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Skip Navigation LinksHome Page    >    Tests during the pregnancy    >    Failure to Demonstrate the Fifth Middle Phalanx
 
 
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Failure to demonstrate the fifth middle phalanx (late calcification of the middle phalanx of the fifth finger)

Types and clinical signs

Each of the fingers apart from the thumb has 3 sections, called phalanges. Sometimes ultrasound examination of the fifth finger fails to demonstrate the middle phalanx - this is a result of delayed ossification, i.e. delay in the deposition of calcium in the bone of the middle phalanx. This does not constitute a defect, and it will always develop into a normal fifth finger.

In some cases the middle phalanx can be seen, but appears to be smaller than usual. This condition manifests as a slight inward curvature of the little finger - this is called clinodactyly and is of no clinical importance. Clinodactyly can be hereditary and be present in one of the parents. In another group of cases, the bone is completely normal.

The delayed ossification of the phalanx in this digit has no clinical significance and no adverse effects. It constitutes an ultrasonographic sign that may slightly raise the statistical risk for Down syndrome, although this is under dispute. This correlation is considered less statistically significant nowadays. The exact degree of increased risk for Down syndrome, if any, is not precisely known but is estimated to be up to approximately 3 times.

The finding in the fifth finger as part of an aggregate of parameters estimating the statistical risk for chromosome disorders

There are several parameters that establish the statistical probability for Down syndrome, and the presence of delayed ossification of the phalanx in this digit can be considered as part of the aggregate of these parameters. Normal nuchal translucency, young maternal age, absence of other signs or defects on ultrasonography, and a normal biochemical screening result are all factors that indicate a significantly reduced risk for Down syndrome.

What should be done once this is diagnosed?

Opinions vary.
Amniocentesis (or chorionic villus sampling) is undoubtedly the only test that can categorically rule out chromosome disorders.

However, it is neither medically indicated nor recommended that every pregnant woman should undergo amniocentesis - only those who are at high risk of having a specific problem that can be examined by this test (see information sheet titled: Why is there no medical recommendation for amniocentesis in all cases?).

Most opinions hold that in the great majority of the cases in which middle fifth phalanx ossification delay is the sole finding, and taking into account the other parameters mentioned above, which do not raise the risk for a chromosome disorder, the weighted risk is not in the high-risk range for which amniocentesis is indicated.

For practical purposes

The -gold-standard- threshold for recommendation of amniocentesis is a risk of Down syndrome greater than 1:386 based on the results of the biochemical marker screening tests, and when the weighted risk is equal to or higher than this amniocentesis is generally recommended. However, the presence of middle fifth phalanx ossification delay in the fetus may statistically increase the risk of Down syndrome. Therefore in these cases some physicians suggest that this should be integrated with the results of the biochemical screening tests and the new threshold for recommending amniocentesis is a risk for Down syndrome of greater than 1:1000 in the biochemical marker screening tests. If other abnormal findings are also present, these guidelines are insufficiently established and the woman should be referred for genetic counseling. In genetic counseling, the necessity for amniocentesis can be assessed.

Inheritance pattern

Not yet known - this will be ascertained in the future.

Clindodactyly is transmitted by autosomal recessive inheritance.

Penetrance

Not known

Associated features that can be demonstrated in tests performed during pregnancy

It is important to look for other ultrasonic signs associated with Down syndrome and other chromosomal syndromes.

It is also important to refer the couple for genetic counseling within which the significance of the finding and the advisability of undergoing amniocentesis will be discussed. All data, including the results of other tests performed during the pregnancy such as alpha-fetoprotein, nuchal translucency, etc., should be brought to this counseling.

What is the risk of recurrence in a subsequent pregnancy?

Not known

Molecular genetic information

The gene for the disease

Not known

Location

Not known

Genetic testing

Diagnostic testing

Not available

Carrier testing

Not available

Fetal testing

Ultrasound examination only
 
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