receipt by the laboratory) or due to technical errors.

 

Test results should be interpreted in the context of clinical findings,

family history, and other laboratory data. Errors in our interpretation of

results may occur if information given to us is inaccurate or incomplete.

 

A genetic consultation is recommended for all patients undergoing this

testing. Additional consultation with a reproductive endocrinologist/

urologist to discuss reproductive options is recommended when a

deletion is detected.

Special Instructions and Forms

• Informed Consent Form for DNA Testing 

Clinical Reference

1.  Simoni M, Bakker E, Eurlings MC, Matthijs G, et al: Laboratory

      guidelines for molecular diagnosis of Y-chromosomal microdeletions.

      Int J Androl 1999 Oct;22(5):292-211

 

2.  Pryor JL, Kent-First M, Muallem A, van Bergen AH, et al:  Microdeletions

      in the Y chromosome of infertile men. N Engl J Med 1997 Feb 20;336(8):

      534-539

 

3.  Kent-First MG, Kol S, Muallem A, et al: The incidence and possible

      relevance of Y-linked microdeletions in babies born after

      intracytoplasmic sperm injection and their infertile fathers. Mol Hum

      Reprod 1996 Dec;2(12):943-950

 

4.   Shalender Bhasin:  Approach  to the Infertile Man. Journ of Clin Endo

      & Metab 2007 June 92(6):1995-2004.

 

5.   Ferlin A, Arredi B, Speltra E, et al:  Molecular and Clinical

      Characterization of Y Chromosome Microdeletions in Infertile Men: A

      10-Year Experience in Italy. Journ of Clin Endo and Metab. 2007

      Mar 92(3):762-770

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