Video 1
Neurological Examination: Initial visit and 3-Year Follow-up. This video demonstrates mild, medium-to-high frequency postural tremors affecting the distal joints of both hands, observed during both the initial visit and the 3-year follow-up. Spooning is present in both hands when the arms are extended forward, with the left hand showing a more pronounced effect in the wing-beat position. Additionally, there is a clear indication of dystonic flexion in the right fifth finger during the wing-beat position. Extremely mild tremors were observed on the left hand during the spiral drawing test. The nose-finger-nose test is negative, suggesting the absence of kinetic tremor.
Figure 1
T1-weighted transverse magnetic resonance images of the patient’s arms (A–B) and thighs (C–D). Mild fatty infiltration of the deltoid muscle and triceps brachii was observed in the upper arms. Mild-to-moderate fatty infiltration was observed in the biceps femoris, quadriceps femoris, sartorius, semitendinosus, semimembranosus, and gracilis muscles.
Figure 2
Muscle biopsy from patient’s brachial biceps conducted at 21 years of age. (A) Mild fiber size variation is detectable (H&E). (B–C) ATPase staining of serial sections at different pH levels: (B) ATPase pH 4.2; and (C) ATPase pH 4.5. These figures illustrate three different fiber types. Black staining corresponds to type 1 fibers. In both figures B and C, grayish-white staining corresponds to Type 2 A fibers. In figure B, grayish-white staining also indicates Type 2B fibers, whereas in figure C, Type 2B fibers are indicated by dark gray staining. Within the observed field of view, only one small type 2 A fiber was observed (indicated by an arrow). (D) Nemaline rod or rod-like structures, filamentous tangles, ragged red fibers, or rimmed vacuoles were not observable via modified Gomori trichrome staining. (E) With nicotinamide adenine dinucleotide dehydrogenase-tetrazolium reductase (NADH-TR) staining, the intermyofibrillar network was slightly disturbed. Scale bar, 100 μm.
Figure 3
Family pedigree and sequence chromatograms of MYH2 variants. The localization of variants is indicated by arrows. Squares, males; circles, females. The filled symbols and those with central dots represent the affected individuals and variants carriers, respectively. The genotypes of each family member in the MYH2 are shown. +, mutant allele; –, wild-type allele. The thick arrow indicates the proband. Identification of two variants in the MYH2 gene in the proband. First, the heterozygous c.3565 del C variant, which was inherited from the father. The second variant is a heterozygous c.505 + 2T>C splice site variant, which was inherited from the unaffected mother.