Hypertrichosis cubiti (hairy elbows) and short stature: a recognisable association

Reprogramming of the epigenome in neurodevelopmental disorders

The etiology of neurodevelopmental disorders (NDDs) remains a challenge for researchers. Human brain development is tightly regulated and sensitive to cellular alterations caused by endogenous or exogenous factors. Intriguingly, the surge of clinical sequencing studies has revealed that many of these disorders are monogenic and monoallelic. Notably, chromatin regulation has emerged as highly dysregulated in NDDs, with many syndromes demonstrating phenotypic overlap, such as intellectual disabilities, with one another. Here we discuss epigenetic writers, erasers, readers, remodelers, and even histones mutated in NDD patients, predicted to affect gene regulation. Moreover, this review focuses on disorders associated with mutations in enzymes involved in histone acetylation and methylation, and it highlights syndromes involving chromatin remodeling complexes. Finally, we explore recently discovered histone germline mutations and their pathogenic outcome on neurological function. Epigenetic regulators are mutated at every level of chromatin organization. Throughout this review, we discuss mechanistic investigations, as well as various animal and iPSC models of these disorders and their usefulness in determining pathomechanism and potential therapeutics. Understanding the mechanism of these mutations will illuminate common pathways between disorders. Ultimately, classifying these disorders based on their effects on the epigenome will not only aid in prognosis in patients but will aid in understanding the role of epigenetic machinery throughout neurodevelopment.

Clinical and molecular spectrum of Wiedemann-Steiner syndrome, an emerging member of the chromatinopathy family

Wiedemann-Steiner syndrome (OMIM #605130) is a rare congenital malformation syndrome characterized by hypertrichosis cubiti associated with short stature; consistent facial features, including long eyelashes, thick or arched eyebrows with a lateral flare, wide nasal bridge, and downslanting and vertically narrow palpebral fissures; mild to moderate intellectual disability; behavioral difficulties; and hypertrichosis on the back. It is caused by heterozygous pathogenic variants in KMT2A. This gene has an established role in histone methylation, which explains the overlap of Wiedemann-Steiner syndrome with other chromatinopathies, a heterogeneous group of syndromic conditions that share a common trigger: The disruption of one of the genes involved in chromatin modification, leading to dysfunction of the epigenetic machinery.

Wiedemann-Steiner syndrome: Novel pathogenic variant and review of literature

Wiedemann-Steiner syndrome (WDSTS) is a very rare genetic disorder characterized by short stature, intellectual disability and distinctive facial appearance. We present a five-year-old boy who was diagnosed with WDSTS based on identification of a novel de novo pathogenic variant in the KMT2A gene (OMIM: 159555) by Whole Exome Sequencing and supported by some characteristic clinical features. Genotype and phenotype of the patient is compared with the earlier reported patients in the literature, in an attempt to broaden our knowledge of this rare syndrome.

Hypertrichosis cubiti, a case report and literature review

Hypertrichosis cubiti is an uncommon congenital hypertrichosis with links to genetic syndromes, both autosomal dominant and recessive, with variable penetrance and expressivity. It may also present in sporadic cases with no phenotypic abnormalities or family history.

Intellectual Disability: When the Hypertrichosis Is a Clue

The skin and the central and peripheral nervous system both derive from the ectoderm ridge. Therefore, several syndromes characterized by the presence of intellectual disability (ID) can be associated with specific congenital cutaneous manifestations. In this review, we list some of the most frequent diseases characterized by the presence of ID associated with hirsutism, which might be an incentive for the clinicians to pay attention to the ectodermal annexes in patients with ID.

A de novo Mutation in KMT2A (MLL) in monozygotic twins with Wiedemann-Steiner syndrome

Growth deficiency, psychomotor delay, and facial dysmorphism was originally described in a male patient in 1989 by Wiedemann et al. and later in 2000 by Steiner et al. Wiedemann-Steiner syndrome (WSS) has since been described only a few times in the literature, with the phenotypic spectrum both expanding and becoming more delineated with each patient reported. We report on the clinical and molecular features of monozygotic twins with a de novo mutation in KMT2A. Single nucleotide polymorphism (SNP) microarray was done on both twins and whole-exome sequencing was done using both parents and one of the affected twins. SNP microarray confirmed that they were monozygotic twins. A de novo heterozygous variant (p. Arg1083*) in the KMT2A gene was identified through whole-exome sequencing, confirming the diagnosis of WSS. In this study, we have identified a de novo mutation in KMT2A associated with psychomotor developmental delay, facial dysmorphism, short stature, hypertrichosis cubiti, and small kidneys. This finding in monozygotic twins gives specificity to the WSS. The description of more cases of WSS is needed for further delineation of this condition. Small kidneys with normal function have not been described in this condition in the medical literature before.

Syringomyelia and Bone Malformations in the Setting of Hypertrichosis Cubiti (Hairy Elbow Syndrome)

INTRODUCTION

The hypertrichosis cubiti also named "hairy elbow syndrome" is a benign anomaly which occurs as an isolated sign but sometime it may be associated with others abnormalities including short stature, facial dysmorphism, developmental delay and bone anomalies.

CASE REPORT

The Authors report on a girl 8 years old, who showed a classical hypertrichosis cubiti, tufts of peluria in the thoraco lumbar region, moderate scoliosis and bilateral large big toes. In correspondence with the tufts of spinal peluria the MRI displayed areas of syringomyelia.

CONCLUSION

A review of the cases of hypertrichosis cubiti associated to spine and bone anomalies is reported. This is the first report of the association of hypertrichosis cubiti with syringomyelia and large big toes. The presence of peluria in the elbow and/or in the thoraco lumbar region may be a clue of malformations of spine and bone. In conclusion the HC may be a simply aesthetic, benign anomaly, but may be also a clue of malformations affecting many organs including the spine and skeletal tissue.

De Novo variants in the KMT2A (MLL) gene causing atypical Wiedemann-Steiner syndrome in two unrelated individuals identified by clinical exome sequencing

Background

Wiedemann-Steiner Syndrome (WSS) is characterized by short stature, a variety of dysmorphic facial and skeletal features, characteristic hypertrichosis cubiti (excessive hair on the elbows), mild-to-moderate developmental delay and intellectual disability. [MIM#: 605130]. Here we report two unrelated children for whom clinical exome sequencing of parent-proband trios was performed at UCLA, resulting in a molecular diagnosis of WSS and atypical clinical presentation.

Case presentation

For patient 1, clinical features at 9 years of age included developmental delay, craniofacial abnormalities, and multiple minor anomalies. Patient 2 presented at 1 year of age with developmental delay, microphthalmia, partial 3–4 left hand syndactyly, and craniofacial abnormalities. A de novo missense c.4342T>C variant and a de novo splice site c.4086+G>A variant were identified in the KMT2A gene in patients 1 and 2, respectively.

Conclusions

Based on the clinical and molecular findings, both patients appear to have novel presentations of WSS. As the hallmark hypertrichosis cubiti was not initially appreciated in either case, this syndrome was not suspected during the clinical evaluation. This report expands the phenotypic spectrum of the clinical phenotypes and KMT2A variants associated with WSS.

Hypertrichosis

Hypertrichosis is hair growth that is abnormal for the age, sex, or race of an individual, or for a particular area of the body. Recognized forms of hypertrichosis are reviewed. Hirsutism, which is male-pattern hair growth in a female or child, is not included in this review. Hypertrichosis is categorized as congenital or acquired, and regional or generalized. Methods of managing hypertrichosis are also briefly reviewed

A new case of hairy elbows syndrome (Hypertrichosis cubiti)

Hypertrichosis cubiti, also named hairy elbows syndrome (HES), is an uncommon variety of congenital, circumscribed hypertrichosis in which a remarkable amount of long vellus hair is localized on the extensor surfaces of the upper extremities. Usually, this condition appears in infancy, increases during early childhood, and regresses spontaneously at puberty. The mode of inheritance is not elucidated, and the condition presents in a sporadic or familial form. In most patients HES is not associated with any other physical abnormalities, although short stature and other developmental disorders have been described in some. An 8-year-old girl affected with HES is reported. The literature on this subject is reviewed, and some clinical and etiopathogenic aspects are discussed.

Hypertrichosis "cubiti" with facial asymmetry

Hypertrichosis of the elbow region may be the only abnormality in hypertrichosis cubiti (hairy elbow syndrome). Only 6 cases have been reported; 2 Amish sibs also had additional short stature and, in the most recent case report, a patient had asymmetry of the face, generalized hypotonia, ptosis, epicanthic folds, highly arched palate, and delayed growth and development. The child reported here also had asymmetry of facial growth, ptosis, delayed speech development, and hypertrichosis in a patchy distribution which included the elbow regions, face, trunk, and thighs. There was no family history of hypertrichosis, and the karyotype of cultured fibroblasts was normal in the skin of an area of hypertrichosis. These patients appear to have a distinct condition compared to other hypertrichosis syndromes.

Hairy elbows syndrome (familial hypertrichosis cubiti)

Hairy elbows syndrome was first described by Beighton in 1970. An association with short stature has been suggested. A 5-year-old girl with the hairy elbows syndrome who is otherwise healthy is described. Her height is on the 25th centile and appropriate for her family, in which no other members are affected. The mode of inheritance of this disorder remains to be determined.