Aplasia cutis congenita, congenital heart lesions, and frontonasal cysts in four successive generations

BTB domain mutations perturbing KCTD15 oligomerisation cause a distinctive frontonasal dysplasia syndrome

INTRODUCTION

KCTD15 encodes an oligomeric BTB domain protein reported to inhibit neural crest formation through repression of Wnt/beta-catenin signalling, as well as transactivation by TFAP2. Heterozygous missense variants in the closely related paralogue KCTD1 cause scalp-ear-nipple syndrome.

METHODS

Exome sequencing was performed on a two-generation family affected by a distinctive phenotype comprising a lipomatous frontonasal malformation, anosmia, cutis aplasia of the scalp and/or sparse hair, and congenital heart disease. Identification of a de novo missense substitution within KCTD15 led to targeted sequencing of DNA from a similarly affected sporadic patient, revealing a different missense mutation. Structural and biophysical analyses were performed to assess the effects of both amino acid substitutions on the KCTD15 protein.

RESULTS

A heterozygous c.310G>C variant encoding p.(Asp104His) within the BTB domain of KCTD15 was identified in an affected father and daughter and segregated with the phenotype. In the sporadically affected patient, a de novo heterozygous c.263G>A variant encoding p.(Gly88Asp) was present in KCTD15. Both substitutions were found to perturb the pentameric assembly of the BTB domain. A crystal structure of the BTB domain variant p.(Gly88Asp) revealed a closed hexameric assembly, whereas biophysical analyses showed that the p.(Asp104His) substitution resulted in a monomeric BTB domain likely to be partially unfolded at physiological temperatures.

CONCLUSION

BTB domain substitutions in KCTD1 and KCTD15 cause clinically overlapping phenotypes involving craniofacial abnormalities and cutis aplasia. The structural analyses demonstrate that missense substitutions act through a dominant negative mechanism by disrupting the higher order structure of the KCTD15 protein complex.

Large defects in aplasia cutis congenita treated by large-sized thin split-thickness skin grafting: long-term follow-up of 18 patients

OBJECTIVE

To evaluate the long-term results of using surgical large-sized thin split-thickness skin grafting to treat aplasia cutis congenita (ACC) in neonates.

METHODS

This study included 18 ACC neonates with large skin defects who underwent large-sized thin split-thickness skin grafting at our hospital from March 2002 to November 2011. The size of the lesion was >10% of the total body surface area (TBSA) in 16 patients, 7% of TBSA in one patient, and 3% of TBSA in another patient. The size of the skin graft was designed to be equal to or slightly larger than the size of the lesion.

RESULTS

Skin grafts in 16 patients who were followed for periods of 6 months-7 years after surgery showed good survival; however, two patients were lost to follow-up. The wound healed completely without scarring in five patients. One of the five patients who healed without scarring had failed previous conservative treatment. Several mild hypertrophic scars occurred in one patient, and flat, thin, shiny, soft, parchment-like scars were noted in five other patients. Dark red, hard, raised hypertrophic scars occurred in five patients who had partial necrosis in the skin graft after surgery.

CONCLUSION

A large-sized thin split-thickness skin graft can be used to effectively close a wound and permit healing to occur with reduced long-term scarring. This procedure is ideal for treating skin defects in patients with ACC.

Wide spectrum of congenital anomalies including choanal atresia, malformed extremities, and brain and spinal malformations in a girl with a de novo 5.6-Mb deletion of 13q12.11-13q12.13

A 2 ½-year-old girl with multiple congenital anomalies and a de novo 5.6-Mb deletion on chromosome 13q12.11-13q12.13 is reported. She showed choanal atresia, scalp aplasia cutis, mild dysmorphic features, severe malformation of the hands and feet, Sylvian aqueductal stenosis, hydrocephalus, small cerebellum with pointed cerebellar tonsils, cervical, lumbar and sacral clefting, single central incisor and mild developmental delay. The girl's anomalies were compared with: (A) one boy reported by each of Der Kaloustian et al. [2011] and Tanteles et al. [2011] with similar, albeit smaller, 2.1 to 2.9 Mb deletions in which the abnormalities consisted of mild facial dysmorphism, mild malformations of the fingers and/or toes, and developmental delay; (B) one girl reported by Friedman et al. [2006] with similar, albeit larger, 5.7 Mb deletion with mild developmental delay and haematological abnormalities; (C) one girl reported by Slee et al. [1991] with a deletion of band q12.2 in chromosome 13, who had Moebius syndrome with facial dysmorphism, high arched palate, micrognathia, and small tongue with no abnormalities of the extremities; and (D) seven additional individuals recorded in the DECIPHER 6.0 database who all had dysmorphic features and developmental delay plus a spectrum of clinical manifestations including deafness, ataxia/oculomotor apraxia, spasticity, small testes, and mild fingers' anomalies. The deleted region hereby reported encompassed 34 known genes, including GJA3, GJB2, and GJB6, which are responsible for autosomal recessive deafness, FGF9, which plays crucial roles in embryonic neurological development, and ATP8A2, which causes a cerebellar ataxia and disequilibrium syndrome.

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

The combination of aplasia cutis congenita (ACC) and terminal transverse limb defects (TTLD) is often referred to as the eponymous Adams-Oliver syndrome (AOS). The molecular basis of this disorder remains unknown, although the common occurrence of cardiac and vascular anomalies suggests a primary defect of vasculogenesis. Through the description of three previously unreported affected individuals, ascertained through the Adams-Oliver Syndrome European Consortium, we illustrate the phenotypic variability characteristically observed within extended families with AOS. Taken in combination with a detailed review of the available literature, we provide evidence for distinct clinical entities within the ACC/TTLD spectrum, which may reflect genetic heterogeneity within this spectrum of disorders.