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Spinal muscular atrophy, lower extremity-predominant, 2b, prenatal onset, autosomal dominant(SMALED2B)

MedGen UID:
1648362
Concept ID:
C4749003
Disease or Syndrome
Synonym: Spinal muscular atrophy, lower extremity-predominant, 2B, autosomal dominant
 
Gene (location): BICD2 (9q22.31)
 
Monarch Initiative: MONDO:0032660
OMIM®: 618291

Definition

SMALED2B is a severe neuromuscular disorder with onset in utero. Affected individuals show decreased fetal movements and are usually born with congenital contractures consistent with arthrogryposis multiplex congenita (AMC). After birth, they have severe hypotonia and muscle atrophy as well as respiratory insufficiency due to muscle weakness. Some patients may have dysmorphic facial features and/or abnormalities on brain imaging. Many patients die in early childhood (summary by Storbeck et al., 2017) For discussion of genetic heterogeneity of lower extremity-predominant spinal muscular atrophy, see SMALED1 (158600). [from OMIM]

Clinical features

From HPO
Clubfoot
MedGen UID:
3130
Concept ID:
C0009081
Congenital Abnormality
Clubfoot is a congenital limb deformity defined as fixation of the foot in cavus, adductus, varus, and equinus (i.e., inclined inwards, axially rotated outwards, and pointing downwards) with concomitant soft tissue abnormalities (Cardy et al., 2007). Clubfoot may occur in isolation or as part of a syndrome (e.g., diastrophic dysplasia, 222600). Clubfoot has been reported with deficiency of long bones and mirror-image polydactyly (Gurnett et al., 2008; Klopocki et al., 2012).
Femur fracture
MedGen UID:
4676
Concept ID:
C0015802
Injury or Poisoning
A break or crush injury of the thigh bone (femur).
Hand clenching
MedGen UID:
65994
Concept ID:
C0239815
Finding
An abnormal hand posture in which the hands are clenched to fists. All digits held completely flexed at the metacarpophalangeal and interphalangeal joints. In prenatal sonography of the fetal clenched hand, the index finger overlaps a clenched fist formed by the other digits. The proximal interphalangeal articulation of the index finger is flexed and ulnarly deviated, and the thumb is adducted.
Ulnar deviation of the hand
MedGen UID:
66031
Concept ID:
C0241521
Finding
Divergence of the longitudinal axis of the hand at the wrist in a posterior (ulnar) direction (i.e., towards the little finger).
Single transverse palmar crease
MedGen UID:
96108
Concept ID:
C0424731
Finding
The distal and proximal transverse palmar creases are merged into a single transverse palmar crease.
Thumbs, congenital Clasped
MedGen UID:
98140
Concept ID:
C0431886
Congenital Abnormality
In the resting position, the tip of the thumb is on, or near, the palm, close to the base of the fourth or fifth finger.
Overlapping fingers
MedGen UID:
252954
Concept ID:
C1446712
Finding
A finger resting on the dorsal surface of an adjacent digit when the hand is at rest.
Subdural hemorrhage
MedGen UID:
6775
Concept ID:
C0018946
Pathologic Function
Hemorrhage occurring between the dura mater and the arachnoid mater.
Feeding difficulties
MedGen UID:
65429
Concept ID:
C0232466
Finding
Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it.
Abnormal pinna morphology
MedGen UID:
167800
Concept ID:
C0857379
Congenital Abnormality
An abnormality of the pinna, which is also referred to as the auricle or external ear.
Spina bifida occulta
MedGen UID:
36380
Concept ID:
C0080174
Congenital Abnormality
The closed form of spina bifida with incomplete closure of a vertebral body with intact overlying skin.
Cerebellar hypoplasia
MedGen UID:
120578
Concept ID:
C0266470
Congenital Abnormality
Cerebellar hypoplasia is a descriptive term implying a cerebellum with a reduced volume, but a normal shape and is stable over time.
Hypoplasia of the corpus callosum
MedGen UID:
138005
Concept ID:
C0344482
Congenital Abnormality
Underdevelopment of the corpus callosum.
Cerebellar vermis hypoplasia
MedGen UID:
333548
Concept ID:
C1840379
Finding
Underdevelopment of the vermis of cerebellum.
Motor delay
MedGen UID:
381392
Concept ID:
C1854301
Finding
A type of Developmental delay characterized by a delay in acquiring motor skills.
Lateral ventricle dilatation
MedGen UID:
383904
Concept ID:
C1856409
Pathologic Function
Ventriculomegaly
MedGen UID:
480553
Concept ID:
C3278923
Finding
An increase in size of the ventricular system of the brain.
Perisylvian polymicrogyria
MedGen UID:
481305
Concept ID:
C3279675
Finding
Polymicrogyria (an excessive number of small gyri or convolutions) that is maximal in perisylvian regions (the regions that surround the Sylvian fissures), which may be symmetric or asymmetric and may extend beyond perisylvian regions. The Sylvian fissures often extend posteriorly and superiorly.
Extra-axial cerebrospinal fluid accumulation
MedGen UID:
868477
Concept ID:
C4022871
Finding
An increased amount of cerebrospinal fluid (CSF) in the subarachnoid space.
Cerebral cortical atrophy
MedGen UID:
1646740
Concept ID:
C4551583
Disease or Syndrome
Atrophy of the cortex of the cerebrum.
Hip dislocation
MedGen UID:
42455
Concept ID:
C0019554
Injury or Poisoning
Displacement of the femur from its normal location in the hip joint.
Congenital hip dislocation
MedGen UID:
9258
Concept ID:
C0019555
Disease or Syndrome
Kyphosis
MedGen UID:
44042
Concept ID:
C0022821
Anatomical Abnormality
Exaggerated anterior convexity of the thoracic vertebral column.
Micrognathia
MedGen UID:
44428
Concept ID:
C0025990
Congenital Abnormality
Developmental hypoplasia of the mandible.
Scoliosis
MedGen UID:
11348
Concept ID:
C0036439
Disease or Syndrome
The presence of an abnormal lateral curvature of the spine.
Multiple joint contractures
MedGen UID:
57633
Concept ID:
C0158118
Acquired Abnormality
Flexion contracture
MedGen UID:
83069
Concept ID:
C0333068
Anatomical Abnormality
A flexion contracture is a bent (flexed) joint that cannot be straightened actively or passively. It is thus a chronic loss of joint motion due to structural changes in muscle, tendons, ligaments, or skin that prevents normal movement of joints.
Muscular atrophy
MedGen UID:
892680
Concept ID:
C0541794
Pathologic Function
The presence of skeletal muscular atrophy (which is also known as amyotrophy).
Severe muscular hypotonia
MedGen UID:
326544
Concept ID:
C1839630
Finding
A severe degree of muscular hypotonia characterized by markedly reduced muscle tone.
Macrocephaly
MedGen UID:
745757
Concept ID:
C2243051
Finding
Occipitofrontal (head) circumference greater than 97th centile compared to appropriate, age matched, sex-matched normal standards. Alternatively, a apparently increased size of the cranium.
Arthrogryposis multiplex congenita
MedGen UID:
1830310
Concept ID:
C5779613
Disease or Syndrome
Multiple congenital contractures in different body areas.
Respiratory failure
MedGen UID:
257837
Concept ID:
C1145670
Disease or Syndrome
A severe form of respiratory insufficiency characterized by inadequate gas exchange such that the levels of oxygen or carbon dioxide cannot be maintained within normal limits.
Respiratory insufficiency due to muscle weakness
MedGen UID:
812797
Concept ID:
C3806467
Finding
Central apnea
MedGen UID:
854403
Concept ID:
C3887548
Disease or Syndrome
Apnea resulting from depression of the respiratory centers in the medulla oblongata. There is a lack of respiratory effort rather than obstruction of airflow.
Midface retrusion
MedGen UID:
339938
Concept ID:
C1853242
Anatomical Abnormality
Posterior positions and/or vertical shortening of the infraorbital and perialar regions, or increased concavity of the face and/or reduced nasolabial angle.
Sacral dimple
MedGen UID:
98428
Concept ID:
C0426848
Finding
A cutaneous indentation resulting from tethering of the skin to underlying structures (bone) of the intergluteal cleft.
Polyhydramnios
MedGen UID:
6936
Concept ID:
C0020224
Pathologic Function
The presence of excess amniotic fluid in the uterus during pregnancy.
Decreased fetal movement
MedGen UID:
68618
Concept ID:
C0235659
Finding
An abnormal reduction in quantity or strength of fetal movements.

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