Classification of dorsal and ventral dimelia in humans

My journey in hand surgery: combining patient care, clinical and basic science research

This review is about my clinical and research journey in hand surgery. The journey has been a worthwhile and meaningful one, especially when I felt there were areas I could influence management, whether this be rare cases, common conditions or where a suggested algorithm may be helpful. I also had the unique privilege of working with geneticists, which has resulted in clinical-pathological publications that could influence patient management, as shared from a clinician's perspective. It is hoped this article will inspire young clinician scientists to pursue a journey of collaboration with other researchers.

A classification system for split-hand/ foot malformation (SHFM): A proposal based on 3 pedigrees with WNT10B mutations

SHFM6 (OMIM 225300) is caused by WNT10B pathogenic variants (12q13.12). It is one of the rarest forms of SHFM; with only seven pathogenic variants described in the world literature. Furthermore, it has not been determined if SHFM6 has specific phenotypic characteristics. In this paper, we present a case series of three unrelated families with SHFM6 caused by three novel WNT10B pathogenic variants. The index patient of the first family was homozygous for the nonsense variant c.676C > T (p.Arg226*) in the WNT10B gene. The index case of the second family had a homozygous splice variant c.338-1G > C in the WNT10B gene. Finally, the index case of the third family carried two different variants in the WNT10B gene: A nonsense variant (p.Arg226*), and a missense variant (p.Gln86Pro). The latter represents the first compound heterozygous pathogenic variant related to SHFM6. We also offer a classification system for the hand/foot defects to illustrate the specific phenotypic characteristics of SHFM6. Based on this classification and a review of all previously reported cases, we demonstrate that SHFM6 caused by WNT10B pathogenic variants have the following characteristics: more severe feet defects (compared to the hand defects), polydactyly, severe flexion digital contractures, and phalangeal dysplasia.

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.

Dorsal and Ventral Dimelia in the Same Hand in A Patient with Severe Ulnar Ray Deficiency: A Case Report

Dorsal dimelia (the appearance of dorsal hand structures on the palmar aspect of the hand) and ventral dimelia (the appearance of ventral hand structures on the dorsal aspect of the hand) are rare congenital anomalies of the hand. None of the previously reported cases had combined dorsal and ventral dimelia in the same patient. Here, we report a case of severe ulnar ray deficiency. The hand had two digits: the radial digit had a palmar nail (dorsal dimelia) and the ulnar digit had absence of the normal dorsal nail along with the appearance of an ectopic pulp on the dorsal aspect of the digit (ventral dimelia). Ulnar ray deficiency is an error of sonic hedgehog (SHH) responsible for antero-posterior patterning of the limb in-utero. Ventral and dorsal dimelia are errors of dorso-ventral patterning of the hand. The complex interactions of SHH with the dorso-ventral axis of development may explain the concurrent dimelia in our patient.

A Review of the Genetics and Pathogenesis of Syndactyly in Humans and Experimental Animals: A 3-Step Pathway of Pathogenesis

Embryology of normal web space creation and the genetics of syndactyly in humans and experimental animals are well described in the literature. In this review, the author offers a 3-step pathway of pathogenesis for syndactyly. The first step is initiated either by the overactivation of the WNT canonical pathway or the suppression of the Bone Morphogenetic Protein (BMP) canonical pathway. This leads to an overexpression of Fibroblast Growth Factor 8 (FGF8). The final step is the suppression of retinoic acid in the interdigital mesenchyme leading to suppression of both apoptosis and extracellular matrix (ECM) degradation, resulting in syndactyly.

Classification of congenital upper limb anomalies: towards improved communication, diagnosis, and discovery

Recently the International Federation of Societies for Surgery of the Hand replaced the Swanson scheme for classifying congenital upper limb anomalies with the Oberg, Manske, Tonkin (OMT) classification. This review explores the reasons for this change after nearly 50 years of using the Swanson classification. In particular, it documents the state of our understanding regarding genetics and limb development at the time Swanson generated his classification. It also describes the continued progress in clinical genetics and developmental biology. Such progress drives the need to embrace and incorporate these changes within a new classification scheme; one that will improve communication, diagnosis, and support further discovery of the pathogenesis of congenital hand anomalies.

Radiographic assessment of congenital malformations of the upper extremity

Congenital and developmental malformations of the upper extremity are uncommon and their diagnosis can challenge radiologists. Many complex classification systems exist, the latest of which accounts for the complex embryology and pathogenetic mechanisms that govern the formation of these anomalies. Using appropriate descriptors allows for more specific diagnosis and improved consultation with referring pediatricians and surgeons, helping to guide medical and surgical interventions and, if indicated, further investigation for associated abnormalities and underlying syndromes. We review the imaging characteristics of upper limb malformations to help pediatric radiologists better understand the classification and workup necessary in these cases.

The Classification of Swanson for Congenital Anomalies of Upper Limb Modified by the Japanese Society for Surgery of the Hand (JSSH)

The aim of this study is to introduce the classification of Swanson for congenital anomalies of upper limb modified by the Japanese Society for Surgery of the Hand (the JSSH modification) in English. The Swanson classification has been widely accepted by most hand surgeons. However, several authors have suggested that complex cases, particularly those involving the complex spectrum of cleft hand and symbrachydactyly, are difficult to classify into the classification schemes. In the JSSH modification, brachysyndactyly, so-called atypical cleft hand and transverse deficiency are included under the same concept of transverse deficiency. Cleft hand, central polydactyly, and syndactyly are included in the same category of abnormal induction of digital rays. We believe that the JSSH modification system is effective in providing hand surgeons with the clinical features and conditions for congenital anomalies.

Concurrent dorsal dimelia in 160 consecutive patients with congenital anomalies of the hands and feet

This study was designed to investigate the prevalence of dorsal dimelia in a series of 160 consecutive patients with congenital anomalies of the hands and feet, and to investigate the distribution of dorsal dimelia and the concurrent anomalies. Five cases (3.1%) showed evidence of dorsal dimelia and the distribution of dorsal dimelia was similar to the distribution of concurrent anomalies in all five cases. Another 11 cases of concurrent dorsal dimelia with other congenital anomalies have been reported previously with a positive match in the distributions in all cases. This similarity in the distribution in all 16 reported cases (including the five cases in the current study) is statistically significant. It is concluded that dorsal dimelia in humans is not as rare as it is generally thought to be, and that it may be viewed as an error of dorso-ventral patterning, which occurs in the same distribution as other concurrent anomalies.