Heterotopic respiratory mucosa as a potential source of ectopic Sonic hedgehog (SHH) in the development of complex radial polydactyly and ulnar dimelia.

We report eight cases of complex radial polydactyly and/or ulnar dimelia each with a fistulous lesion of heterotopic respiratory mucosa in radial-anterior skin ranging from shoulder to wrist. Although speculative, the coincidence of these rare conditions suggests a mechanistic relationship.

Distal Dorsal Dimelia: A Disturbance of Dorsal-Ventral Digit Development.

PURPOSE: Congenital palmar nail (distal dorsal dimelia [dDD]) of the hand is a rare malformation most commonly affecting the little finger. The purpose of this report was to review the features and associations of this rare disorder and discuss the suspected underlying etiology in light of our current understanding of developmental biology. METHODS: In this retrospective cohort study from 3 practices, we describe our collective experience and review the reported literature on this disorder both as an isolated condition and in conjunction with other anomalies. RESULTS: We examined 15 fingers with dDD, 5 of which involved little fingers. We also found dDD in 6 cases with radial polydactyly (preaxial polydactyl type II [PPD2]) and in 1 case of cleft hand involving digits adjacent to the clefted web space (the index and middle fingers). Cases of little finger dDD were also associated with prominent clefting of the adjacent web space in 4 of 5 cases. All cases had stiffness of the interphalangeal joints and loss of palmar creases consistent with dorsalization of the palmar aspect of the digit. When combined with 63 fingers reported in the literature with dDD, 3 patterns were evident. The most common form occurred in little fingers (n = 50; 64%; dDDu). The next most common form was reported in association with cleft hands (n = 16; 21%; dDDc). Radial digits in association with either radial polydactyly (PPD2) or radial longitudinal deficiency were also susceptible to dDD (n = 12; 15%; dDDr). CONCLUSIONS: Congenital dDD is a disturbance of terminal dorsal-ventral digit patterning. The distribution of this condition with little fingers, clefting, and altered radial digit formation (PPD2 or radial longitudinal deficiency), as well as recent genetic and animal studies, suggests that dDD and altered dorsal-ventral patterning are linked to abnormal apical ectodermal ridge boundary formation. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic IV.

A Matched Comparative Study of the Bilhaut Procedure Versus Resection and Reconstruction for Treatment of Radial Polydactyly Types II and IV.

PURPOSE: To compare outcomes of the Bilhaut procedure with outcomes of conventional resection and reconstruction in radial polydactyly types II and IV. METHODS: Patients treated with the Bilhaut procedure were radiologically matched with patients treated with reconstruction. Evaluated outcomes included the Rotterdam assessment system, pinch strength, and thumb size measurements. To determine objectively which aesthetic outcome scores truly depended on surgical technique rather than observer opinion, we analyzed evaluations by a panel of 22 individuals with varying clinical experience who were blinded to the study protocol, using a linear mixed regression model. RESULTS: The Bilhaut procedure reduced the risk of suboptimal outcome for metacarpophalangeal joint instability in type IV radial polydactyly. Conversely, the Bilhaut procedure increased the risk of suboptimal scar appearance, residual prominence at amputation site, thumb size, and nail appearance. Tip pinch strength was more significantly reduced after the Bilhaut compared with reconstruction, whereas pulp circumference and nail width exceeded 100% of the unaffected contralateral hand after the Bilhaut reconstruction. There was no significant difference in active range of motion between procedures. Nail appearance proved the only aesthetic drawback of the Bilhaut procedure after adjustment for clinical experience. CONCLUSIONS: There was superior metacarpophalangeal joint stability after the Bilhaut procedure for radial polydactyly type IV, but this did not result in the presumed benefit to thumb strength. For experienced surgeons, both procedures resulted in comparable thumb active range of motion. However, aesthetic results were more likely perceived as pleasing after conventional reconstruction, even after adjusting for observer experience with regard to nail appearance. Despite possible benefits of modified Bilhaut procedures that preserve the nail, conventional reconstruction is the preferred procedure until otherwise proven. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic III.

Analysis of Sequelae after Pediatric Phalangeal Fractures.

INTRODUCTION: The majority of pediatric phalangeal fractures yield excellent results following conservative or operative treatment. However, a certain subset of fractures is associated with long-term sequelae such as osteonecrosis, physeal growth arrest, malunion, and malposition. PATIENTS AND METHODS: This study summarizes all sequelae following phalangeal fractures treated within a 10-year period (2003-2012). The underlying fractures were analyzed and classified in fractures with extensive soft tissue involvement, fractures involving the joint and adjacent bony parts, neck fractures, fractures complicated by infection and sequelae after simple fractures following inadequate initial treatment. RESULTS: In total, 40 patients (27 males; 13 females) with a mean age of 6.2 years (range, 1-18 years) were treated for sequelae following fractures of the phalanges. Ten patients (6 males; 4 females) developed sequelae (limited range of motion, premature physeal closure) following fractures with extensive soft tissue damage. Thirteen patients presented with sequelae (mostly limited range of motion, premature physeal closure) following fractures involving the joint and adjacent bony parts of the phalanges. Transcondylar and subcondylar neck fractures leading to sequelae were seen in 10 patients. Sequelae consisted of limited range of motion in nine and malposition in six cases. In half of the patients, osteonecrosis (n = 5) and premature physeal closure (n = 5) complicated the clinical course. Three patients with open fractures and four patients with inadequate initial treatment presented with sequelae. CONCLUSION: Most sequelae of phalangeal fractures are consequences of fracture per se and are therefore fateful. However, the degree and severity of the long-term sequelae can be minimized by a correct and timely treatment.

Defining Features of the Upper Extremity in Holt-Oram Syndrome.

PURPOSE: To investigate the distinguishing morphological characteristics of children with radial longitudinal deficiency (RLD) in Holt-Oram syndrome (HOS). METHODS: One hundred fourteen involved extremities in 62 patients with a diagnosis of HOS were identified at 3 institutions. Medical records and radiographs were evaluated. Radial longitudinal deficiency and thumb hypoplasia were classified according to the modified Bayne and Klug classification and Blauth classifications, respectively, when possible. Other unusual or distinguishing characteristics were catalogued. RESULTS: There was bilateral involvement in 84% of patients. The forearm was involved in 81% of the extremities and a shortened distal radius (Bayne and Klug type I RLD) was the most commonly identified forearm anomaly (40%). Radioulnar synostosis was present in 15% of the extremities, all in the proximal forearms with reduced radial heads. Thumb aplasia (Blauth type V hypoplastic thumb) was the most common type of classifiable thumb abnormality and occurred in 35% of involved thumbs. Twenty-seven percent of abnormal thumbs affected were not classifiable according to the Blauth classification, and 19% of involved thumbs (hypoplastic or absent) had first-web syndactyly. CONCLUSIONS: The upper extremity in HOS differs from the typical presentation of RLD. The forearm is more often involved and may demonstrate radioulnar synostosis. The thumb is frequently unclassifiable by the Blauth classification and has first-web syndactyly. The presence of radioulnar synostosis and syndactyly of the radial 2 digits in RLD should prompt the hand surgeon to obtain a cardiac evaluation and consider genetic testing for HOS. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic III.

A multicenter comparative study of two classification systems for radial polydactyly.

BACKGROUND: The aim of this study was to compare type occurrence and reliability of the Wassel and Rotterdam classifications for radial polydactyly. METHODS: The authors classified a large population of radial polydactyly patients from two European clinics using both classification systems, and compared the incidences of the different types to a population derived from a systematic literature review. The authors further assessed intraobserver and interobserver reliability of both classification systems in a test-retest design with seven observers, using kappa statistics. RESULTS: Forty percent of the 520 cases with available radiographs could not be classified using the Wassel classification, whereas all cases could be classified using the Rotterdam classification. All unclassifiable cases had aberrant components; the majority were of the triphalangeal (63 percent), deviating (43 percent), or hypoplastic (39 percent) kind. Types III, IV, and VI occurred more often when using the Rotterdam classification. Intraobserver and interobserver reliability was comparable for both classification systems (κ=0.87 versus κ=0.83, and κ=0.65 versus κ=0.70). Types II and IV had the lowest reliability in both the Wassel and Rotterdam classifications (κ=0.30 to 0.59). Aberrant components indicating deviation and hypoplasia had the lowest reliability in the Rotterdam classification (κ=0.19 to 0.45). CONCLUSIONS: The Rotterdam classification has broader classification possibilities and similar intraobserver and interobserver reliability compared with the Wassel classification. Although it is more complex and the aberrant components should be more strictly defined to increase its clinical relevance, we recommend using the Rotterdam classification. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, I.

Deletions of exons with regulatory activity at the DYNC1I1 locus are associated with split-hand/split-foot malformation: array CGH screening of 134 unrelated families.

BACKGROUND: A growing number of non-coding regulatory mutations are being identified in congenital disease. Very recently also some exons of protein coding genes have been identified to act as tissue specific enhancer elements and were therefore termed exonic enhancers or "eExons". METHODS: We screened a cohort of 134 unrelated families with split-hand/split-foot malformation (SHFM) with high resolution array CGH for CNVs with regulatory potential. RESULTS: In three families with an autosomal dominant non-syndromic SHFM phenotype we detected microdeletions encompassing the exonic enhancer (eExons) 15 and 17 of DYNC1I1. In a fourth family, who had hearing loss in addition to SHFM, we found a larger deletion of 510 kb including the eExons of DYNC1I1 and, in addition, the human brain enhancer hs1642. Exons 15 and 17 of DYNC1I1 are known to act as tissue specific limb enhancers of DLX5/6, two genes that have been shown to be associated with SHFM in mice. In our cohort of 134 unrelated families with SHFM, deletions of the eExons of DYNC1I1 account for approximately 3% of the cases, while 17p13.3 duplications were identified in 13% of the families, 10q24 duplications in 12%, and TP63 mutations were detected in 4%. CONCLUSIONS: We reduce the minimal critical region for SHFM1 to 78 kb. Hearing loss, however, appears to be associated with deletions of a more telomeric region encompassing the brain enhancer element hs1642. Thus, SHFM1 as well as hearing loss at the same locus are caused by deletion of regulatory elements. Deletions of the exons with regulatory potential of DYNC1I1 are an example of the emerging role of exonic enhancer elements and their implications in congenital malformation syndromes.

Duplications of BHLHA9 are associated with ectrodactyly and tibia hemimelia inherited in non-Mendelian fashion.

BACKGROUND: Split-hand/foot malformation (SHFM)-also known as ectrodactyly-is a congenital disorder characterised by severe malformations of the distal limbs affecting the central rays of hands and/or feet. A distinct entity termed SHFLD presents with SHFM and long bone deficiency. Mouse models suggest that a defect of the central apical ectodermal ridge leads to the phenotype. Although six different loci/mutations (SHFM1-6) have been associated with SHFM, the underlying cause in a large number of cases is still unresolved. METHODS: High resolution array comparative genomic hybridisation (CGH) was performed in patients with SHFLD to detect copy number changes. Candidate genes were further evaluated for expression and function during limb development by whole mount in situ hybridisation and morpholino knock-down experiments. RESULTS: Array CGH showed microduplications on chromosome 17p13.3, a locus previously associated with SHFLD. Detailed analysis of 17 families revealed that this copy number variation serves as a susceptibility factor for a highly variable phenotype with reduced penetrance, particularly in females. Compared to other known causes for SHFLD 17p duplications appear to be the most frequent cause of SHFLD. A ~11.8 kb minimal critical region was identified encompassing a single gene, BHLHA9, a putative basic loop helix transcription factor. Whole mount in situ hybridisation showed expression restricted to the limb bud mesenchyme underlying the apical ectodermal ridge in mouse and zebrafish embryos. Knock down of bhlha9 in zebrafish resulted in shortening of the pectoral fins. CONCLUSIONS: Genomic duplications encompassing BHLHA9 are associated with SHFLD and non-Mendelian inheritance characterised by a high degree of non-penetrance with sex bias. Knock-down of bhlha9 in zebrafish causes severe reduction defects of the pectoral fin, indicating a role for this gene in limb development.

Complex inheritance pattern resembling autosomal recessive inheritance involving a microdeletion in thrombocytopenia-absent radius syndrome.

Thrombocytopenia-absent radius (TAR) syndrome is characterized by hypomegakaryocytic thrombocytopenia and bilateral radial aplasia in the presence of both thumbs. Other frequent associations are congenital heart disease and a high incidence of cow's milk intolerance. Evidence for autosomal recessive inheritance comes from families with several affected individuals born to unaffected parents, but several other observations argue for a more complex pattern of inheritance. In this study, we describe a common interstitial microdeletion of 200 kb on chromosome 1q21.1 in all 30 investigated patients with TAR syndrome, detected by microarray-based comparative genomic hybridization. Analysis of the parents revealed that this deletion occurred de novo in 25% of affected individuals. Intriguingly, inheritance of the deletion along the maternal line as well as the paternal line was observed. The absence of this deletion in a cohort of control individuals argues for a specific role played by the microdeletion in the pathogenesis of TAR syndrome. We hypothesize that TAR syndrome is associated with a deletion on chromosome 1q21.1 but that the phenotype develops only in the presence of an additional as-yet-unknown modifier (mTAR).