Trisomy 10p (ORPHA:171929)
Trisomy 10p is a syndrome of mental retardation/multiple congenital malformations (MR-MCA) that is caused by the total or partial duplication of the short arm of chromosome 10.
Epidemiology
Around 50 cases have been described in the literature.
Clinical description
In complete trisomy 10p, the anomalies are present at birth. Children are usually dolichocephalic with a high and prominent forehead, contrasting with a small face, a distinctive implantation of hair that grows backwards, large sutures and a large anterior fontanelle, eyebrows that are fine, arched and that extend to the temples, a large nasal bridge that becomes prominent. The mouth is triangular, with not very apparent fleshy parts, the chin is round, often small and not well defined. The ears are large and low. A third of cases have a cleft lip and/or palate. Osteoarticular anomalies are frequent, including ligament hyperlaxity, flexion deformations of limbs, and club feet. Cardiac, renal (renal cystic dysplasia), ocular (coloboma, microphthalmia) and bone malformations have been reported. Hypochromic anemia is sometimes observed. Development is affected by severe intellectual and motor deficiency, and muscular hypotonia and hypotrophia.
Etiology
The majority of cases are a result of the malsegregation of a familial balanced translocation. The most frequent break point is located at the level of p11 band, but it can be more distal and result in partial trisomy. Other mechanisms can also be involved (pericentric inversion, duplication de novo, supernumerary chromosome...).
Diagnostic methods
The observation of a developmental anomaly associated with congenital anomalies leads to performing a karyotype which shows total or partial duplication of the short arm of chromosome 10, often associated with another imbalance. The identity of the chromosomal segment can be confirmed using in situ hybridization with probes specific to 10p. The parents' karyotype is essential in order to determine how the disease has occurred.
Differential diagnosis
Differential diagnoses include other syndromes of developmental delay with dysmorphism and congenital malformations.
Antenatal diagnosis
Prenatal diagnosis is possible, after the birth of the first affected child or after warning signs from an ultrasound, by choronic villus sampling (CVS) or amniocentesis in cases of structural anomalies in one of the parents.
Genetic counseling
In cases where the anomaly occurred de novo, the risk of recurrence in siblings is weak. When a structural anomaly is present in one of the parents, the risk will be evaluated depending on the type of anomaly.
Management and treatment
There is no specific treatment. Early multidisciplinary management and special education is necessary.
Prognosis
The prognosis is severe. A quarter to a third of patients die in the neonatal period. In other cases the progression is marked by severe intellectual and motor deficiency, and muscular hypotonia and hypotrophia. Partial trisomy with a break point at p13 result in similar characteristics but serious malformations are less frequent.

                            Last update: 
                            February 2009


                            - Expert reviewer(s): 
                            Dr Catherine TURLEAU