6 for 1000 births
The incidence of balanced chromosomal defects is 2/1000; their sibs
Unknown but suspected due to the recurrence of trisomy 21 (1 to 2%).
Ovulation induction, ionizing radiations, antimitotic agents
Karyotype on fibroblasts(umbilical cord, lung, muscle) if the etiology
in unknown or when one suspects a chromosomal disease ( for instance in
dysmorphic syndromes and / or visceral anomalies); a complete anatomo-pathological
examination is indicated ( foeto-pathology).
Tissues: amniotic fluid cells obtained by amniocentesis, chorionic
villi, lymphocytes obtained by cordocentesis.
De novo chromosomal anomalies ( on tumour cells) while the constitutional
karyotype remains normal ( note: although neoplasic diseases are considered
as acquired, some have a hereditary component; see:
those anomalies are characteristic, often pathognomonic in leukemias
and sarcomas: t(9;22) in chronic myelogeneous leukemia, t(3;13)(q35;q14)
in the alveolar rhabdosarcoma].
Those anomalies may confirm the diagnosis and help defining the prognosis.
However several are identified and most give little insight on solid tumours.
Role of oncogens (ABL in 9q34, MLL in 11q23, ETV6 in 12p13, AML 1 in
21q22 ), and or tumour suppressor genes (Rb in 13q14, P53 in 17p13) ?
Tissues: peripheral lymphocytes, bone marrow, lymph nodes, solid tumours,
pleural effusion, ascites,..
Huret JL, Dallaire L
Atlas of Genetics and Cytogenetics in Oncology and Haematology 2002-09-01
Chromosomal Disorders - Karyotype Indications
Online version: http://atlasgeneticsoncology.org/teaching/30079/chromosomal-disorders-karyotype-indications