Symmetrical atrophy of the peroneal muscle gradually progresses upward

Introduction Peronial myoatrophy, also known as Charcot-Marie-Tooth disease (CMT), is the most common group of peripheral neuropathies, accounting for approximately 90% of all hereditary neuropathies. The common features of this group of diseases are the onset of children or adolescents, chronic progressive sacral muscle atrophy, and the symptoms and signs are relatively symmetrical. Most patients have a family history. Because of the main clinical features of iliac muscle atrophy, it is also known as peroneal myoatrophy. According to neurophysiological and neuropathological findings, CMT is classified into type I and type II, CMTI type is called hypertrophic type, and type CMTII is called neuronal type. The progressive development of the symmetry atrophy of the sacral muscle is a clinical manifestation of the disease.

Cause

(1) Causes of the disease

The disease is mainly caused by genetic factors, CMT1 type, CMT2 type are autosomal dominant inheritance, there may be scattered cases.

The pathogenic gene of 1CMT1A is located at 17p11.2-12, and the nuclear gene encodes peripheral neuromyelin protein 22 (PMP22). Repeated mutation of PMP22 gene leads to overexpression, which increases PMP22 protein. A small number of patients produce abnormal PMP22 protein due to PMP22 gene mutation. And cause illness.

2CMT2 type: CMT2A gene is located on chromosome 1p35-36, CMT2B is located at 3q13-22, CMT2C is located at 5q, CMT2D is located at 7p14, and CMT2E is located at 8p21. CMT also has an X-linked dominant (CMTX) chromosomal recessive (CMT4) approach.

(two) pathogenesis

Genetic mode

(1) CMTI type: it can be autosomal dominant, recessive and X-linked dominant or recessive. Recent studies have shown that CMTI types are divided into IA type, IB type and IC type. The most common type of CMTIA (56% to 60%) is caused by mutation of the PMP-22 gene on autosomal 17P11.2-12. The CMTIB type is rare (30%), and the pathological gene is involved in Iq21-23, which is associated with mutation of the myelin protein P0 (MPZ) gene. The pathological genes of the IC type are still unknown. The X-linked pathological gene is at Xq13-1.

(2) CMTII type: There are three types of inheritance, usually autosomal dominant, recessive and X-linked inheritance. The disease often stains the dominant pathological gene at Ip35-36. Changyin and X-linked pathological genes are unknown.

2. Pathological changes

(1) CMTI type: The results of CMTI-type sural nerve biopsy showed that the number of major large and medium-diameter fibers was significantly reduced, and collagen in the bundle was proliferated. With age, the density of myelinated fibers is progressively reduced, and demyelination is aggravated. Due to the enhanced segmental demyelination and remyelination process, Schwann cell proliferation and neuroendosome components form a concentric "onion ball"-like structure around the axon. Spinal cord degeneration, in which the thin bundle is more pronounced than the wedge bundle.

(2) CMT type II: CMT type II sural nerve pathology is mainly axonal degeneration, demyelinating is not significant, Schwann cell proliferation is "onion ball" change and rare.

an examination

Related inspection

Electromyography toe long extensor muscle strength test

Clinical manifestation

Often in children or adolescent insidious onset. More men than women, progress is slow. In most patients, muscle atrophy and muscle weakness begin from the distal muscles of the lower extremities (sacral muscles, total toe muscles, and small muscles of the feet), gradually developing upwards and being symmetrical. A small number of patients can also start from the hand. Muscle atrophy often has obvious boundaries, and the lower limbs do not exceed the lower third of the thigh, which resembles an "inverted bottle" (called "tiger leg"). Due to muscle atrophy, arched foot, foot drop and horseshoe varus deformity may occur, but the muscle strength is still relatively good, and is not proportional to muscle atrophy. Upper limb muscle atrophy begins with small muscles in the hand, but usually does not exceed the lower third of the forearm. The quadriplegia reflexes weakened or disappeared, and the Achilles tendon reflexes disappeared more often. There may be four limb-type sensory disturbances, accompanied by autonomic dysfunction such as rough skin, cold extremities, less sweat or cyanosis, and occasional changes in optic atrophy, retinal degeneration and nystagmus.

Differential diagnosis

The disease mainly needs to be identified with the following diseases:

1. Distal muscular dystrophy: The muscle weakness and muscle atrophy gradually develop in the distal extremities of the extremities. The adult onset, myogenic damage, electromyography, and normal NCV can be identified.

2. Chronic progressive distal spinal muscular atrophy: The muscle atrophy and muscle weakness of the disease and the course of the disease are similar to CMT, but the sensory function is not tired, and EMG shows anterior horn damage.

3, hereditary ataxia with muscular atrophy: also known as Roussy-Lévy syndrome, childhood onset, slow progression, manifestation of sacral muscle atrophy, arched foot, scoliosis, quadriplegia tendon reflex or disappear, motor NCV slow However, there are ataxia, gait, hand tremor and other ataxia performances.

The material in this site is intended to be of general informational use and is not intended to constitute medical advice, probable diagnosis, or recommended treatments.