Distal Monosomy 10p

Distal monosomy 10p is a rare chromosomal disorder in which the tip of the short arm (p arm) of chromosome 10 is deleted resulting in a variable phenotype depending on the size of the deletion. The deletion may involve only the terminal 10p15 band, or extend towards the centromere to bands 10p14 or 10p13.

Epidemiology

Around 50 cases of pure distal monosomy 10p have been reported.

Clinical description

Distal monosomy 10p encompassing the 10p13 band is associated with cardiac malformations and immune anomalies that overlap with the anomalies reported in the deletion 22q11 syndrome (DiGeorge syndrome/velocardiofacial syndrome spectrum (DGS/VCFS); see this term) with hypoparathyroidism, hypocalcemia, congenital conotruncal heart defects, thymus hypoplasia leading to T-cell deficiency and intellectual deficit. More than 25 patients have been reported with del(10)(p13). In addition to the anomalies related to the DiGeorge syndrome (e.g. conotruncal malformation with thymic hypoplasia), these patients often show an abnormally shaped skull, microcephaly, a long face, high forehead, broad nasal bridge, downslanting palpebral fissures, anteverted nares, hand and foot abnormalities, genitourinary anomalies, hearing loss and severe psychomotor retardation, resulting in a clinical picture that clearly differs from that of the classic 22q11 deletion syndrome. However, due to the similarities in the malformations observed in the two syndromes, del(10)(p13) is referred to as DGS2. The critical region for DGS2 has been mapped to within a 1cM interval in 10p13 which contains the CUGBP2 gene, a candidate gene for developmental heart defects. Smaller deletions involving the region 10p14-pter have been described in < than 10 patients. Some of these patients exhibited the triad: Hypoparathyroidism, sensorineural Deafness, and Renal anomaly (HDR syndrome; see this term). Haploinsufficiency for the trans-acting T-cell-specific transcription factor GATA-3 (encoded by the GATA3 gene, and mapped to the 10p14-pter region) is responsible for this phenotype. Pure subtelomeric deletions involving 10p15-ter are very rare (< 6 children reported so far).

Etiology

The phenotype remains unclear: low birth weight, persistent growth delay, mild psychomotor retardation and hypotonia have been reported, together with single reports of ventricular septal defect, hydrocephalus and hypogenitalia. Distal monosomy 10p generally occurs de novo or may be associated with a parental translocation.

Diagnostic methods

Diagnosis requires cytogenetic analysis and molecular characterization and should include a search for a translocation because deletion may be the result of transmission of a derivative chromosome.

Differential diagnosis

The differential diagnosis for patients with distal monosomy 10p should include deletion 22q11 syndrome and other causes of hypoparathyroidism, depending on the phenotype.

Antenatal diagnosis

Prenatal diagnosis is feasible and genetic counseling should be proposed and depends on the cytogenetic rearrangement responsible for the deletion (de novo or translocation).

Management and treatment

Management of 10p monosomy includes a comprehensive evaluation of the major clinical criteria: developmental delay, feeding difficulties, hypocalcemia, deafness, cardiac defects, and recurrent infections. Pediatricians, neurologists, nephrologists and endocrinologists should be involved as appropriate. Developmental assessments with speech, physical and occupational therapists are required.

Prognosis

The prognosis is variable, depending on the malformations associated.