Testicular sex cord-stromal tumor in a boy with 2q37 deletion syndrome

Genotype and phenotype correlation in 103 individuals with 2q37 deletion syndrome reveals incomplete penetrance and supports HDAC4 as the primary genetic contributor

The 2q37 deletion syndrome, also described in the literature as brachydactyly-mental retardation syndrome (MIM 600430), is caused by deletion or haploinsufficiency of the HDAC4 gene, which encodes the histone deacetylase 4 protein. Although the most commonly described hallmark features of the 2q37 deletion syndrome include brachydactyly type E, developmental delay, obesity, autistic features, and craniofacial or skeletal dysmorphism, a literature review of 101 published cases plus two newly reported individuals indicates that there is a high degree of variability in the presence of some of the features that are considered the most characteristic of the syndrome: overweight and obesity (34%), cognitive-behavioral issues (79%), dysmorphic craniofacial features (86%), and type E brachydactyly (48%). These features overlap with other neurodevelopmental conditions, including Smith-Magenis syndrome (SMS), and may be incompletely penetrant or demonstrate variable expressivity, depending on the specific chromosomal anomaly. With the advent of fluorescence in situ hybridization (FISH), array-based comparative genomic hybridization, and next-generation DNA sequencing, more detailed molecular diagnoses are possible than in years past, enabling refined characterization of the genotype-phenotype correlation for subjects with 2q37 deletions. In addition, investigations into molecular and gene expression networks are expanding in neurodevelopmental conditions, and we surveyed HDAC4 downstream gene expression by quantitative real-time polymerase chain reaction, further implicating HDAC4 in its role in the regulation of RAI1. Correlation of clinical data defining the impact on downstream gene expression and the potential clinical associations across neurodevelopment will improve our understanding of these complex conditions and potentially lead to common therapeutic approaches.

Brachydactyly mental retardation syndrome with growth hormone deficiency

Deletion of chromosome 2q37 results in a rare congenital syndrome known as brachydactyly mental retardation (BDMR) syndrome; a syndrome which has phenotypes similar to Albright hereditary osteodystrophy (AHO) syndrome. In this report, we describe a patient with AHO due to microdeletion in long arm of chromosome 2 [del(2)(q37.3)] who had growth hormone (GH) deficiency, which is a unique feature among reported BDMR cases. This case was presented with shortening of the fourth and fifth metacarpals which along with AHO phenotype, brings pseudopseudohypoparathyroidism (PPHP) and pseudohypoparathyroidism type Ia (PHP-Ia) to mind; however, a genetic study revealed del(2)(q37.3). We recommend clinicians to take BDMR in consideration when they are faced with the features of AHO; although this syndrome is a rare disease, it should be ruled out while diagnosing PPHP or PHP-Ia. Moreover, we recommend evaluation of IGF 1 level and GH stimulation test in patients with BDMR whose height is below the 3rd percentile.

LEARNING POINTS

Clinicians must have brachydactyly mental retardation (BDMR) syndrome in consideration when they are faced with the features of Albright hereditary osteodystrophy.Although BDMR syndrome is a rare disease, it should be ruled out while diagnosing PPHP or PHP-Ia.Evaluation of IGF1 level in patients diagnosed with BDMR whose height is below the 3rd percentile is important.