Summary

Deletion 2q37 or monosomy 2q37 is a chromosomal anomaly involving deletion of chromosome band 2q37 and manifests as three major clinical findings: developmental delay, skeletal malformations and facial dysmorphism. Incidence is estimated at less than 1 in 10,000 and more than 100 individuals have been reported. Most of the initially reported patients had an Albright hereditary osteodystrophy-like phenotype (referred to as AHO3) with developmental delay or intellectual deficit, short stature (23% of patients), a tendency toward obesity with age, and brachymetaphalangism (50% of patients). The following clinical features are also frequent: fifth finger clinodactyly and small feet/hands, syndactyly of the fingers or toes, persistent fetal finger pads and a single palmar crease, and microcephaly or macrocephaly. The facial dysmorphism is characteristic and defines the deletion 2q37 syndrome with a round face, sparse scalp hair, a prominent forehead, upslanting palpebral fissures, deep-set eyes, sparse and arched eyebrows, midface hypoplasia, a depressed nasal bridge, deficient nasal alae and prominent columella, V-shaped appearance of the nasal tip, thin vermillion border of the lips, and a high-arched palate. Nipples are often widely set, distally placed or supernumerary. Eczema is often present. Major malformations occur in 30% of patients with 2q37 deletions. Congenital heart, gastrointestinal (30% of patients), genitourinary (11% of cases) and central nervous system malformations (6% of patients) have been reported. Hypotonia is often present. Seizures are described in 35% of patients and behavioral anomalies are reported in about 30% of cases. Repetitive behavior and severe communication and social interaction deficits, stereotypic movements, intermittent aggressivity, hyperactivity, attention deficit disorder, obsessive-compulsive disorder and sleep disturbances are the characteristic features of a distinct subtype of autism associated with the 2q37 deletion. Thedeletion involves the terminal region of chromosome 2 with breakpoints at or within band 2q37. Band 2q37 contains three sub-bands with over 80 genes being located in the 2q37.1-q37.3 region. A few genotype-phenotype correlations have been identified including a critical region for the AHO-like phenotype and candidate genes for brachymetaphalangism, obesity and the autistic behavioral spectrum. The monosomy can be ``pure'' or can be associated with additional chromosomal imbalances. Diagnosis relies on cytogenetic analysis and molecular characterization. Screening for a translocation should also be conducted as the deletion may be the result of the transmission of a derivative chromosome. The differential diagnosis should include other segmental aneusomy syndromes and Prader-Willi syndrome (see this term). AHO (pseudohypoparathyroidism; PHP) and pseudo-PHP (PPHP; see these terms) should also be included in the differential diagnosis but calcium, phosphorus, and parathormone levels are in the normal range in patients with deletion 2q37. Antenatal diagnosis is feasible and genetic counseling should be proposed. Management of deletion 2q37 patients should be multidisciplinary and include a comprehensive evaluation of the major clinical criteria. Speech, physical and occupational therapy are required. The prognosis depends on the malformations (cardiac, cerebral or intestinal) associated with the 2q37 deletion.

Expert reviewer(s)

• Pr Martine DOCO-FENZY