Classically, weakness develops in the face, then the shoulder girdle, then the upper arm. These muscles can be spared and other muscles usually are affected. The order of muscle involvement can cause the appearance of weakness "descending" from the face to the legs. Distribution and degree of muscle weakness is extremely variable, even between identical twins. Musculoskeletal pain is very common, most often described in the neck, shoulders, lower back, and the back of the knee. Muscle weakness usually becomes noticeable on one side of the body before the other, a hallmark of the disease. The right shoulder and arm muscles are more often affected than the left upper extremity muscles, independent of handedness. Otherwise, muscle involvement is equally common on both sides. Classically, symptoms appear in those 15 – 30 years of age, although infantile onset, adult onset, and absence of symptoms despite having the causal genetics also occur.<unk> 1 with a very large D4Z4 deletion (EcoRI 10-11 kb) is more strongly associated with infantile onset and severe weakness. On average,<unk> 2 presents 10 year later than<unk> 1. Otherwise,<unk> 1 and<unk> 2 are indistinguishable on the basis of weakness. Disease progression is slow, and long static phases, in which no progression is apparent, is not uncommon. Less commonly, individual muscles rapidly deteriorate over several months. Face Weakness of the muscles of the face is the most distinguishing sign of<unk> . It is typically the earliest sign, although it is rarely the initial complaint. At least mild facial weakness can be found in 90% or more with<unk> . One of the most common deficits is inability to close the eyelids, which can result in sleeping with the eyelids open and dry eyes. The implicated muscle is the orbicularis oculi muscle. Another common deficit is inability to purse the lips, causing inability to pucker, whistle, or blow up a balloon. The implicated muscle is the orbicularis oris muscle. A third common deficit is inability raise the corners of the mouth, causing a "horizontal smile," which looks more like a grin. Responsible is the zygomaticus major muscle. Weakness of various facial muscles contributes to difficulty pronouncing the letters M, B, and P. Facial expressions can appear diminished, arrogant, grumpy, or fatigued. Muscles used for chewing and moving the eyes are not affected. Difficulty swallowing is not typical, although can occur in advanced cases.<unk>  is generally progressive, but it is not established whether facial weakness is progressive or stable throughout life. Shoulder and chest Bilateral scapular winging, right moreso than left. Left image showing wall push test, right image showing attempted shoulder flexion. After the facial weakness, weakness usually develops in the muscles of the chest and those that span from scapula to thorax. Symptoms involving the shoulder, such as difficulty working with the arms overhead, are the initial complaint in 80% of cases. Predominantly, the serratus anterior and middle and lower trapezii muscles are affected; the upper trapezius is often spared. Trapezius weakness causes the scapulas to become downwardly rotated and protracted, resulting in winged scapulas, horizontal clavicles, and sloping shoulders; arm abduction is impaired. Serratus anterior weaknesss impairs arm flexion, and worsening of winging can be demonstrated when pushing against a wall. Severe muscle wasting can make bones and spared shoulder muscles very visible, a characteristic example being the "poly-hill" sign elicited by arm elevation. The first "hill" or bump is the upper corner of scapula appearing to "herniate" up and over the rib cage. The second hill is the AC joint, seen between a wasted upper trapezius and wasted upper deltoid. The third hill is the lower deltoid, distinguishable between the wasted upper deltoid and wasted humeral muscles. Shoulder weakness and pain can in turn lead to shoulder instability, such as recurrent dislocation, subluxation, or downward translation of the humeral head. Also affected is the chest, particularly the parts of the pectoralis major muscle that connect to the sternum and ribs. The part that connects to the clavicle is less often affected. This muscle wasting pattern can contribute to a prominent horizontal anterior axillary fold. Muscles spanning from the scapula to the arm are generally spared, which include deltoid and the rotator cuff muscles. The deltoid can be affected later on, especially the upper portion. Beyond this point the disease does not progress further in 30% of familial cases. Upper arm and lower body After facial and upper torso weakness, weakness can "descend" to the upper arms (biceps muscle and triceps muscle) and the pelvic girdle. The forearms are usually spared, resulting in an appearance some compare to the fictional character Popeye. Sometimes, the weakness is observed to "skip" the pelvis and involve the tibialis anterior (shin muscle), causing foot drop. Weakness can also occur in the abdominal muscles, which can manifest as a protuberant abdomen, lumbar hyperlordosis, the inability to do a sit-up, or the inability to turn from one side to the other while lying down. Of the rectus abdominis muscle, the lower portion is preferentially affected, manifesting as a positive Beevor's sign. Weakness in the legs can manifest as difficulty walking or hips held in slight flexion. Non-muscular Funduscopy of the retinal: (A) normal blood vessels (B) tortuous blood vessels, as often seen with<unk>  The most common non-musculoskeletal manifestation of<unk>  is abnormalities in the small arteries (arterioles) in the retina. Tortuosity of the arterioles is seen in approximately 50% of those with<unk> . Less common arteriole abnormalities include telangiectasias and microaneurysms. These abnormalities of arterioles usually do not affect vision or health, although a severe form of it mimics Coat's disease, a condition found in about 1% of<unk>  cases and more frequently associated with large 4q35 deletions. High-frequency hearing loss can occur in those with large 4q35 deletions, but otherwise is no more common compared to the general population. Large 4q35 deletion can lead to various other rare manifestations. Scoliosis can occur, thought to result from weakness of abdominal, hip extensor, and spinal muscles. Conversely, scoliosis can be viewed as a compensatory mechanism to weakness. Breathing can be affected, associated with kyphoscoliosis and wheelchair use; it is seen in one-third of wheelchair-bound patients. However, ventilator support (nocturnal or diurnal) is needed in only 1% of cases. Although there are reports of increased risk of cardiac arrhythmias, general consensus is that the heart is not affected.
Facioscapulohumeral muscular dystrophy
Limb–girdle muscular dystrophy
Becker muscular dystrophy
Ullrich congenital muscular dystrophy
Fukuyama congenital muscular dystrophy
Spinal muscular atrophy
Duchenne muscular dystrophy
Jokela type spinal muscular atrophy