PMC10200208_01
Axial T1-weighted muscle magnetic resonance imaging. (A) The tongue muscle tissue is replaced by fat (arrows), whereas other neck muscles are preserved. (B-D) The upper-arm, trunk, and hip region show no obvious muscle atrophy or fat replacement. (E) Bilateral adductor magnus muscle atrophy with fat replacement is observed at the thigh level (arrows). (F) The lower leg level shows bilateral soleus muscle fat replacement (arrows).
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Axial T1-weighted magnetic resonance imaging revealed selective skeletal muscle fat replacement involving the tongue, bilateral adductor magnus, and soleus; along with bilateral adductor magnus muscle atrophy (Fig. 1A, E, F, arrow). In contrast, other truncal and limb muscles were preserved (Fig. 1B-F).
Biopsy sample of the left rectus femoris. (A) Variable myofiber size and the absence of inflammatory cells, necrotic fibers, or regenerating fibers are observed on H&E. (B) On modified Gomori trichrome staining, rimmed vacuoles are observed in only one fiber (arrow). (C) Intracytoplasmic accumulation of p62 aggregates are observed in only one fiber (arrow), along with some p62-positive intranuclear inclusions on immunohistochemistry (arrowheads). (D) Nuclear accumulation of insoluble PABPN1 is highlighted by anti-PABPN1 antibody in immunohistochemistry (arrows). Scale bars: 100mum.
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Biopsy of the left rectus femoris muscle showed nonspecific myopathic change with fiber size variation on routine hematoxylin and eosin (H&E) staining, and with no inflammatory cells, necrotic fibers, or regenerating fibers (Fig. 2A). Modified Gomori trichrome staining showed rimmed vacuoles in only one fiber (Fig. 2B, arrow). The p62 immunohistochemistry study showed cytoplasmic accumulation of p62 aggregates in only one fiber (Fig. 2C, arrow) and some p62-positive intramyonuclear inclusions (Fig. 2C, arrowheads). The immunohistochemistry study for anti-PABPN1 antibody revealed nuclear accumulation of insoluble PABPN1, which corresponds to the p62-positive intramyonuclear inclusions (Fig. 2D).
DNA sequence analysis. (A) The upper panel reports the sequence trace of the patient, indicating the position of the c.34G > T base change (arrow). The lower panel reports the coding sequence of the first 18 codons in exon 1 of the PABPN1 gene of the patient. The c.34G > T mutation results in the substitution of glycine by tryptophan at codon 12, which does not cause expansion of polyalanine stretch. (B) The coding sequence of the 4 reported cases with the c.35G > C mutation. The c.35G > C mutation results in the substitution of glycine by alanine at codon 12, which generates a sequence of 13 contiguous alanines.
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Gly12Trp), in exon 1 of the PABPN1 gene (Fig. 3A).