Tetrasomy 9p syndrome

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Tetrasomy 9p syndrome

ORPHA:3310Malformation syndrome

Also called Isochromosome 9p

What it is

Tetrasomy 9p is a rare autosomal anomaly characterized by pre- and postnatal growth retardation, psychomotor delay, mild to moderate intellectual disability, hypotonia, microcephaly, dysmorphic features (ocular hypertelorism, low-set, malformed ears, bulbous/beaked nose, microretrognathia, enophthalmos/micropthalmia, epicanthus, strabismus), cleft lip/palate, skeletal abnormalities (hypoplastic nails/distal phalanges, short stature, short neck, contractures), congenital heart defects, renal and urogenital malformations (renal hypoplasia, genital hypoplasia, cryptorchidism).

Key facts

Prevalence
<1 / 1 000 000
Age of onset
Antenatal, Neonatal
Classified as
Malformation syndrome

Prevalence figures describe populations, not individuals, and are often estimates from a single study. Where the figure is an incidence or a birth prevalence, it says so.

Signs and symptoms

These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.

ICD-10 codes

Q99.8filed under a broader ICD-10 category — shared with 42 other rare diseases

ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.

Related health topics

Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.

Cross-references

GARD 42MESH C538027MONDO 0018030UMLS C0795832

Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.

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