Fig. 6

Muscle imaging in treatable and potentially treatable diseases with grading (Wattjes et al. 2010) diagrams of LGMD R28 (a, b, and c), Late onset Pompe disease (d, e, and f), Late onset TK2d (g, h, and i), and POLG deficiency (j, k, and l). Muscle MRI of anti-NXP2/anti-PL7 subacute dermatomyositis (m, n, o, p, q, and r). Muscle MRI of anti-Mi-2 beta chronic dermatomyositis (s, t, u, v, w, and x) of the pelvis (a, d, g, j, m, p, s, and v), thighs (b, e, h, k, n, q, t, and w), and legs (c, f, i, l, o, r, u, and x). LGMD R28 HMGCR treatable with mevalonate (Morales-Rosado et al. 2023 and Yogev et al. 2023). (a, b, and c) *Diagrams were prepared based on photographs of the thighs and legs by Morales-Rosado et al. 2023 and Yogev et al. 2023b Thighs with almost complete muscle fat replacement of all compartments. c Legs with severe muscle fat replacement of gastrocnemius medialis, gastrocnemius lateralis, and soleus. Late onset Pompe disease treatable with enzyme replacement (d, e, and f) (Díaz‐Manera et al. 2021) d Pelvis with severe muscle fat replacement of gluteus medius, and gluteus minimus, with moderate involvement of gluteus maximus. e Thighs with severe muscle fat replacement of adductor magnus and biceps femoris long head, moderate involvement of vastus intermedius, semitendinosus, and semimembranosus, with mild involvement of vastus lateralis, and vastus medialis. f Legs with almost invariable complete preservation of all compartments that in some patients may present mild involvement of gastrocnemius medialis, and soleus. Late onset TK2 deficiency (TK2d) potentially treatable with thymidine and deoxycytidine nucleosides that frequently presents a peculiar combination of facial (with or without ptosis and/or ophthalmoparesis), cervical and axial weakness, with early respiratory insufficiency (g, h, and i) (Domínguez-González et al. 2022). g Pelvis with severe muscle fat replacement of gluteus maximus. h Thighs with severe muscle fat replacement of sartorius and diffuse moth eaten pattern (hachurated graticule) of moderate muscle fat replacement involving gracilis, biceps femoris long head, semitendinosus, and semimembranosus. i Legs with severe muscle fat replacement of gastrocnemius medialis. POLG deficiency (j, k, and l) is nowadays nontreatable but it is potentially treatable with deoxyribonucleoside (Pitceathly et al. 2013; Tasca et al. 2017; Kristiansen et al. 2023). Diagrams based on photographs by Pitceathly et al. 2013, and Tasca et al. 2017. j Pelvis with preservation of glutei muscles. k Thighs with concentric involvement characterized by severe muscle fat replacement from the outer, subcutaneous layers and progresses to the inner profound layers moving distally; there is severe involvement of vastus lateralis, rectus femoris, outer layer of lateral part of vastus intermedius, sartorius, gracilis, outer layer of biceps femoris, and outer layer of semitendinosus with preservation of adductor magnus, vastus medialis, and semimembranosus. l Legs with concentric involvement of the more superficial muscles and preservation of the profound muscles with severe muscle fat replacement of tibialis anterior, extensor group, peroneal group, gastrocnemius medialis, and gastrocnemius lateralis, with preservation of tibialis posterior, and proximal soleus (not shown). Muscle MRI of subacute anti-NXP2/anti-PL7 dermatomyositis of a 25 years old patient with rapid progression of myalgia, weakness, and dyspnea with proximal lower and upper limb weakness, 16.9 times increased creatine kinase (total creatine kinase of 3,210 IU/L, reference < 190 IU/L) T1 (m, n, and o), STIR (p, q, and r). Pelvis (m), thighs (n), and legs (o) with preserved aspect on T1-weighted sequences and diffuse increased signal of muscles and subcutaneous tissue on STIR-weighted sequences of the Pelvis (p), thighs (q), and legs (r) with pronounced enhancement of tibialis posterior. Muscle MRI of chronic anti-Mi-2 beta dermatomyositis of a female patient admitted at 52 years old with a history of proximal lower limbs muscle weakness since 41 years of age, partial improvement with corticosteroid treatment, and 3.2 times increased creatine kinase (total creatine kinase of 529 IU/L, reference < 165 UI/L) T1 (s, t, and u) and STIR (v, w, and x) s Pelvis with moderate involvement of gluteus maximus, gluteus medius, and gluteus mininmus. t Thighs with severe muscle fat replacement of biceps femoris long head, and semimembranosus, and mild involvement of adductor magnus. u Legs with severe muscle fat replacement of soleus. Normal aspect of the muscles on STIR-weighted sequence (v, w, and x). Late onset TK2d: Late onset TK2 deficiency