"People only see what they are prepared to see."

Ralph Waldo Emerson

This is such a truth in imaging that it should be on the frontispiece of every ultrasound-teaching program.

Of course most everyone recognized that this fetus had short limbs and abnormal mineralisation. But there is a very significant finding that only four people recognized: Mary C. Scarboro (USA), Andrea Corda (Italy), Gloria Valero (Mexico) and Adriana Soto (USA). Tthey deserve our congratulations. Before we go any further in this discussion, I will give you a last chance. Play back the video and I will tell you where to stop it. If you do not see the times on your Windows Media Player do a View > Standard (or Ctrl-1). That should open a pane below the movie with a number in the very bottom. This number looks like 00:06/01:02 which means that the movie is in the sixth second of a one minute and 2 second clip.

When ready, play back the video and stop it at second 6-11. Notice anything particular ? Now look at the segments around 27-29, 33-36, 43 seconds. I know it goes fast, but in real life scanning you do not even have the option of playing an important segment over and over again. Also I realize that the compression I use makes the image a little fuzzier than one who like, but this is a compromise for all those who have modem access and pay by the minute their Internet connections. The findings are still there bright and flashing.

This fetus was scanned at 16 weeks of gestation because of a raised maternal serum AFP. The medical history of this couple was unremarkable.

Findings

The ultrasound can revealed several structural abnormalities related to the fetal skeleton:

• There was an abnormal hypomineralization of the bones, especially at the level of the skull and the spine
• The limbs presented marked micromelia
• At the level of the elbows and knee joints bony projections or spurs were noticed
• The ribs were short, abnormally bend and showed a broad distal ending, resulting in a hypoplastic thorax.
• The hands and feet looked normal, as well as the claviculae.

The right knee:

The right elbow:

The spine hypomineralization

Most everyone detected that this fetus had short limbs and abnormal mineralisation. And of course that lead many to the diagnosis of

• Achondrogenesis,
• Osteogenesis Imperfecta type II, and
• Hypophosphatasia.

These were all good suggestions but the Mary C. Scarboro and Andrea Corda also recognized that this fetus had bony projections at the levels of the elbows and knee. The technical name for the finding is a "bone spurâ€. This is an excellent observation and a very uncommon finding. Finding a rare anomaly like that makes the diagnosis much easier. If one does a Medline search on bone spur there are 1566 articles. When the searched is narrowed to bone spur congenital the number is reduced to 49 articles. When knee or elbow is added to the keyword only zero or one article appears (and it is not relevant). If elbow spur congenital or knee spur congenital is used (dropping the bone keyword), again only one article each is found and each are easily excluded as irrelevant.

Clearly another source of differential diagnosis is needed. Doing a general internet search did not disclose anything (except of course a bunch of porno site that manage to creep in no matter what you search on !).

Another useful site for bone disorders is the International Nomenclature of Constitutional Disorders of Bone, hosted at The International Skeletal Dysplasia Registry, Cedars-Sinai Medical Center, Los Angeles, California, USA. Unfortunately, this site is not searchable, so identifying a disorder by keyword is not possible.

Another excellent source of information is the Online Mendelian Inheritance in Man database. It had been linked under the tool section but I put it more visible on the front page of The Fetus since it is so indispensable. When searching on spur only 5 conditions (out of over 10,000) are listed. I will let you investigate these but the most prominent is 241500 HYPOPHOSPHATASIA, INFANTILE.

Finally, I did not want to make too many blush, but if you had done a search in The Fetus for spur the following article would have come up:

Osteogenesis imperfecta
Diastematomyelia
DIASTEMATOMYELIA
Mesomelic dysplasia
Hypophosphatasia
xyTurner

And if you had restricted the search to spur elbow knee, then only hypophosphatasia would have appeared, and inside the reference was the following sentence:

"Diagnosis: The diagnosis should be suspected in fetus with micromelia, and demineralization of the bones. Spurs have been diagnosed postnatally that might be typical. These occur along the midshaft of long bones and at the knees and elbows". Hard to get closer than that!

Pathology

Gross pathological examination after termination of pregnancy showed very clearly the spurs at the level of the elbows and the  knees. The skull was very soft. The X-ray demonstrated the hypomineralization of the skeleton, the poor visualization of the long bones and the upper part of the spine, and the abnormally shaped and bend ribs.

The association of the hypomineralization and the presence of the bony spur at knees and elbows directed the diagnosis to spur-limbed dwarfism (Goldstein type of hypophosphatasia), an autosomal recessive disorder.

The following X-rays demonstrate the hypomineralization.

Teaching point

This case illustrates very well what Ralph Waldo Emerson said: "People only see what they are prepared to see.†If you are not aware of the existence of an anomaly it is very easy to glance over it. Hopefully, none will ever miss a bone spur again !

The other point worth making is that especially when dealing with very rare syndromes relying on what one knows may not often be sufficient. The usual process to get help is typically looking in Medline, OMIM and (hey why not ? I know it is still beginning) The Fetus. Note that no reference is ideal. As you will see the important articles that allow this diagnosis are both in a journal called "Dysmorphology and Clinical Genetics†that is not indexed in Medline.

References

More info at Hypophosphatasia

Goldstein, D. J., Nichols, W. C., Mirkin, L. D.:  Short-limbed osteochondrodysplasia with osteochondral spurs of knee and elbow joints (spur-limbed dwarfism). Dysmorph. Clin. Genet. 1: 12-16, 1987.

Shohat, M., Rimoin, D. L., Gruber, H. E., Lachman, R. S.: Perinatal lethal hypophosphatasia: clinical, radiologic and morphologic findings. Pediat. Radiol. 21: 421-427, 1991.

Spranger, J.: "Spur-limbed†dwarfism identified as hypophosphatasia. (Letter) Dysmorph. Clin. Genet. 2: 123, 1988.

Benzie R, Doran TA, Escoffery W, Gardner HA, Hoar DI, Hunter A, Malone R, Miskin M, Rudd NL Prenatal diagnosis of hypophosphatasia. Birth Defects Orig Artic Ser 1976,12(6):271-82

Terada S, Suzuki N, Ueno H, Uchide K, Kohama T: A congenital lethal form of hypophosphatasia: histologic and ultrastructural study. Acta Obstet Gynecol Scand 1996 May;75(5):502-5

Tongsong T, Sirichotiyakul S, Siriangkul S Prenatal diagnosis of congenital hypophosphatasia. J Clin Ultrasound 1995 Jan;23(1):52-5

Kleinman G, Uri M, Hull S, Keene C Perinatal ultrasound casebook. Antenatal findings in congenital hypophosphatasia. J Perinatol 1991 Sep;11(3):282-4

Wladimiroff JW, Niermeijer MF, Van der Harten JJ, Stewart PA, Versteegh FG, Blom W, Huijmans JG Early prenatal diagnosis of congenital hypophosphatasia: case report. Prenat Diagn 1985 Jan-Feb;5(1):47-52