MedGen

The phenotypic spectrum of SHOX deficiency disorders, caused by haploinsufficiency of the short stature homeobox-containing gene (SHOX), ranges from Leri-Weill dyschondrosteosis (LWD) at the severe end of the spectrum to nonspecific short stature at the mild end of the spectrum. In adults with SHOX deficiency, the proportion of LWD versus short stature without features of LWD is not well defined. In LWD the classic clinical triad is short stature, mesomelia, and Madelung deformity. Mesomelia, in which the middle portion of a limb is shortened in relation to the proximal portion, can be evident first in school-aged children and increases with age in frequency and severity. Madelung deformity (abnormal alignment of the radius, ulna, and carpal bones at the wrist) typically develops in mid-to-late childhood and is more common and severe in females. The phenotype of short stature caused by SHOX deficiency in the absence of mesomelia and Madelung deformity (called SHOX-deficient short stature in this GeneReview) is highly variable, even within the same family. [from GeneReviews]

Myotonia congenita is characterized by muscle stiffness present from childhood; all striated muscle groups including the extrinsic eye muscles, facial muscles, and tongue may be involved. Stiffness is relieved by repeated contractions of the muscle (the "warm-up" phenomenon). Muscles are usually hypertrophic. Whereas autosomal recessive (AR) myotonia congenita is often associated with more severe manifestations (such as progressive minor distal weakness and attacks of transient weakness brought on by movement after rest), autosomal dominant (AD) myotonia congenita is not. The age of onset varies: in AD myotonia congenita onset is usually in infancy or early childhood; in AR myotonia congenita the average age of onset is slightly older. In both AR and AD myotonia congenita onset may be as late as the third or fourth decade of life. [from GeneReviews]

Familial partial lipodystrophy is a metabolic disorder characterized by abnormal subcutaneous adipose tissue distribution beginning in late childhood or early adult life. Affected individuals gradually lose fat from the upper and lower extremities and the gluteal and truncal regions, resulting in a muscular appearance with prominent superficial veins. In some patients, adipose tissue accumulates on the face and neck, causing a double chin, fat neck, or cushingoid appearance. Metabolic abnormalities include insulin-resistant diabetes mellitus with acanthosis nigricans and hypertriglyceridemia; hirsutism and menstrual abnormalities occur infrequently. Familial partial lipodystrophy may also be referred to as lipoatrophic diabetes mellitus, but the essential feature is loss of subcutaneous fat (review by Garg, 2004). The disorder may be misdiagnosed as Cushing disease (see 219080) (Kobberling and Dunnigan, 1986; Garg, 2004). Genetic Heterogeneity of Familial Partial Lipodystrophy Familial partial lipodystrophy is a clinically and genetically heterogeneous disorder. Types 1 and 2 were originally described as clinical subtypes: type 1 (FPLD1; 608600), characterized by loss of subcutaneous fat confined to the limbs (Kobberling et al., 1975), and FPLD2, characterized by loss of subcutaneous fat from the limbs and trunk (Dunnigan et al., 1974; Kobberling and Dunnigan, 1986). No genetic basis for FPLD1 has yet been delineated. FPLD3 (604367) is caused by mutation in the PPARG gene (601487) on chromosome 3p25; FPLD4 (613877) is caused by mutation in the PLIN1 gene (170290) on chromosome 15q26; FPLD5 (615238) is caused by mutation in the CIDEC gene (612120) on chromosome 3p25; FPLD6 (615980) is caused by mutation in the LIPE gene (151750) on chromosome 19q13; FPLD7 (606721) is caused by mutation in the CAV1 gene (601047) on chromosome 7q31; FPLD8 (620679), caused by mutation in the ADRA2A gene (104210) on chromosome 10q25; and FPLD9 (620683), caused by mutation in the PLAAT3 gene (613867) on chromosome 11q12. [from OMIM]

Myhre syndrome is a connective tissue disorder with multisystem involvement, progressive and proliferative fibrosis that may occur spontaneously or following trauma or surgery, mild-to-moderate intellectual disability, and in some instances, autistic-like behaviors. Organ systems primarily involved include: cardiovascular (congenital heart defects, long- and short-segment stenosis of the aorta and peripheral arteries, pericardial effusion, constrictive pericarditis, restrictive cardiomyopathy, and hypertension); respiratory (choanal stenosis, laryngotracheal narrowing, obstructive airway disease, or restrictive pulmonary disease), gastrointestinal (pyloric stenosis, duodenal strictures, severe constipation); and skin (thickened particularly on the hands and extensor surfaces). Additional findings include distinctive craniofacial features and skeletal involvement (intrauterine growth restriction, short stature, limited joint range of motion). To date, 55 individuals with molecularly confirmed Myhre syndrome have been reported. [from GeneReviews]

Paramyotonia congenita (PMC) is an autosomal dominant myotonic disorder characterized by cold-induced prolonged localized muscle contraction and weakness. Patients may experience episodes of generalized weakness (periodic paralysis) unassociated with cold exposure (summary by Ptacek et al., 1992). [from OMIM]

Myotonia congenita is characterized by muscle stiffness present from childhood; all striated muscle groups including the extrinsic eye muscles, facial muscles, and tongue may be involved. Stiffness is relieved by repeated contractions of the muscle (the "warm-up" phenomenon). Muscles are usually hypertrophic. Whereas autosomal recessive (AR) myotonia congenita is often associated with more severe manifestations (such as progressive minor distal weakness and attacks of transient weakness brought on by movement after rest), autosomal dominant (AD) myotonia congenita is not. The age of onset varies: in AD myotonia congenita onset is usually in infancy or early childhood; in AR myotonia congenita the average age of onset is slightly older. In both AR and AD myotonia congenita onset may be as late as the third or fourth decade of life. [from GeneReviews]

Hereditary rippling muscle disease is an autosomal dominant disorder characterized by mechanically triggered contractions of skeletal muscle. In rippling muscle disease, mechanical stimulation leads to electrically silent muscle contractions that spread to neighboring fibers that cause visible ripples to move over the muscle. RMD is usually inherited as an autosomal dominant trait, but autosomal recessive inheritance has also been reported (Kubisch et al., 2005). Genetic Heterogeneity of Rippling Muscle Disease Another locus for RMD, designated RMD1 (600332), maps to chromosome 1q41. [from OMIM]

Emery-Dreifuss muscular dystrophy (EDMD) is characterized by the clinical triad of: joint contractures that begin in early childhood; slowly progressive muscle weakness and wasting initially in a humero-peroneal distribution that later extends to the scapular and pelvic girdle muscles; and cardiac involvement that may manifest as palpitations, presyncope and syncope, poor exercise tolerance, and congestive heart failure along with variable cardiac rhythm disturbances. Age of onset, severity, and progression of muscle and cardiac involvement demonstrate both inter- and intrafamilial variability. Clinical variability ranges from early onset with severe presentation in childhood to late onset with slow progression in adulthood. In general, joint contractures appear during the first two decades, followed by muscle weakness and wasting. Cardiac involvement usually occurs after the second decade and respiratory function may be impaired in some individuals. [from GeneReviews]

Centronuclear myopathy-1 (CNM1) is an autosomal dominant congenital myopathy characterized by slowly progressive muscular weakness and wasting. The disorder involves mainly limb girdle, trunk, and neck muscles but may also affect distal muscles. Weakness may be present during childhood or adolescence or may not become evident until the third decade of life, and some affected individuals become wheelchair-bound in their fifties. Ptosis and limitation of eye movements occur frequently. The most prominent histopathologic features include high frequency of centrally located nuclei in a large number of extrafusal muscle fibers (which is the basis of the name of the disorder), radial arrangement of sarcoplasmic strands around the central nuclei, and predominance and hypotrophy of type 1 fibers (summary by Bitoun et al., 2005). Genetic Heterogeneity of Centronuclear Myopathy Centronuclear myopathy is a genetically heterogeneous disorder. See also X-linked CNM (CNMX; 310400), caused by mutation in the MTM1 gene (300415) on chromosome Xq28; CNM2 (255200), caused by mutation in the BIN1 gene (601248) on chromosome 2q14; CNM4 (614807), caused by mutation in the CCDC78 gene (614666) on chromosome 16p13; CNM5 (615959), caused by mutation in the SPEG gene (615950) on chromosome 2q35; and CNM6 (617760), caused by mutation in the ZAK gene (609479) on chromosome 2q31. The mutation in the MYF6 gene that was reported to cause a form of CNM, formerly designated CNM3, has been reclassified as a variant of unknown significance; see 159991.0001. Some patients with mutation in the RYR1 gene (180901) have findings of centronuclear myopathy on skeletal muscle biopsy (see 255320). [from OMIM]

In a report on the 37th ENMC Workshop, Rudel and Lehmann-Horn (1997) stated that the sodium channelopathies can be divided into 3 different forms: paramyotonia, potassium-aggravated myotonia, and periodic paralysis. Potassium-aggravated myotonia includes mild myotonia fluctuans, severe myotonia permanens, and acetazolamide-responsive myotonia. [from OMIM]

Congenital generalized lipodystrophy type 4 (CGL4) combines the phenotype of classic Berardinelli-Seip lipodystrophy (608594) with muscular dystrophy and cardiac conduction anomalies (Hayashi et al., 2009). For a general description and a discussion of genetic heterogeneity of congenital generalized lipodystrophy, see CGL1 (608594). [from OMIM]

Congenital muscular dystrophy-dystroglycanopathy with brain and eye anomalies (type A), which includes both the more severe Walker-Warburg syndrome (WWS) and the slightly less severe muscle-eye-brain disease (MEB), is an autosomal recessive disorder with characteristic brain and eye malformations, profound mental retardation, congenital muscular dystrophy, and death usually in the first years of life. It represents the most severe end of a phenotypic spectrum of similar disorders resulting from defective glycosylation of DAG1 (128239), collectively known as 'dystroglycanopathies' (van Reeuwijk et al., 2005). For a general phenotypic description and a discussion of genetic heterogeneity of muscular dystrophy-dystroglycanopathy type A, see MDDGA1 (236670). [from OMIM]

MDDGC4 is an autosomal recessive muscular dystrophy with onset in infancy or early childhood. Cognition and brain structure are usually normal (Godfrey et al., 2006). It is part of a group of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (Mercuri et al., 2009). [from OMIM]

MDDGB2 is an autosomal recessive congenital muscular dystrophy associated with impaired intellectual development and mild structural brain abnormalities (Yanagisawa et al., 2007). It is part of a group of similar disorders, collectively known as 'dystroglycanopathies,' resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239) (Godfrey et al., 2007). For a discussion of genetic heterogeneity of congenital muscular dystrophy-dystroglycanopathy type B, see MDDGB1 (613155). [from OMIM]

MDDGB6 is an autosomal recessive congenital muscular dystrophy with impaired intellectual development and structural brain abnormalities (Longman et al., 2003). It is part of a group of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (Mercuri et al., 2009). For a discussion of genetic heterogeneity of congenital muscular dystrophy-dystroglycanopathy type B, see MDDGB1 (613155). [from OMIM]

MDDGC3 is a rare form of autosomal recessive limb-girdle muscular dystrophy with normal cognition (Clement et al., 2008). It is part of a group of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (Godfrey et al., 2007). For a discussion of genetic heterogeneity of muscular dystrophy-dystroglycanopathy type C, see MDDGC1 (609308). [from OMIM]

MDDGC2 is an autosomal recessive muscular dystrophy with onset after ambulation is achieved. Cognition is normal (Biancheri et al., 2007). It is part of a group of similar disorders resulting from defective glycosylation of alpha-dystroglycan (DAG1; 128239), collectively known as 'dystroglycanopathies' (Godfrey et al., 2007). For a discussion of genetic heterogeneity of muscular dystrophy-dystroglycanopathy type C, see MDDGC1 (609308). [from OMIM]

Brody disease (BROD) is an autosomal recessive skeletal muscle disorder characterized by exercise-induced muscle stiffness and cramps primarily affecting the arms, legs, and eyelids, although more generalized muscle involvement may also occur. Symptom onset is most often in the first decade, but many patients present and are diagnosed later in life. Skeletal muscle biopsy typically shows variation in fiber size, increased internal nuclei, and atrophy of type II muscle fibers. Rare patients have been reported to develop malignant hyperthermia after administration of anesthesia, suggesting that patients with the disorder should be tested. The disorder results from defective relaxation of fast-twitch (type II) skeletal muscle fibers due to defects in calcium homeostasis and reuptake in the muscle fiber (summary by Odermatt et al., 2000 and Molenaar et al., 2020). [from OMIM]

Familial partial lipodystrophy type 4 is an autosomal dominant metabolic disorder characterized by childhood or young adult onset of loss of subcutaneous adipose tissue primarily affecting the lower limbs, insulin-resistant diabetes mellitus, hypertriglyceridemia, and hypertension (summary by Gandotra et al., 2011). Other features may include hepatic steatosis, acanthosis nigricans, polycystic ovary syndrome, and renal disease (summary by Chen et al., 2018). For a general phenotypic description and a discussion of genetic heterogeneity of familial partial lipodystrophy (FPLD), see 151660. [from OMIM]

Isolated hemihyperplasia is an abnormality of cell proliferation leading to asymmetric overgrowth of one or more regions of the body. The term 'hemihyperplasia' has replaced the term 'hemihypertrophy' to describe accurately the increase in cell number found in these patients. The incidence of isolated hemihyperplasia is estimated to be 1 in 86,000. Idiopathic hemihypertrophy is associated with increased risk of embryonal cancers in childhood, particularly Wilms tumor (194070) (Shuman et al., 2006). Hoyme et al. (1998) provided an anatomic classification of hemihyperplasia: complex hemihyperplasia is involvement of half of the body, including at least 1 arm and 1 leg; affected parts may be contralateral or ipsilateral. Simple hemihyperplasia is involvement of a single limb. See also facial hemihyperplasia (133900). Although isolated hemihyperplasia is a distinct clinical entity, it can also occur as a feature of overgrowth syndromes, including Beckwith-Wiedemann syndrome (BWS; 130650), neurofibromatosis (NF1; 162200), Proteus syndrome (176920), and Klippel-Trenaunay-Weber syndrome (149000) (Shuman et al., 2006). [from OMIM]