# Pseudoathletic appearance

Pseudoathletic appearance is a medical sign meaning to have the false appearance of a well-trained athlete due to pathologic causes (disease or injury) instead of true athleticism. It is also referred to as a Herculean or bodybuilder-like appearance. It may be the result of muscle inflammation (immunity-related swelling), muscle hyperplasia, muscle hypertrophy, muscle pseudohypertrophy (muscle atrophy with infiltration of fat or other tissue), or symmetrical subcutaneous (under the skin) deposits of fat or other tissue.
The mechanism resulting in this sign may stay consistent or may change, while the sign itself remains. For instance, some individuals with Duchenne and Becker muscular dystrophy may start with true muscle hypertrophy, but later develop into pseudohypertrophy.
In healthy individuals, resistance training and heavy manual labour creates muscle hypertrophy through signalling from mechanical stimulation (mechanotransduction) and from sensing available energy reserves (such as AMP through AMP-activated protein kinase); however, in the absence of a sports or vocational explanation for muscle hypertrophy, especially with accompanying muscle symptoms (such as myalgia, cramping, or exercise intolerance), then a neuromuscular disorder should be suspected.
As muscle hypertrophy is a response to strenuous anaerobic activity, ordinary everyday activity would become strenuous in diseases that result in premature muscle fatigue (neural or metabolic), or disrupt the excitation-contraction coupling in muscle, or cause repetitive or sustained involuntary muscle contractions (fasciculations, myotonia, or spasticity). In lipodystrophy, an abnormal deficit of subcutaneous fat accentuates the appearance of the muscles, though in some forms the muscles are quantifiably hypertrophic (possibly due to a metabolic abnormality).

## Diseases
### Skeletal muscle

| Disease grouping | Disease | Muscle(s) typically affected | Age of onset | Biopsy, ultrasonography, CT scan or MRI |
| Hyperplasia | Myostatin-related muscle hypertrophy (MSTN gene) | General | Prenatal-onset | Myofibre hyperplasia and decreased adipose tissue. |
| Hyperplasia | Beckwith–Wiedemann syndrome | Macroglossia /hemihypertrophy of limb or body | Prenatal to infantile-onset | Wide phenotypic variability. Macroglossia (enlarged tongue) and hemihyperplasia (enlargement on one side of the body) in general or an isolated limb. |
| Hyperplasia | Aberrant muscle syndrome (congenital muscular hyperplasia of the hand and/or foot) (PIK3CA-related overgrowth spectrum) | Hand and/or foot | Childhood-onset | Muscle hyperplasia and ectopic (out of place) striated muscle fibres in dermis and hypodermis. |
| Parasitic | Disseminated muscular cysticercosis syndrome | General /calf muscle | Variable | Pork tapeworm cysts |
| Parasitic | Trichinosis | General | Variable | Skeletal muscle inflammation (myositis) secondary to roundworm cysts and larvae. |
| Inflammation | Inflammatory myopathies (Focal myositis, polymyositis, granulomatous myositis, inclusion body myositis) | Calf muscle/general | | |
| Inflammation | Sarcoid granulomas/Sarcoidosis | Calf muscle/general | | Inflammatory cells and deposits of sarcoid granulomas |
| Inflammation | Amyloid deposits/Amyloidosis (Inflammatory protein serum amyloid A, or in association with inflammatory diseases) | Calf muscle/general | | Amyloid deposits |
| Ossification | Fibrodysplasia ossificans progressiva (formerly known as myositis ossificans progressiva) | General | | Episodic inflammatory flare-ups involving skeletal muscle (myositis) secondary to muscle tissue turning into bone (ossification) |
| Ossification | Non-hereditary myositis ossificans | General | | Episodic inflammatory flare-ups involving skeletal muscle (myositis) secondary to muscle tissue turning into bone (ossification) |
| Muscular dystrophy | Duchenne muscular dystrophy | Calf muscle /general | Childhood-onset | Muscle hypertrophy may precede pseudohypertrophy by infiltration of fatty tissue |
| Muscular dystrophy | Becker muscular dystrophy | Calf muscle /general | Variable | Muscle hypertrophy may precede pseudohypertrophy by infiltration of fatty tissue |
| Muscular dystrophy | Facioscapulohumeral muscular dystrophy | Calf muscle/infraspinatus /deltoid muscles | | "Poly-hill sign" (hypertrophy and atrophy of shoulder girdle muscles) and "Popeye sign" (atrophy of biceps, but spared forearm). |
| Muscular dystrophy | Myotonic dystrophy types 1 & 2 | Calf muscle | Variable | Variable. Calf muscle hypertrophy rare in type 1, EMG showing persistent myotonic discharges in affected muscles. Calf muscle hypertrophy common in type 2 (about 50%), EMG may be normal or show myotonic discharges. |
| Muscular dystrophy | Limb-girdle muscular dystrophy (LGMD) types R1 (formerly, 2A), R3 (2D), R4 (2E), R5 (2C), R6 (2F), R7 (2G), R8 (2H), R9 (2I), R10 (2J), R11 (2K), R12 (2L), R13 (2M), R14 (2N), R15 (2O), R16 (2P), R19 (2T), R20 (2U), R23, R24, R26, R28 | Calf muscle /macroglossia /general | Variable | Hypertrophy and/or pseudohypertrophy by fatty infiltration of muscle. Classic dystrophic changes include myonecrosis and regeneration, variations in muscle fibre size, myofibrosis, fatty infiltration. LGMD1H shows histochemical evidence suggestive of a mitochondrial myopathy and since 2017 was excluded from LGMD (see below under metabolic myopathy). |
| Muscular dystrophy | Muscular dystrophy-dystroglycanopathy (MDDG) (types A2, A4, B1, B2, B5, B6, C2, C3, C4, C5, C7, C8, C9, C12, C14) | Calf muscle | | Hypertrophy and/or pseudohypertrophy by fatty infiltration of muscle. |
| Muscular dystrophy | Myopathy, X-linked, with postural muscle atrophy (formerly Emery–Dreifuss muscular dystrophy 6, X-linked) | Proximal muscles | Variable (late childhood to adult-onset) | Muscle hypertrophy precedes muscle atrophy. Biopsy shows myopathic or dystrophic changes, rimmed vacuoles, cytoplasmic bodies, and granulofilamentous material. |
| Muscular dystrophy | Emery–Dreifuss muscular dystrophy 2, autosomal dominant (EDMD2) (formerly, LGMD1B) | Calf muscle | Childhood-onset | Calf muscle hypertrophy. Biopsy shows neurogenic and myopathic changes, including fibre type variation, central nuclei, fibrosis and fatty infiltration. EMG myopathic. |
| Muscular dystrophy | Miyoshi muscular dystrophy 3 | Calf muscles /extensor digitorum brevis muscles | Adult-onset | Muscle hypertrophy and/or pseudohypertrophy by infiltration of fatty tissue. Muscle hypertrophy precedes muscle atrophy. |
| Muscular dystrophy | Myopathy, vacuolar, with CASQ1 aggregates | Calf muscle | Adolescence to adult-onset | Calf muscle hypertrophy in some. Muscle biopsy shows vacuoles predominantly in type II (fast-twitch/glycolytic) fibres, rare necrotic fibres, CASQ1-immunopositive inclusions, decreased density of calcium release units, abnormal sarcoplasmic reticulum elements, enlarged terminal cisternae of the sarcoplasmic reticulum, and enlarged vesicles of sarcoplasmic reticulum origin. |
| Muscular dystrophy | Myofibrillar myopathy 3 (MFM3) (MYOT gene, Ser55Phe missense mutation phenotype) (formerly, LGMD1A) | Neck, trunk, thigh and leg muscles | Adult-onset | Pseudohypertrophy by infiltration of fatty tissue. Muscle biopsy showed myofibrillar myopathy with prominent protein aggregates, type I (slow-twitch/oxidative) fibre predominance, other abnormalities. EMG myopathic with spontaneous activity at rest, with or without complex repetitive discharges. Muscles felt stiff upon palpitation |
| Muscular dystrophy | Myofibrillar myopathy 8 (MFM8) (PYROXD1 gene) | Rectus femoris/calf muscle | Variable | Hypertrophy and/or pseudohypertrophy by infiltration of fatty tissue. Fatty atrophy of muscle common, except the rectus femoris (a thigh muscle) commonly spared or hypertrophic. Pseudohypertrophy of calf muscles. EMG myopathic. Muscle biopsy commonly showed dystrophic changes, myofibrillar inclusions, nemaline rods, internalized nuclei, other myopathic features. |
| Muscular dystrophy | Myofibrillar myopathy 9 with early respiratory failure (MFM9) | Calf muscle | Variable adult-onset (20s-70s) | Calf muscle hypertrophy. EMG myopathic. Muscle biopsy myopathic or dystrophic changes with fibre splitting, eosinophilic cytoplasmic inclusions consistent with myofibrillar myopathy, rimmed vacuoles, and increased connective or fatty tissue. |
| Muscular dystrophy | Myofibrillar myopathy 10 (MFM10) | Trapezius and latissimus dorsi muscles | Childhood to young adult-onset | Hypertrophic neck and shoulder girdle muscles. Muscle biopsy shows structural abnormalities, lobulated type I (slow-twitch/oxidative) muscle fibres, irregular intermyofibrillar network, autophagic vacuoles with lipoprotein deposits, and sarcolemmal abnormalities. |
| Muscular dystrophy | Myofibrillar myopathy 11 (MFM11) | Calf muscle | Childhood-onset | Pseudohypertrophic calf muscles (mild fatty infiltration seen on MRI). Biopsy shows type I (slow-twitch/oxidative) fibre predominance, centralized nuclei, core-like lesions, abnormal myofibrillar aggregates or inclusions. EMG myopathic. |
| Muscular dystrophy | Myopathy, distal, Tateyama type (MPDT) | Calf muscle | Childhood to young adult onset | Hypertrophic calf muscles. Atrophy in muscles of hands and feet. Biopsy shows internal nuclei, absence of CAV3 staining, mild variation in fibre size, type I (slow-twitch/oxidative) fibre type predominance. EMG myopathic, low amplitude and short duration MUAPs. |
| Muscular dystrophy | Myopathy, distal, infantile-onset | Calf muscle | Infantile-onset | Hypertrophic calf muscles. Biopsy shows fibre size variation, increased internal nuclei, degenerating fibres, increased connective tissue and fat. EMG myopathic in affected muscles, normal in peroneal (outer calf) muscles. |
| Muscular dystrophy | Muscular dystrophy, autosomal recessive, with cardiomyopathy and triangular tongue (MDRCMTT) (formerly, LGMD2W) | Calf muscle and macroglossia | Childhood-onset | Hypertrophic calf muscles and enlarged tongue with a small tip (triangle tongue). Biopsy shows dystrophic features with fibre size variation, necrotic fibres, scattered fibrosis and fatty infiltration. |
| Non-dystrophic myotonias and pseudomyotonias (delayed muscle relaxation) | Myotonia congenita (Chloride channelopathy, CLCN1 gene) | Calf muscle /general | | Calf muscle hypertrophy. |
| Non-dystrophic myotonias and pseudomyotonias (delayed muscle relaxation) | Potassium-aggravated myotonia, paramyotonia congenita (Sodium channelopathy, SCN4A gene) | Calf muscle /general | | Muscle hypertrophy. |
| Non-dystrophic myotonias and pseudomyotonias (delayed muscle relaxation) | Brody disease (formerly, Brody myopathy) | Calf muscle | | Variable Commonly marked variability of muscle fibre size, type II (fast-twitch/glycolytic) muscle fibres may be abnormally increased or decreased, usually increased internal nuclei, rarely nuclear centralization or nuclear clumping. Muscle activity is electrically silent on EMG. |
| Non-dystrophic myotonias and pseudomyotonias (delayed muscle relaxation) | Rippling muscle disease (RMD) types 1 & 2 (RMD2 formerly, LGMD1C) | Calf muscle /general | | Muscle hypertrophy. Muscle activity is electrically silent on EMG. |
| Lipodystrophy | Familial partial lipodystrophy (Köbberling–Dunnigan syndrome) | Calf muscle /general | Adolescence-onset | Hypertrophy of calf muscles |
| Lipodystrophy | Congenital generalized lipodystrophy (Berardinelli–Seip syndrome) | General | Infantile-onset | Muscle hypertrophy |
| Hypertonia (spasticity or rigidity) | Spastic cerebral palsy | Calf muscle | Childhood-onset | accumulation of hydroxyproline (aminoacid exclusive to collagen) in calf muscles |
| Hypertonia (spasticity or rigidity) | Stiff-person syndrome | Torso/limbs | Adult-onset | Muscle hypertrophy and EMG demonstrates co-contraction of agonist and antagonist muscles and/or continuous motor unit activity in affected muscles. |
| Denervation (pseudo)hypertrophy | Peripheral nerve traumatic injury | Calf muscle | Variable | |
| Denervation (pseudo)hypertrophy | Disorders of the anterior horn cells (such as poliomyelitis, spinal muscular atrophy, and Charcot–Marie–Tooth disease) | Calf muscle | Variable | |
| Denervation (pseudo)hypertrophy | Radiculopathy (pinched nerve) | Calf muscle/thigh muscle | Adult-onset | Variable. Hypertrophy or pseudohypertrophy by fatty infiltration of muscle. |
| Endocrine myopathies | Kocher–Debre–Semelaigne syndrome | Calf muscle/general | Childhood-onset | Muscle hypertrophy, abnormal glycogen accumulation (impaired glycogenolysis), mucopolysaccharide deposits, atrophy of type II (fast-twitch/glycolytic) muscle fibres. EMG normal or myopathic low amplitude and short MUAPs (motor unit action potentials), decrease in muscle carnitine. |
| Endocrine myopathies | Hoffmann syndrome | Calf muscle/general | Adult-onset | Variable (with or without mucoid deposits). Muscle hypertrophy, abnormal glycogen accumulation (impaired glycogenolysis), mucopolysaccharide deposits, atrophy of type II (fast-twitch/glycolytic) muscle fibres, damaged mitochondria. EMG may be normal, neuropathic, myopathic, or mixed type. Decrease in muscle carnitine. |
| Endocrine myopathies | Denervation pseudohypertrophy of calf muscles secondary to diabetic neuropathy | Calf muscle | Adult-onset | Fatty infiltration of calf muscles (pseudohypertrophy) and myofibrosis. |
| Endocrine myopathies | Acromegaly/Gigantism | General | | Muscle hypertrophy |
| Metabolic myopathies | Late-onset Pompe disease (Glycogen storage disease type II) (formerly, LGMD2V) | Calf muscle/macroglossia | Variable (childhood to adulthood, but not infantile-onset) | Calf muscle hypertrophy, abnormal glycogen accumulation within the lysosomes of muscle cells due to impaired glycogenolysis. Macroglossia (enlarged tongue) due to infiltration of fat, or very rarely a benign tumour (pseudohypertrophy). The fatty tissue is seen on MRI as "bright tongue sign." |
| Metabolic myopathies | Cori/Forbes disease (Glycogen storage disease type III) | Sternocleidomastoid, trapezius and quadriceps muscles/thigh muscles | Variable | Hypertrophy and pseudohypertrophy. Abnormal glycogen accumulation within the cytosol of muscle cells due to impaired glycogenolysis. |
| Metabolic myopathies | McArdle disease (Glycogen storage disease type V) | Calf muscle /quadriceps /deltoid and bicep muscles | Childhood-onset | Muscle hypertrophy, lean calf muscles, abnormal glycogen accumulation within the cytosol of muscle cells due to impaired glycogenolysis. EMG normal or myopathic low amplitude, short duration polyphasic MUAPs (motor unit action potentials). EMG results may be dynamic: more likely to be myopathic after 5 minutes of high-intensity isometric exercise. |
| Metabolic myopathies | Muscle glycogen storage disease of unknown etiology in conjunction with dystrophin gene deletion | Calf muscle | Adult-onset (30s) | Calf muscle hypertrophy. Muscle biopsy showed abnormal glycogen accumulation, without dystrophic changes. Histochemical studies were negative for any known disorder of glycogen metabolism. Atrophy of quadriceps (thigh) muscles and hip abductors. EMG showed myopathic changes in the legs, most prominent in the thighs and minimal changes in the arms. Predominance of type IIA (fast-twitch/oxidative) muscle fibres, deficiency of type I (slow-twitch/oxidative) and type IIB muscle fibres (fast-twitch/glycolytic). Histochemistry showed normal phosphorylase and other enzymes. Biochemical studies showed a phosphorylase activity just below normal range, with other activities being normal. Southern blot analysis revealed a deletion of exons 45 to 48 of dystrophin gene, which on Western blotting was shown to produce normal amounts of truncated dystrophin. |
| Metabolic myopathies | Hereditary myopathy with lactic acidosis (HML) (gene ISCU) | Calf muscle | Childhood-onset | Some have hypertrophy of calf muscles. Upon palpitation, some feel abnormally hard with or without tenderness. Radiological examination showed no infiltration of fatty tissue. Muscle biopsy showed proliferation of type I (slow-twitch/oxidative) muscle fibres, abnormal mitochondrial iron and lipid deposits. Histochemical studies show deficiency of succinate dehydrogenase and aconitase, defective oxidative phosphorylation. Some showed evidence of necrosis and regeneration. EMG is normal or myopathic increased polyphasic MUAPs. EMG results may be dynamic: more likely to have increased polyphasic MUAPs after exercise. |
| Metabolic myopathies | Muscular dystrophy, limb-girdle, type 1H (As of 2017 was excluded from LGMD, but not yet assigned new nomenclature) | Calf muscle | Variable (teens-50s) | Muscle hypertrophy, muscle fibre type variation, ragged red fibres, absence of cytochrome c oxidase staining, evidence of mtDNA deletions, defective oxidative phosphorylation suggestive of mitochondrial myopathy. |
| Malnutrition (poor diet, malabsorption diseases, or drug side effect such as lipase inhibitor Orlistat) | Vitamin D deficiency myopathy (also known as osteomalacic myopathy) | Calf muscle | Adult-onset (no rickets) | Muscle hypertrophy in rare cases. Commonly abnormal glycogen accumulation (impaired glycogenolysis), atrophy of type II (fast-twitch/glycolytic) muscle fibres, enlarged inter-fibrillar spaces; rarely infiltration of fat (pseudohypertrophy), and fibrosis. EMG myopathic low amplitude, short duration polyphasic MUAPs (motor unit action potentials). |
| Malnutrition (poor diet, malabsorption diseases, or drug side effect such as lipase inhibitor Orlistat) | Vitamin D deficiency myopathy secondary to Celiac disease | Calf muscle | Adult-onset (no rickets) | |
| Congenital myopathies | Central core disease Congenital myopathy 1 A & B, Malignant hyperthermia susceptibility (RYR1 gene) | Calf muscle | | Muscle hypertrophy |
| Congenital myopathies | Centronuclear myopathy Types 1, 2, & 6 | Calf muscle /paraspinal muscles/ general | Variable. Childhood- to adult-onset | Muscle hypertrophy. Muscle biopsy shows numerous centrally located nuclei, and may have other variable myopathic features. |
| Congenital myopathies | Congenital myopathy 5 with cardiomyopathy (CMYP5) | Calf muscle | Infantile-onset | Hypertrophic calf muscles. Biopsy shows centralized nuclei, type I (slow-twitch/oxidative) fibre predominance, mini core-like lesions with mitochondrial depletion and sarcomeric disorganization. Dystrophic changes more apparent in second decade. |
| Congenital myopathies | Congenital myopathy 9B, proximal, with minicore lesions | Calf muscle | Infantile-onset | Pseudohypertrophy due to fatty infiltration. Biopsy shows type I (slow-twitch/oxidative) fibre predominance, increased internal nuclei, Z-band streaming, and minicores that disrupt the myofibrillar striation pattern. |
| Congenital myopathies | Congenital myopathy 24 (CMYP24) (formerly, nemaline myopathy 11, autosomal recessive) | Calf muscle | Childhood-onset | Calf muscle pseudohypertrophy. Biopsy shows fibre size variation, type I (slow-twitch/oxidative) fibre predominance, cytoplasmic and intranuclear nemaline bodies. MRI shows fatty infiltration of tongue, back, thigh and calf muscles. EMG shows chronic denervation and myopathy. |
| Congenital myopathies | Tubular aggregate myopathy types 1 & 2 (genes STIM1, ORAI1) | Calf muscle | Typically childhood-onset | Hypertrophy of type I and type II muscle fibres, type I (slow-twitch/oxidative) fibre predominance, fatty infiltration of affected muscles, tubular aggregates (TAs) mainly in type I fibres arranged in honeycomb-like structures (transversal sections) or aligned in parallel (longitudinal sections), internal nuclei, particulate glycogen scattered between tightly packed tubules, occasional lipofuscin granules within large TAs, EMG normal to myopathic. Muscle oedema and fibrosis may accompany fatty infiltration. |
| Myosin myopathies and Laing distal myopathy (gene MYH7) | Laing distal myopathy (Myopathy, distal, 1; MPD1) | Calf muscle | Variable. Typically childhood-onset | Wide phenotypic variability. Typically hypertrophic calf muscles, atrophy of anterior compartment tibial muscles, predominance of type I fibres and numerous small type I fibres. Common are internal nuclei, structural abnormalities (especially minicores), and mitochondrial abnormalities (ragged red fibres). Rarely muscle necrosis, protein aggregates, rimmed vacuoles, filamentous inclusions, muscle atrophy with fat or connective tissue replacement (pseudohypertrophy), cytoplasmic bodies, and myofibrillar alterations. EMG myopathic or neurogenic. |
| Myosin myopathies and Laing distal myopathy (gene MYH7) | Myosin storage myopathy (Congenital myopathy 7A, myosin storage; CMYP7A) | Calf muscle | Variable. Typically childhood-onset | Wide phenotypic variability. Typically fatty infiltration of calf muscles (pseudohypertrophy), type I (slow-twitch/oxidative) fibre predominance, type I fibres have abnormalities (hyaline bodies and myosin protein aggregates), and generalized muscle atrophy. Other variable muscle biopsy findings may be seen in addition. EMG is myopathic. |
| Tumours | Infiltrating lipoma | Calf muscle | | Pseudohypertrophy |
| Tumours | Sarcoma | | | Pseudohypertrophy |
| Vascular | Intramuscular hematoma due to inherited or acquired coagulopathy | | | Muscle swollen due to intramuscular bleeding and impaired blood clotting. |
| Vascular | Diabetic muscle infarction | Quadriceps | Adult-onset | Commonly in the thigh (quadriceps). Short-term, painful swelling of the muscle that is firm and warm to the touch. Muscle biopsy shows necrosis and oedema. |
| Vascular | Compartment syndrome (Acute or chronic exertional) | Calf muscles /general | Adult-onset | Muscle swelling due to increased internal pressure from bleeding and inflammatory reactions. Muscle swelling in chronic exertional compartment syndrome relieves with rest. Acute compartment syndrome due to injury requires surgery. |
| Short stature | Myhre syndrome (chronic denervation hypertrophy secondary to primary disease) | General | Childhood-onset | Muscle hypertrophy |
| Short stature | Schwartz-Jampel syndrome | | Infantile-onset | Muscle hypertrophy |
| Short stature | Uruguay faciocardiomusculoskeletal syndrome | | Early childhood-onset | Muscle hypertrophy |
| Short stature | Nivelon-Nivelon-Mabille syndrome | | Prenatal-onset | Muscle hypertrophy in some |
| Short stature | Satoyoshi syndrome | General | Childhood to early adolescence-onset | Muscle hypertrophy |
| Short stature | Stormorken syndrome (gene STIM1) | Calf muscle | Childhood-onset | Fatty infiltration of affected muscles, tubular aggregates (TAs) mainly in type I (slow-twitch/oxidative) fibres arranged in honeycomb-like structures (transversal sections) or aligned in parallel (longitudinal sections), type I (slow-twitch/oxidative) muscle fibre predominance, internal nuclei, |
| Exclusively facial muscles | Hemifacial myohyperplasia (HMH) | Unilateral facial expression muscles and/or masticatory muscles | Prenatal-onset | Unilateral (one side of the face) hyperplasia in the muscles controlling facial expression and/or mastication (chewing) |
| Exclusively facial muscles | Idiopathic unilateral masseter muscle hypertrophy | Masticatory muscles | Adolescence-onset | Unilateral (one side of the face) hypertrophy of masticatory muscles (used for chewing food). Biopsy showed hypertrophic muscle fibres. |
| Exclusively facial muscles | Masseter muscle hypertrophy | Masticatory muscles | Adolescence-onset | Bilateral (both sides of the face) muscle hypertrophy of the masticatory muscles (used for chewing food) |
| Exclusively facial muscles | Bruxism (excessive teeth grinding or clenching) | Masticatory muscles | | Hypertrophy of masticatory muscles (used for chewing food) |
| Other | Syringomyelia (cyst or cavity within spinal cord) | Upper limbs /calf muscle | | Muscle hypertrophy |
| Other | Peripheral nerve hyperexcitability syndromes (Neuromyotonia, Morvan syndrome, Benign fasciculation syndrome, Cramp fasciculation syndrome) | Upper limbs /calf muscle | | Muscle hypertrophy |
| Other | Episodic ataxia, type 1 (EA1) (Episodic ataxia with myokymia; EAM) (Potassium channelopathy, gene KCNA1) | Calf muscle | Childhood-onset | Calf muscle hypertrophy. EMG shows polyphasic continuous motor unit discharges. Muscle biopsy shows enlargement of type I muscle fibres, consistent with denervation. |
| Other | Myasthenic syndrome, congenital, 23, presynaptic (CMS23) | Calf muscle | Infantile-onset | Calf muscle hypertrophy. EMG shows abnormal jitter. Biopsy normal or non-specific myopathic features. |
| Other | Familial myoedema, muscular hypertrophy and stiffness | Calf muscle | Childhood-onset | Calf muscle hypertrophy Muscle biopsy showed unspecified myopathic changes, many vacuoles between myofibrils. EMG showed no myopathic discharges. Myoedema response in whole body. |
| Other | Strongman syndrome (Muscle hypertrophy syndrome, myalgic) | General | Childhood-onset | Muscle hypertrophy |
| Other | Hypertrophia musculorum vera (Latin for true muscle hypertrophy) | Calf muscle /masseter muscle | Variable. Typically adult-onset (early 20s) | Calf muscle hypertrophy, there may also be hypertrophy of masseter muscles (used for chewing food). Biopsy of affected muscles shows hypertrophy of muscle fibres with occasional central migration of sarcolemmal nuclei. EMG of affected muscles is myopathic. |
| Other | TANGO2-related disease (Metabolic crises, recurrent, with rhabdomyolysis, cardiac arrhythmias, and neurodegeneration; MECRCN) | Hemihypertrophy of arm and leg | Infantile-onset | Wide phenotypic variability. Hemihypertrophy of right arm and leg (rare). Abnormal autophagy and mitophagy, may have normal or abnormal secondary fatty acid metabolism and/or respiratory chain dysfunction in muscle biopsy. |
| Other | Atypical Werner syndrome | Limbs | Variable. Adolescence- or early adult-onset | Muscle hypertrophy of the limbs |
| Other | Dilated cardiomyopathy 1X (CMD1X) | Calf muscle | | Bilateral calf muscle hypertrophy |
| Other | Chromosome Xp21 deletion syndrome | Calf muscle | Childhood-onset | Bilateral calf muscle hypertrophy |
| Other | Neuromuscular oculoauditory syndrome (NMOAS) | Calf muscle | | |
| Other | Myopathy with extrapyramidal signs (MPXPS) | Calf muscle | | |
| Other | Habitual toe walking secondary to autism spectrum disorder | Calf muscle | Childhood-onset | Muscle hypertrophy |

### Skin and other non-muscle tissue

| Disease grouping | Disease | Body part(s) typically affected | Age of onset | Biopsy, ultrasonography, CT scan or MRI |
| Lipomatosis | Madelung disease | Upper trunk | Adult-onset | Symmetrical subcutaneous adipose tissue (unencapsulated lipomas) |
| Parasitic | Disseminated cysticercosis | Skin/General | Variable | Pork tapeworm cysts |
| Inflammation of the joint | Amyloidosis | shoulders "shoulder pad sign" | Adult-onset | Amyloid deposits, significant thickening of the subdeltoid bursa |
| Synovial fluid leak | Burst Baker's cyst | Calf | Adult-onset | Swelling of the calf due to synovial fluid leaking into it from a burst Baker's cyst. |
| Phlebetic lymphedema | Venous thrombosis/ Post-thrombotic syndrome | Lower extremities | Adult-onset | Swelling of the legs with discolouration of the skin (darkening or reddening) due to a blood clot in a deep vein and subsequent swelling of lymphatic system. |
| Phlebetic lymphedema | Chronic venous insufficiency | Lower extremities | Adult-onset | Swelling of the legs, with possible discolouration of the skin (darkening or reddening). Swelling and discolouration is most prominent towards the direction of gravity (foot/ankle when standing). Depending on severity, the calf and thigh may appear swollen. Skin conditions can develop such as venous ulcers, lipodermatosclerosis, and stasis dermatitis. |