tl_files/tiny_templates/Bilder TL/sSMC/kl-sSMC.jpg


Here some layman explanations on this page can be found

We provide 25 different languages --> English below  tl_files/tiny_templates/Bilder TL/Flags/01-UK.jpg


The group of Dr. Liehr in Jena, Germany presently characterizes (on request) sSMC from all over the world (

We already characterized sSMC of carriers native from Armenia, Austria, Australia, Belarus, Belgium, Brasil, Canada, China, Croatia, Cyprus, Egypt, Equador, Denmark, France, Greece, Great Britain, Hungary, India, Israel, Italy, Jordan, Korea, Lebanon, Montenegro, Morocco, New Zealand, Poland, Portugal, Romania, Russian Federation, Saudi Arabia, Spain, Sri Lanka, Switzerland, Serbia, Slovakia, Slovenia, South-Africa, Taiwan, Tunisia, Turkey, Ukraine, Uruguay or USA. The corresponding countries are labelled in red in the 'globe' below.

tl_files/tiny_templates/Bilder TL/Flags/0-world.jpg



tl_files/tiny_templates/Bilder TL/Flags/02-arab.jpg Arab/ Egypt tl_files/tiny_templates/Bilder TL/Flags/03-Armenia.jpg Armenian tl_files/tiny_templates/Bilder TL/Flags/04-china.jpg Chinese
tl_files/tiny_templates/Bilder TL/Flags/05-croatia.jpg Croatian tl_files/tiny_templates/Bilder TL/Flags/06-Czech.jpg Czech tl_files/tiny_templates/Bilder TL/Flags/07-Denmark.jpg Danish
tl_files/tiny_templates/Bilder TL/Flags/08-dutch.jpg Dutch tl_files/tiny_templates/Bilder TL/Flags/09-Finn.jpg Finnish tl_files/tiny_templates/Bilder TL/Flags/10-frensh.jpg French
tl_files/tiny_templates/Bilder TL/Flags/11-german.jpg German tl_files/tiny_templates/Bilder TL/Flags/12-Greece.jpg Greek tl_files/tiny_templates/Bilder TL/Flags/13-Isreal.jpg Hebrew
tl_files/tiny_templates/Bilder TL/Flags/14-Hungary.jpg Hungarian tl_files/tiny_templates/Bilder TL/Flags/15-India.jpg Indian tl_files/tiny_templates/Bilder TL/Flags/16-Italy.jpg Italian
tl_files/tiny_templates/Bilder TL/Flags/17-Japan.jpg Japanese tl_files/tiny_templates/Bilder TL/Flags/18-Poland.jpg Polish tl_files/tiny_templates/Bilder TL/Flags/19-Portugal.jpg Portuguese
tl_files/tiny_templates/Bilder TL/Flags/20-Russia.jpg Russian tl_files/tiny_templates/Bilder TL/Flags/21-Serbia.jpg Serbian tl_files/tiny_templates/Bilder TL/Flags/22-Slov.jpg Slovak
tl_files/tiny_templates/Bilder TL/Flags/22-spain.jpg Spanish tl_files/tiny_templates/Bilder TL/Flags/23-Sweden.jpg Swedish tl_files/tiny_templates/Bilder TL/Flags/24-Turkey.jpg Turkish


Click here for specific patient-information
as provided by the patient supportgroup 'Unique'



Small supernumerary marker chromosomes (sSMC)


The constitutional karyotype of human consists of 46 chromosomes (46,XX or 46,XY).
Each chromosome is present twice, apart from the X- and Y-chromosome in male.
In summary there are 24 different human chromosomes (1-22 and X and Y). See Fig. 1.

However, about 3 million individuals of the whole human population (7 billion) do not have 46 but 47 chromosomes,
i.e. 46 normal chromosomes and one small supernumerary marker chromosome (47,XX,+mar or 47,XY,+mar).

These small supernumerary marker chromosomes (= sSMC) can originate from
each of the 24 human chromosomes and have different shapes. See Fig. 2.

About 70% of the cases with sSMC are de novo, 30% are inherited within a family.
About 30% of the carriers of a sSMC are clinically abnormal, 70% are clinically normal.
Thus, the name 'patient with a sSMC' summarizes a very heterogeneous group of persons/patients .

The main problem in connection with sSMC appears, when the diagnosis of the sSMC presence is made prenatally.
Up to now there has not been a possibility to make clear predictions about the outcome of the pregnancy. See Fig. 3.

Presently, research is going on towards a genotype-phenotype correlation of sSMC.
This page collects all published cases with an sSMC to come nearer to this goal.

As shown below in Fig. 4 on the example of chromosome 2: there are hints that it is possible in principle (!)*** to distinguish benign from malignant sSMC.

*** The whole story is not as simple as it is shown in this diagram for chromosome 2 as additional factors like uniparental disomy (UPD) or additional complex or cryptic rearrangements are possible, which may influence clinical outcome.

At present, we are setting up a collection of sSMC cases.

For this purpose we are looking for carriers of sSMC who would be willing to spend 10ml of peripheral blood to establish from that an immortalized cell line available for further sSMC-research (in case of interest please contact Dr. Liehr in Jena, Germany to obtain an informed consent and additional information).

All sSMC studies carried out in the Institute of Human Genetics Jena (Germany) are approved by the ethical commission of the Friedrich Schiller University (FSU) Jena, Germany - internal code 1457-12/04.


tl_files/tiny_templates/Bilder TL/Flags/0-figs.jpg

Figure 1. 46 normal chromosomes plus a small supernumerary marker chromosome = sSMC (arrow head)
Figure 2. Three possible different shapes of an sSMC - schematic drawing.
Figure 3. Until recently the only clinical correlations known between sSMC presence and clinical outcome based on data from 1998. This data is still broadly used in genetic counseling.
Figure 4. Potentially gene-dosage insensitive regions are labelled in green; potentially genedosage sensitive ones are labelled in red. Also on each chromosome sepcific subpage there are - if available - molecular data on the size of the genedosage insensitive regions.



UNIQUE = rare chromosome disorder support group developed several leaflets in connection with sSMC



for other sSMC-related patient support groups see here



sSMC in general



sSMC(1), esp. supernumerary ring chromosome 1



sSMC(8) part 1

sSMC(8) part 2



sSMC(12), esp. Pallister Killian syndrome (PKS)



iso-sSMC(15), esp. inv dup(15) syndrome



sSMC(16) part 1

sSMC(16) part 2



 => patient support groups related to sSMC


Partner of Dr. Liehr's lab:

UNIQUE = rare chromosome disorder support group:
Helpline: +44 (0) 1883 330766
Address: PO Box 2189, Caterham, Surrey, CR3 5GN, United Kingdom


Other support groups for genetic disorders

CONTACT a family - for families with disabled children:

LEONA - Verein für Eltern chromosomal geschädigter Kinder e.V. (German site):

Living with Trisomy: or

Valentin APAC:

Unique Danmark:

Chromosome Disorder Outreach (CDO):

sSMC(9)-related support groups

9TIPS Trisomy 9 International Parent Support: or

Trisomy 9:

sSMC(12)-related support groups

PKS Kids:

Pallister-Killian Syndrome foundation of Australia:

sSMC(15)- and UPD(15)-related support groups




Prader-Willi-Syndrom-Vereinigung (PWSV) Deutschland e.V. (German site):

Prader-Willi-Syndrome in Romania (Romanian site and English translation):

sSMC(16)-related support groups

DOC16; Disorders of chromosome 16:

sSMC(17)-related support groups


Dup-17p11-2, 17p11.2 Duplication:

sSMC(18)-related support groups

Chromosome 18 registry & research society:

Chromosome 18 Registry & Research Society (Europe):


sSMC(21)-related support groups

International Mosaic Down Syndrome Association

sSMC(22)-related support groups

Chromosome 22 Central - C22C; Chromosome 22 related disorders

KIDS-22q11 e.V. (German site):


sSMC(X) and (Y)-related support groups

Turner Syndrome Support Society (UK):