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Microdeletion Analysis (Other)

CPT:

88271(1), 88273(1), 88274(1) (plus appropriate tissue culture codes: 1 probe - 1 unit, 2 probes - 2 units, 3 probes - 3 units, 4 probes - 4 units, 5 probes - 5 units, 6 probes - 6 units) 88271(2), 88273(2), (for Angelman syndrome or Prader-Willi syndrome)

It is standard of care to diagnose microdeletion syndromes using fluorescence in situ hybridization (FISH).  Available microdeletion analyses include:  Angelman syndrome, cri-du-chat, DiGeorge/Velocardiofacial syndromes, Kallman syndrome, Miller-Dieker syndrome, Prader-Willi syndrome, Smith-Magenis syndrome, steroid sulfatase deficiency (X-linked ichthyosis),  Williams syndrome, Wolf-Hirschhorn syndrome.

Test Details

Use

It is standard of care to diagnose microdeletion syndromes using fluorescence in situ hybridization (FISH).

Synonyms

Microdeletion Syndrome Analysis, Fluorescence in situ Hybridization (FISH);

Methodology

Fluorescence in situ hybridization (FISH)

Pregnancy Week

0–13 Weeks
14–21 Weeks
22+ Weeks

Specimen Requirements

Specimen

Whole blood

Volume

Adult: 5-10 mL / Child: 2-5 mL  (less for newborn)

Container

Green-top (sodium heparin) tube; fixed-cell pellet or slides/coverslips of fixed metaphase cell preparations

Special Instructions

Other specimen types may be appropriate for testing. Call a laboratory genetic coordinator prior to obtaining specimens.

Causes for Rejection

Broken or dirty slides; excessive cellular debris; stains on slides

Storage Instructions

Maintain specimens at room temperature.

Additional Information

Angelman syndrome (AS) is characterized by severe developmental delay/mental retardation, absence of speech, ataxic gait, inappropriate laughter, hand-flapping and, less frequently, microcephaly and seizures. AS is not usually suspected in the first year of life, but becomes a consideration between 1-4 years of age.

Cri-du-chat is characterized by dysmorphic facial features, microcephaly, growth deficiency, intellectual disability, speech delay and a characteristic “cat-like” cry.

DiGeorge/Velocardiofacial syndromes are due to 22q11 .2 deletions. DiGeorge syndrome is a genetic disorder characterized by hypocalcemia, congenital heart defects, cleft lip and/or palate, microcephaly and mild intellectual disability. Velocardiofacial syndrome is characterized by facial abnormalities, congenital heart defects, diminished muscle tone, small stature, psychomotor disability and/or learning disabilities.

Kallmann syndrome involves the hypothalamus, causing a hormone deficiency. Symptoms include: failure to enter puberty, lack of sexual drive, infertility (non-ovulation in women and azoospermia/oligospermia in men) and no sense of smell.

Miller-Dieker syndrome is characterized by lissencephaly ("smooth brain"), mental retardation and a distinct facial appearance.

Prader-Willi syndrome (PWS) is characterized by: hypotonia, failure to thrive in infancy, rapid weight gain/obesity between 12 months and 6 years, characteristic facial features, hypogonadism and mild to moderate intellectual disability.

Smith-Magenis syndrome is characterized by flattened mid-face; down-turned mouth; hypotonia; short, broad hands; mental retardation; chronic sleep disturbance and self-injurious behavior.

Steroid sulfatase deficiency (X-linked ichthyosis) has a variable presentation characterized by dry, scaly skin, sparse hair and conical teeth in affected males.

Williams syndrome is a genetic disorder characterized by "elfin" facial features, intellectual disability, growth deficiency, hypercalcemia and cardiovascular disease.

Wolf-Hirschhorn syndrome is characterized by microcephaly, growth deficiency, intellectual disability and characteristic facial features.

Limitations

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