Hereditary sensory and autonomic neuropathy type IV orthopaedic complications

A 5-Year-Old Palestinian Bedouin Girl with Repeated Self-Induced Injuries to the Digits, a Diagnosis of Congenital Insensitivity to Pain, and Anhidrosis

BACKGROUND Congenital insensitivity to pain with anhidrosis (CIPA), also referred to as hereditary sensory and autonomic neuropathy type IV, is a rare autosomal recessive disease caused by mutations in the NTRK1 gene. The inability to feel pain and temperature often leads to repeated severe and unintentional self-inflicted injuries; these can result in severe complications, as patients heal slowly from skin and bone injuries. This case report describes a 5-year-old Palestinian girl with self-inflicted injury to the digits, a dislocated distal inter-phalangeal joint of the left big toe, and a diagnosis of CIPA. CASE REPORT A 5-year-old girl, a daughter of related Palestinian Bedouin parents, presented with a chronic unhealed wound over the planter surface of the left foot. Painless repetitive minor traumata over the same area badly affected wound healing and this led to wound dehiscence and dislocation of the distal inter-phalangeal joint of the left big toe. Surgical fixation of the dislocated joint along with intravenous antibiotics and close follow-up resulted in eventual improvement and near complete wound healing despite the obviously slow healing process. The girl also displayed evidence of unintentional self-inflicted injury, which within the overall clinical context warranted a clinical suspicion of CIPA. This was confirmed by genetic testing for the presence of a homozygous frameshift mutation in the NTRK1 gene (c.1842_1843insT; p.Pro615Serfs*12). CONCLUSIONS This case report shows that a physician should have a low threshold of suspicion to investigate for CIPA when managing children with multiple unintentional self-inflicted injuries, anhidrosis, and pain insensitivity, mainly through genetic testing to detect mutations in the NTRK1 gene.

No pain, no gain? The effects of pain-promoting neuropeptides and neurotrophins on fracture healing

Neuropeptides and neurotrophins are key regulators of peripheral nociceptive nerves and contribute to the induction, sensitization, and maintenance of pain. It is now known that these peptides also regulate non-neuronal tissues, including bone. Here, we review the effects of numerous neuropeptides and neurotrophins on fracture healing. The neuropeptides calcitonin-gene related peptide (CGRP), substance P (SP), vasoactive intestinal peptide (VIP), and pituitary adenylate cyclase-activating peptide (PACAP) have varying effects on osteoclastic and osteoblastic activity. Ultimately, CGRP and SP both accelerate fracture healing, while VIP and PACAP seem to negatively impact healing. Unlike the aforementioned neuropeptides, the neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) have more uniform effects. Both factors upregulate osteoblastic activity, osteoclastic activity, and, in vivo, stimulate osteogenesis to promote fracture healing. Future research will need to clarify the exact mechanism by which the neuropeptides and neurotrophins influence fracture healing. Specifically, understanding the optimal expression patterns for these proteins in the fracture healing process may lead to therapies that can maximize their bone-healing capabilities and minimize their pain-promoting effects. Finally, further examination of protein-sequestering antibodies and/or small molecule agonists and antagonists may lead to new therapies that can decrease the rate of delayed union/nonunion outcomes and fracture-associated pain.

Hereditary sensory and autonomic neuropathies

Hereditary sensory and autonomic neuropathies (HSN/HSAN) are clinically and genetically heterogeneous disorders of the peripheral nervous system that predominantly affect the sensory and autonomic neurons. Hallmark features comprise not only prominent sensory signs and symptoms and ulcerative mutilations but also variable autonomic and motor disturbances. Autosomal dominant and autosomal recessive inheritance has been reported. Molecular genetics studies have identified disease-causing mutations in 11 genes. Some of the affected proteins have nerve-specific roles but underlying mechanisms have also been shown to involve sphingolipid metabolism, vesicular transport, structural integrity, and transcription regulation. Genetic and functional studies have substantially improved the understanding of the pathogenesis of the HSN/HSAN and will help to find preventive and causative therapies in the future.