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Test Catalog

Test ID: FP73    
1p36.3 Microdeletion Syndrome, FISH

Useful For Suggests clinical disorders or settings where the test may be helpful

Aids in the diagnosis of 1p microdeletion syndrome, in conjunction with CMS / Chromosome Analysis, for Congenital Disorders, Blood


Detecting cryptic translocation involving 1p36.3 that are not demonstrated by conventional chromosome studies

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Chromosome 1p microdeletion syndrome is associated with a spectrum of dysmorphic features and mental retardation. The syndrome can be suspected in overweight patients with mental retardation, heart defects, and finger abnormalities. Facial features include microcephaly (small head), short neck, malformed ears, and small deep-set eyes. The phenotype is variable and depends on the size of the deletion.


FISH studies are highly specific and do not exclude other chromosome abnormalities. For this reason, we recommend that patients suspected of having 1p microdeletion syndrome also have conventional chromosome studies (CMS / Chromosome Analysis, for Congenital Disorders, Blood) performed to rule out other chromosome abnormalities or translocations.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Interpretation Provides information to assist in interpretation of the test results

Any individual with a normal signal pattern (2 signals) in each metaphase is considered negative for a deletion in the region tested by this probe.


Any patient with a FISH signal pattern indicating loss of the critical region will be reported as having a deletion of the region tested by this probe. This is consistent with a diagnosis of 1p microdeletion syndrome.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Because this FISH test is not approved by the FDA, it is important to confirm 1p microdeletion syndrome diagnoses by other established methods such as clinical history or physical evaluation.

Supportive Data

In a series of 41 patients, this FISH analysis identified a 1p36.3 deletion in 6 patients whose phenotypes were consistent with 1p microdeletion syndrome or a cytogenetic or telomere 1p deletion. Six additional patients with chromosome anomalies involving 1p, but not containing 1p36 deletion, were further characterized to define breakpoints using this probe set. This demonstrated this probe's ability to define other chromosome 1 rearrangements in this region that are not consistent with 1p-. In 29 karyotypically normal patient specimens (peripheral blood, tissue, amniotic fluid, or chorionic villus), no deletions of the region were identified.

Clinical Reference Provides recommendations for further in-depth reading of a clinical nature

1. Shapira SK, McCaskill C, Northrup H, et al: Chromosome 1p36 deletions: the clinical phenotype and molecular characterization of a common newly delineated syndrome. Am J Hum Genet 1997;61:642-650

2. Hielstedt HA, Ballif BC, Howard LA, et al: Physical map of 1p36, placement of breakpoints in monosomy 1p36, and clinical characterization of the syndrome. Am J Hum Genet 2003;72:1200-1212

3. Heilstedt HA, Ballif BC, Howard LA, et al: Population data suggests that deletions of 1p36 are a relatively common chromosome abnormality. Clin Genet 2003;64:310-316

Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test