The spectra of clinical phenotypes in aplasia cutis congenita and terminal transverse limb defects

DOCK6 mutations are responsible for a distinct autosomal-recessive variant of Adams-Oliver syndrome associated with brain and eye anomalies

Adams-Oliver syndrome (AOS) is characterized by the association of aplasia cutis congenita with terminal transverse limb defects, often accompanied by additional cardiovascular or neurological features. Both autosomal-dominant and autosomal-recessive disease transmission have been observed, with recent gene discoveries indicating extensive genetic heterogeneity. Mutations of the DOCK6 gene were first described in autosomal-recessive cases of AOS and only five DOCK6-related families have been reported to date. Recently, a second type of autosomal-recessive AOS has been attributed to EOGT mutations in three consanguineous families. Here, we describe the identification of 13 DOCK6 mutations, the majority of which are novel, across 10 unrelated individuals from a large cohort comprising 47 sporadic cases and 31 AOS pedigrees suggestive of autosomal-recessive inheritance. DOCK6 mutations were strongly associated with structural brain abnormalities, ocular anomalies, and intellectual disability, thus suggesting that DOCK6-linked disease represents a variant of AOS with a particularly poor prognosis.

We have contact: endothelial cell-smooth muscle cell interactions

Blood vessels are composed of two primary cell types, endothelial cells and smooth muscle cells, each providing a unique contribution to vessel function. Signaling between these two cell types is essential for maintaining tone in mature vessels, and their communication is critical during development, and for repair and remodeling associated with blood vessel growth. This review will highlight the pathways that endothelial cells and smooth muscle cells utilize to communicate during vessel formation and discuss how disruptions in these pathways contribute to disease.

Mutations in NOTCH1 cause Adams-Oliver syndrome

Notch signaling determines and reinforces cell fate in bilaterally symmetric multicellular eukaryotes. Despite the involvement of Notch in many key developmental systems, human mutations in Notch signaling components have mainly been described in disorders with vascular and bone effects. Here, we report five heterozygous NOTCH1 variants in unrelated individuals with Adams-Oliver syndrome (AOS), a rare disease with major features of aplasia cutis of the scalp and terminal transverse limb defects. Using whole-genome sequencing in a cohort of 11 families lacking mutations in the four genes with known roles in AOS pathology (ARHGAP31, RBPJ, DOCK6, and EOGT), we found a heterozygous de novo 85 kb deletion spanning the NOTCH1 5' region and three coding variants (c.1285T>C [p.Cys429Arg], c.4487G>A [p.Cys1496Tyr], and c.5965G>A [p.Asp1989Asn]), two of which are de novo, in four unrelated probands. In a fifth family, we identified a heterozygous canonical splice-site variant (c.743-1 G>T) in an affected father and daughter. These variants were not present in 5,077 in-house control genomes or in public databases. In keeping with the prominent developmental role described for Notch1 in mouse vasculature, we observed cardiac and multiple vascular defects in four of the five families. We propose that the limb and scalp defects might also be due to a vasculopathy in NOTCH1-related AOS. Our results suggest that mutations in NOTCH1 are the most common cause of AOS and add to a growing list of human diseases that have a vascular and/or bony component and are caused by alterations in the Notch signaling pathway.

Conservative Healing of an 11 × 9-cm Aplasia Cutis Congenita of the Scalp with Bone Defect

Objectives Aplasia cutis congenita is a rare congenital condition, and it is difficult to find scientific support for optimal treatment strategies. In addition, these may vary due to defect size, tissue layers involved, contemporary malformations, and the physiologic status of the affected child.

Clinical Presentation This case report describes complete skin coverage in 20 weeks and uneventful healing of a large 11 × 9-cm defect of the vertex, involving both skin and skull bone, using conservative treatment. To prevent infection and promote healing, the defect was kept moist and covered at all times, and it was treated with surgical debridement when necessary. For infection control, ionized silver-coated dressings were used in addition to prophylactic antibiotics over the first 3.5 weeks. Follow-up was 2 years.

Conclusion Surgical treatment is usually preferred for larger aplasia cutis congenita defects, but it is accompanied with potential risks and will exacerbate secondary reconstruction of alopecia or skull bone defects. This case shows that even very complex defects may be treated conservatively.

Diffuse angiopathy in Adams-Oliver syndrome associated with truncating DOCK6 mutations

Adams-Oliver syndrome (AOS) is a rare malformation syndrome characterized by the presence of two anomalies: aplasia cutis congenita of the scalp and transverse terminal limb defects. Many affected individuals also have additional malformations, including a variety of intracranial anomalies such as periventricular calcification in keeping with cerebrovascular microbleeds, impaired neuronal migration, epilepsy, and microcephaly. Cardiac malformations can be present, as can vascular dysfunction in the forms of cutis marmorata telangiectasia congenita, pulmonary vein stenoses, and abnormal hepatic microvasculature. Elucidated genetic causes include four genes in different pathways, leading to a model of AOS as a multi-pathway disorder. We identified an infant with mild aplasia cutis congenita and terminal transverse limb defects, developmental delay and a severe, diffuse angiopathy with incomplete microvascularization. Whole-genome sequencing documented two rare truncating variants in DOCK6, a gene associated with a type of autosomal recessive AOS that recurrently features periventricular calcification and impaired neurodevelopment. We highlight an unexpectedly high frequency of likely deleterious mutations in this gene in the general population, relative to the rarity of the disease, and discuss possible explanations for this discrepancy.

Isolated terminal limb reduction defects: extending the clinical spectrum of Adams-Oliver syndrome and ARHGAP31 mutations

Adams-Oliver syndrome (AOS; OMIM 100300) typically comprises a combination of congenital scalp defects and terminal transverse limb defects. Recently, mutations in ARHGAP31 and RBPJ have been found causing autosomal dominant forms of AOS. We describe a four-generation pedigree with isolated terminal limb defects and a truncating mutation in ARHGAP31. This finding underscores the relevance of sequencing ARHGAP31 in similar cases of isolated limb defects, irrespective of the presence of a complete AOS phenotype. We also highlight the variability of clinical features among mutation carriers, ranging from severe reduction defects to mild as well as clinically unaffected cases suggesting reduced penetrance.

Autosomal recessive Adams-Oliver syndrome caused by homozygous mutation in EOGT, encoding an EGF domain-specific O-GlcNAc transferase

Autosomal recessive Adams-Oliver syndrome was diagnosed in three remotely related Bedouin consanguineous families. Genome-wide linkage analysis ruled out association with known Adams-Oliver syndrome genes, identifying a single-homozygosity ∼1.8-Mb novel locus common to affected individuals (LOD score 3.37). Whole-exome sequencing followed by Sanger sequencing identified only a single mutation within this locus, shared by all affected individuals and found in patients from five additional apparently unrelated Bedouin families: a 1-bp deletion mutation in a predicted alternative splice variant of EOGT, leading to a putative truncated protein. RT-PCR demonstrated that the EOGT-predicted alternative splice variant is ubiquitously expressed. EOGT encodes EGF-domain-specific O-linked N-acetylglucosamine transferase, responsible for extracellular O-GlcNAcylation of epidermal growth factor-like domain-containing proteins, and is essential for epithelial cell-matrix interactions. F-actin staining in diseased fibroblasts showed apparently intact cell cytoskeleton and morphology, suggesting the EOGT mutation acts not through perturbation of cytoskeleton but through other mechanisms yet to be elucidated.

Expanding the phenotype of cardiovascular malformations in Adams-Oliver syndrome

We describe a newborn with a phenotype consistent with Adams-Oliver syndrome and truncus arteriosus. Although cardiovascular malformations associated with this syndrome have been previously published in the literature, this is the first description of truncus arteriosus in a patient with Adams-Oliver syndrome. We review other reports of Adams-Oliver syndrome previously described with cardiovascular malformations, consider possible genetic and embryologic mechanisms, and emphasize the need for cardiology consultation when a diagnosis of Adams-Oliver syndrome is suspected in the differential diagnosis.

Mutations in EOGT confirm the genetic heterogeneity of autosomal-recessive Adams-Oliver syndrome

Adams-Oliver syndrome (AOS) is a rare, autosomal-dominant or -recessive disorder characterized primarily by aplasia cutis congenita and terminal transverse limb defects. Recently, we demonstrated that homozygous mutations in DOCK6 cause an autosomal-recessive form of AOS. In this study, we sought to determine the contribution of DOCK6 mutations to the etiology of AOS in several consanguineous families. In two of the five families studied, we identified two homozygous truncating mutations (a splice-site mutation and a frameshift duplication). DOCK6 sequencing revealed no mutation in the remaining three families, consistent with their autozygosity mapping and linkage-analysis results, which revealed a single candidate locus in 3p14.1 on three different haplotype backgrounds in the three families. Indeed, exome sequencing in one family revealed one missense mutation in EOGT (C3orf64), and subsequent targeted sequencing of this gene revealed a homozygous missense mutation and a homozygous frameshift deletion mutation in the other two families. EOGT encodes EGF-domain-specific O-linked N-acetylglucosamine (O-GlcNAc) transferase, which is involved in the O-GlcNAcylation (attachment of O-GlcNAc to serine and threonine residues) of a subset of extracellular EGF-domain-containing proteins. It has a documented role in epithelial-cell-matrix interactions in Drosophila, in which deficiency of its ortholog causes wing blistering. Our findings highlight a developmental role of O-GlcNAcylation in humans and expand the genetic heterogeneity of autosomal-recessive AOS.

Dilemmas and challenges in the management of a neonate with Adams-Oliver syndrome with infected giant aplasia cutis lesion and exsanguination: a case-based update

BACKGROUND

Aplasia cutis is a rare developmental anomaly usually involving the calvarium, associated with a variable extent of defective formation of the scalp. Adams-Oliver syndrome is a condition mainly characterized by the congenital absence of skin, known as "aplasia cutis" which is usually limited to the vertex scalp and transverse limb defects.

CASE REPORT

A 17-day-old term female neonate was referred to us with an infected scalp lesion of the vertex. The lesion which is about 10 × 9 cm had signs of infection with necrotic eschar. We started the neonate on systemic parenteral antibiotics with local dressings. On day 3 of conservative management, the neonate had exsanguination due to bleeding from the midline with severe hemodynamic compromise requiring cardiopulmonary resuscitation. After controlling the bleeding with local tamponade and resuscitating the child, she was taken for early surgery. Debridement and bipedicled rotation flap of the scalp to cover the raw area was performed. On day 18, the flap started showing signs of necrosis. The neonate was taken up for debridement, and subsequently, maternal allograft of split-thickness skin was placed as a temporary wound cover. Meanwhile, the wound showed progressive epithelialization. At 1 year, the patient continued to have a non-healing area, which was later successfully covered with a split-thickness skin graft. We plan to revaluate the need for cranioplasty at around 3-4 years of age.

DISCUSSION

We discuss the dilemmas and challenges involved in the successful management of a neonate with Adams-Oliver syndrome with infected aplasia cutis and an episode of life-threatening exsanguination.

CONCLUSION

Aplasia cutis is a rare developmental anomaly usually involving the calvarium, associated with defective formation of the scalp to a varying extent and severity, requiring various timely strategies.

A 6-week-old girl with a scalp lesion

CME EDUCATIONAL OBJECTIVES: 1.Identify the clinical features of aplasia cutis congenita (ACC).2.Understand the differential diagnosis of ACC.3.Recognize features of concern for underlying associations of ACC. A 6-week-old girl presented to the dermatology clinic for evaluation of a scalp lesion. She was born full-term by vaginal delivery to a 27-year-old healthy mother with normal prenatal labs. The delivery was complicated by prolonged rupture of membranes and a scalp electrode was placed at hour 20 of labor. Forceps or other instrumentation were not used during delivery. In the general care nursery, the infant was noted to have a scalp lesion. No bleeding or drainage was ever noted from the area. The lesion remained unchanged since birth with no intermittent enlargement noted. Review of systems was unremarkable. Family history was noncontributory.

Multiple aplasia cutis congenita lesions located along Blaschko's lines in a patient with tetralogy of Fallot-A

BACKGROUND

Aplasia cutis congenita (ACC) is a congenital absence of skin, and a single alopecic lesion on the scalp is the most common form.

MAIN OBSERVATION

We present a case of ACC with tetralogy of Fallot-A. Differetial diagnosis included Adams-Oliver syndrome and nevus psiloliparus. Interestingly, our patient showed multiple ACC lesions, which were located along Blaschko's lines.

CONCLUSIONS

As far as we know, our case is the third case of ACC with tetralogy of Fallot-A. Also, this is the first case of ACC associated with Blaschko's lines.

A developmental and genetic classification for malformations of cortical development: update 2012

Malformations of cerebral cortical development include a wide range of developmental disorders that are common causes of neurodevelopmental delay and epilepsy. In addition, study of these disorders contributes greatly to the understanding of normal brain development and its perturbations. The rapid recent evolution of molecular biology, genetics and imaging has resulted in an explosive increase in our knowledge of cerebral cortex development and in the number and types of malformations of cortical development that have been reported. These advances continue to modify our perception of these malformations. This review addresses recent changes in our perception of these disorders and proposes a modified classification based upon updates in our knowledge of cerebral cortical development.

Cutis aplasia: perioperative management and case report

Aplasia cutis congenita, a rare congenital disorder involving defects of some or all of the layers of the cranium, is associated with potential life-threatening complications. Although treatment involves both nonsurgical and surgical techniques, the importance of perioperative management cannot be overstressed. A multidisciplinary team, including personnel from nursing, neonatology, pediatrics, radiology, neurosurgery, and plastic surgery services, diagnosed aplasia cutis congenita and planned local wound care, surgical correction, and prevention of potentially life-threatening complications in a 1-day-old boy with a 6×5-cm full-thickness scalp defect.

Aplasia cutis congenita and other anomalies associated with methimazole exposure during pregnancy

Aplasia cutis congenita (ACC) is a congenital defect consisting of a circumscribed absence of skin that usually involves the scalp. The etiology is uncertain, and several teratogenic agents such as methimazole have been involved. We report two cases of ACC and other anomalies in newborns exposed to methimazole during pregnancy.

F. Recessive mutations in DOCK6, encoding the guanidine nucleotide exchange factor DOCK6, lead to abnormal actin cytoskeleton organization and Adams-Oliver syndrome

Adams-Oliver syndrome (AOS) is defined by the combination of aplasia cutis congenita (ACC) and terminal transverse limb defects (TTLD). It is usually inherited as an autosomal-dominant trait, but autosomal-recessive inheritance has also been documented. In an individual with autosomal-recessive AOS, we combined autozygome analysis with exome sequencing to identify a homozygous truncating mutation in dedicator of cytokinesis 6 gene (DOCK6) which encodes an atypical guanidine exchange factor (GEF) known to activate two members of the Rho GTPase family: Cdc42 and Rac1. Another homozygous truncating mutation was identified upon targeted sequencing of DOCK6 in an unrelated individual with AOS. Consistent with the established role of Cdc42 and Rac1 in the organization of the actin cytoskeleton, we demonstrate a cellular phenotype typical of a defective actin cytoskeleton in patient cells. These findings, combined with a Dock6 expression profile that is consistent with an AOS phenotype as well as the very recent demonstration of dominant mutations of ARHGAP31 in AOS, establish Cdc42 and Rac1 as key molecules in the pathogenesis of AOS and suggest that other regulators of these Rho GTPase proteins might be good candidates in the quest to define the genetic spectrum of this genetically heterogeneous condition.

Adams-Oliver syndrome associated with bilateral anterior polar cataracts and optic disk drusen

Adams-Oliver syndrome (AOS) (MIM 100300) was first described in 1945 as a condition of terminal transverse limb defects and aplasia cutis congenita. Since then, its clinical features have been found to be highly variable and include cardiac defects, abdominal wall defects, vascular malformations, brain abnormalities, and ocular anomalies. We report the case of a 3-year-old girl with AOS who was also found to have bilateral anterior polar cataracts and pseudopapilledema secondary to optic disk drusen. To the best of our knowledge, this is the first case of bilateral anterior polar cataracts and pseudopapilledema secondary to optic disk drusen to be reported in association with the AOS.

Gain-of-function mutations of ARHGAP31, a Cdc42/Rac1 GTPase regulator, cause syndromic cutis aplasia and limb anomalies

Regulation of cell proliferation and motility is essential for normal development. The Rho family of GTPases plays a critical role in the control of cell polarity and migration by effecting the cytoskeleton, membrane trafficking, and cell adhesion. We investigated a recognized developmental disorder, Adams-Oliver syndrome (AOS), characterized by the combination of aplasia cutis congenita (ACC) and terminal transverse limb defects (TTLD). Through a genome-wide linkage analysis, we detected a locus for autosomal-dominant ACC-TTLD on 3q generating a maximum LOD score of 4.93 at marker rs1464311. Candidate-gene- and exome-based sequencing led to the identification of independent premature truncating mutations in the terminal exon of the Rho GTPase-activating protein 31 gene, ARHGAP31, which encodes a Cdc42/Rac1 regulatory protein. Mutant transcripts are stable and increase ARHGAP31 activity in vitro through a gain-of-function mechanism. Constitutively active ARHGAP31 mutations result in a loss of available active Cdc42 and consequently disrupt actin cytoskeletal structures. Arhgap31 expression in the mouse is substantially restricted to the terminal limb buds and craniofacial processes during early development; these locations closely mirror the sites of impaired organogenesis that characterize this syndrome. These data identify the requirement for regulated Cdc42 and/or Rac1 signaling processes during early human development.

Do children with Adams-Oliver syndrome require endocrine follow-up? New information on the phenotype and management

Adams-Oliver syndrome (AOS) is a rare genetic condition in which the main diagnostic criteria are terminal transverse limb defects and aplasia cutis congenita. Within the spectra of the clinical phenotype of AOS, anthropometric abnormalities have also been reported. We present growth pattern along with hormonal assays in three patients with AOS, one being treated with growth hormone (GH). In Patient 1 (a boy, age 1.9 years), with delayed psychomotor development, epilepsy, deficits of body mass and height, cryptorchidism, low insulin-like growth factor (IGF-1) levels were found and magnetic resonance imaging (MRI) revealed hypoplasia of midline structures of the central nervous system (CNS). In Patient 2 (a girl, age 3.6 years) no significant abnormalities in development, body mass, height or neuroimaging were found. In Patient 3 (a girl, age 8.2 years), with delayed psychomotor development and short stature, low IGF-1 levels and partial GH deficiency were found; MRI revealed small pituitary and polymicrogyria. The girl started GH treatment, improving height velocity and gross coordination. Based on these observations, it seems that intensity of auxologic and hormonal deficits in children with AOS is associated with CNS lesions. Hence, there are indications for neuroimaging and interdisciplinary follow-up of psychomotor development, growth and puberty in this subset of patients with AOS.