Overgrowth of the Hand and Upper Extremity and Associated Syndromes

Surgical management of adult hand macrodactyly in a 49-year-old patient: A case report

BACKGROUND

Macrodactyly is a rare congenital malformation characterized by an increase in the size of all structures of a digit, accounting for less than 1% of all congenital upper extremity conditions.

CASE SUMMARY

We report a case involving a 49-year-old woman who presented for the first time with untreated, radial-sided hand macrodactyly. We performed soft tissue debulking, amputation, median nerve neurotomy and coaptation, and carpal tunnel release. At the 6-year follow-up, no significant growth was observed in the bone or soft tissue of the affected area.

CONCLUSION

Tissue overgrowth in patients with progressive macrodactyly can continue and progress excessively with age. Median nerve neurotomy and coaptation play a crucial role in preventing recurrence of the deformity.

Genotypes and phenotypes heterogeneity in PIK3CA-related overgrowth spectrum and overlapping conditions: 150 novel patients and systematic review of 1007 patients with PIK3CA pathogenetic variants

BACKGROUND

Postzygotic activating PIK3CA variants cause several phenotypes within the PIK3CA-related overgrowth spectrum (PROS). Variant strength, mosaicism level, specific tissue involvement and overlapping disorders are responsible for disease heterogeneity. We explored these factors in 150 novel patients and in an expanded cohort of 1007 PIK3CA-mutated patients, analysing our new data with previous literature to give a comprehensive picture.

METHODS

We performed ultradeep targeted next-generation sequencing (NGS) on DNA from skin biopsy, buccal swab or blood using a panel including phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin pathway genes and GNAQ, GNA11, RASA1 and TEK. Additionally, 914 patients previously reported were systematically reviewed.

RESULTS

93 of our 150 patients had PIK3CA pathogenetic variants. The merged PROS cohort showed that PIK3CA variants span thorough all gene domains, some were exclusively associated with specific PROS phenotypes: weakly activating variants were associated with central nervous system (CNS) involvement, and strongly activating variants with extra-CNS phenotypes. Among the 57 with a wild-type PIK3CA allele, 11 patients with overgrowth and vascular malformations overlapping PROS had variants in GNAQ, GNA11, RASA1 or TEK.

CONCLUSION

We confirm that (1) molecular diagnostic yield increases when multiple tissues are tested and by enriching NGS panels with genes of overlapping 'vascular' phenotypes; (2) strongly activating PIK3CA variants are found in affected tissue, rarely in blood: conversely, weakly activating mutations more common in blood; (3) weakly activating variants correlate with CNS involvement, strong variants are more common in cases without; (4) patients with vascular malformations overlapping those of PROS can harbour variants in genes other than PIK3CA.

Lateralized and Segmental Overgrowth in Children

Congenital disorders of lateralized or segmental overgrowth (LO) are heterogeneous conditions with increased tissue growth in a body region. LO can affect every region, be localized or extensive, involve one or several embryonic tissues, showing variable severity, from mild forms with minor body asymmetry to severe ones with progressive tissue growth and related relevant complications. Recently, next-generation sequencing approaches have increased the knowledge on the molecular defects in LO, allowing classifying them based on the deranged cellular signaling pathway. LO is caused by either genetic or epigenetic somatic anomalies affecting cell proliferation. Most LOs are classifiable in the Beckwith-Wiedemann spectrum (BWSp), PI3KCA/AKT-related overgrowth spectrum (PROS/AROS), mosaic RASopathies, PTEN Hamartoma Tumor Syndrome, mosaic activating variants in angiogenesis pathways, and isolated LO (ILO). These disorders overlap over common phenotypes, making their appraisal and distinction challenging. The latter is crucial, as specific management strategies are key: some LO is associated with increased cancer risk making imperative tumor screening since childhood. Interestingly, some LO shares molecular mechanisms with cancer: recent advances in tumor biological pathway druggability and growth downregulation offer new avenues for the treatment of the most severe and complicated LO.

Neural control of growth and size in the axolotl limb regenerate

The mechanisms that regulate growth and size of the regenerating limb in tetrapods such as the Mexican axolotl are unknown. Upon the completion of the developmental stages of regeneration, when the regenerative organ known as the blastema completes patterning and differentiation, the limb regenerate is proportionally small in size. It then undergoes a phase of regeneration that we have called the ‘tiny-limb’ stage, which is defined by rapid growth until the regenerate reaches the proportionally appropriate size. In the current study we have characterized this growth and have found that signaling from the limb nerves is required for its maintenance. Using the regenerative assay known as the accessory limb model (ALM), we have found that growth and size of the limb positively correlates with nerve abundance. We have additionally developed a new regenerative assay called the neural modified-ALM (NM-ALM), which decouples the source of the nerves from the regenerating host environment. Using the NM-ALM we discovered that non-neural extrinsic factors from differently sized host animals do not play a prominent role in determining the size of the regenerating limb. We have also discovered that the regulation of limb size is not autonomously regulated by the limb nerves. Together, these observations show that the limb nerves provide essential cues to regulate ontogenetic allometric growth and the final size of the regenerating limb.

Humans’ ability to regrow lost or damaged body parts is relatively limited, but some animals, such as the axolotl (a Mexican salamander), can regenerate complex body parts, like legs, many times over their lives. Studying regeneration in these animals could help researchers enhance humans’ abilities to heal. One way to do this is using the Accessory Limb Model (ALM), where scientists wound an axolotl’s leg, and study the additional leg that grows from the wound.

The first stage of limb regeneration creates a new leg that has the right structure and shape. The new leg is very small so the next phase involves growing the leg until its size matches the rest of the animal. This phase must be controlled so that the limb stops growing when it reaches the right size, but how this regulation works is unclear. Previous research suggests that the number of nerves in the new leg could be important.

Wells et al. used a ALM to study how the size of regenerating limbs is controlled. They found that changing the number of nerves connected to the new leg altered its size, with more nerves leading to a larger leg. Next, Wells et al. created a system that used transplanted nerve bundles of different sizes to grow new legs in different sized axolotls. This showed that the size of the resulting leg is controlled by the number of nerves connecting it to the CNS. Wells et al. also showed that nerves can only control regeneration if they remain connected to the central nervous system.

These results explain how size is controlled during limb regeneration in axolotls, highlighting the fact that regrowth is directly controlled by the number of nerves connected to a regenerating leg. Much more work is needed to reveal the details of this process and the signals nerves use to control growth. It will also be important to determine whether this control system is exclusive to axolotls, or whether other animals also use it.

A Review of Multiple Venous Malformations of the Upper Limb: Classification, Genetics, and Pathogenesis

Venous (cavernous) malformations are commonly seen in the upper limb. There is no consensus in the literature regarding the classification of venous malformations. Patients may be viewed as 2 clinical entities: patients with single or multiple lesions. Single venous malformations are sporadic and nonsyndromic, whereas the presence of multiple malformations indicates the presence of either an inherited or an overgrowth (noninherited) disorder. In this article, the author reviews multiple venous malformations of the upper limb, offers a novel classification, and describes their clinical entities along with their genetics and pathogenesis. These clinical entities will also be described by categorizing the cases as per the clinical presentation. Furthermore, the number of cases seen by the author (during an experience of 28 years of practice in Saudi Arabia) in each category will be reviewed to give the reader an overall view of the frequency of presentation of each category to the hand/plastic surgery clinic. Clinically, patients may present in 4 different presentations depending on the distribution of the lesions: the late-onset malformations confined to the upper limb; malformations involving the limbs/face/trunk with no mucosal lesions; widespread malformations of the skin, oral mucosa, and the intestine; and venous malformations presenting as a well-known syndrome. The author has seen a total of 84 patients, and the most 2 common presentations were late-onset type (n = 26) and malformations involving the limbs/face/trunk with no mucosal lesions (n = 36). This is the most comprehensive review of multiple venous malformations of the upper limb.

Macrodactyly of the foot resulting from plantar nerve impairment

The role of the plantar nerve in the pathogenesis of macrodactyly of the foot is unknown. We investigated the distribution of affected toes and forefoot in 27 feet of 26 patients with pedal macrodactyly, and how this relates to innervation of the affected plantar nerve. A preoperative ultrasound examination was performed to determine the diameter and structure of the plantar nerve. Histologic findings were recorded during surgery. The microstructure of affected plantar nerves was evaluated by hematoxylin-eosin staining, while S100 expression was assessed by immunofluorescence analysis. Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) gene mutation in the affected nerve tissue was detected by Sanger DNA sequencing. The affected toes and forefoot involved innervation of the medial plantar nerve in 25/27 feet, the lateral plantar nerve in one foot, and both medial and lateral plantar nerves in one foot. All affected plantar nerves, which were accompanied by a fatty strip, were surrounded by or infiltrated with fat. The affected plantar nerves showed enlargement, a tortuous course, fatty infiltration, or a combination of these. Pathologic changes in affected plantar nerves involved only the epineurium and not the perineurium or endoneurium. Expression of the Schwann cell marker S100 was absent in some areas of affected nerves. Sequencing of PIK3CA exons identified a gain-of-function mutation (p.His1047Arg) in affected plantar nerves. These results indicate that pathologic impairment of the plantar nerve can lead to macrodactyly of the foot, which may be considered as a nerve trunk disease.

Late-onset multiple venous malformations confined to the upper limb: link to somatic MAP3K3 mutations

Venous (cavernous) malformations are commonly seen in the upper limb. Almost all venous malformations are congenital. They may be sporadic, familial, or syndromic. Late-onset, multiple venous malformations confined to the upper limb are rare. Lesions present after puberty. All previously reported cases were located subcutaneously and were small in size. The condition is non-hereditary and non-syndromic. We present a unique series of eight patients with this rare condition. Unique features included the presence of large malformations (up to 20 cm in diameter) and the presence of subfascial lesions causing nerve compression. Surgical excision was curative. Mutational analysis in one patient identified a novel somatic MAP3K3 gene mutation (c.1723T > C, p.Tyr 575 His) in the affected veins. The encoded MAP3K3 protein is known to accelerate the RAS pathway of cellular proliferation.Level of evidence: IV.

Macrodactyly: decision-making and surgery timing

Macrodactyly is a rare condition in which fingers, hands or limb growth is unregulated, resulting in overgrowth of tissues in the affected extremities. It is critical to properly assess these extremities for signalling pathway, psychological impact and potential surgical intervention, to achieve the best possible outcome for each patient. Treatment approaches can vary, and patient and family expectations weigh heavily on care complexity. Common surgical procedures may include epiphysiodeses, osteotomies, debulking procedures, carpal tunnel releases, toe transfers and amputations. The selection and timing of these surgeries is a vital component of the approach, as delayed healing and excessive scarring may occur. The purpose of this review is to assist in the navigation of decision-making and surgical timing for patients presenting with overgrowth manifesting itself as macrodactyly.

Treatment of Hand Macrodactyly With Resection and Toe Transfers

Macrodactyly is an uncommon congenital hand condition that can be difficult to treat and that can have a profound negative impact on patients and their families. Although many treatments have been described, results tend to be inconsistent. The authors report a case in which a combination of ray resection, partial finger resection, and toe transfer resulted in a 4-digit hand with acceptable function and cosmesis.