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Spinal muscular atrophy with congenital bone fractures 2(SMABF2)

MedGen UID:
907910
Concept ID:
C4225176
Disease or Syndrome
Synonym: SMABF2
 
Gene (location): ASCC1 (10q22.1)
 
Monarch Initiative: MONDO:0014807
OMIM®: 616867

Definition

Spinal muscular atrophy with congenital bone fractures is an autosomal recessive severe neuromuscular disorder characterized by onset of severe hypotonia with fetal hypokinesia in utero. This results in congenital contractures, consistent with arthrogryposis multiplex congenita, and increased incidence of prenatal fracture of the long bones. Affected infants have difficulty breathing and feeding and often die in the first days or months of life (summary by Knierim et al., 2016). For a discussion of genetic heterogeneity of spinal muscular atrophy with congenital bone fractures, see SMABF1 (616866). [from OMIM]

Clinical features

From HPO
Patent ductus arteriosus
MedGen UID:
4415
Concept ID:
C0013274
Congenital Abnormality
In utero, the ductus arteriosus (DA) serves to divert ventricular output away from the lungs and toward the placenta by connecting the main pulmonary artery to the descending aorta. A patent ductus arteriosus (PDA) in the first 3 days of life is a physiologic shunt in healthy term and preterm newborn infants, and normally is substantially closed within about 24 hours after bith and completely closed after about three weeks. Failure of physiologcal closure is referred to a persistent or patent ductus arteriosus (PDA). Depending on the degree of left-to-right shunting, PDA can have clinical consequences.
Patent foramen ovale
MedGen UID:
8891
Concept ID:
C0016522
Congenital Abnormality
Failure of the foramen ovale to seal postnatally, leaving a potential conduit between the left and right cardiac atria.
Dysphagia
MedGen UID:
41440
Concept ID:
C0011168
Disease or Syndrome
Difficulty in swallowing.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
Global developmental delay
MedGen UID:
107838
Concept ID:
C0557874
Finding
A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.
Peripheral axonal neuropathy
MedGen UID:
266071
Concept ID:
C1263857
Disease or Syndrome
An abnormality characterized by disruption of the normal functioning of peripheral axons.
Axonal loss
MedGen UID:
316962
Concept ID:
C1832338
Finding
A reduction in the number of axons in the peripheral nervous system.
Abnormal cortical gyration
MedGen UID:
343457
Concept ID:
C1856019
Anatomical Abnormality
An abnormality of the gyri (i.e., the ridges) of the cerebral cortex of the brain.
Spinal muscular atrophy
MedGen UID:
7755
Concept ID:
C0026847
Disease or Syndrome
Spinal muscular atrophy (SMA) is characterized by muscle weakness and atrophy resulting from progressive degeneration and irreversible loss of the anterior horn cells in the spinal cord (i.e., lower motor neurons) and the brain stem nuclei. The onset of weakness ranges from before birth to adulthood. The weakness is symmetric, proximal > distal, and progressive. Before the genetic basis of SMA was understood, it was classified into clinical subtypes based on maximum motor function achieved; however, it is now apparent that the phenotype of SMN1-associated SMA spans a continuum without clear delineation of subtypes. With supportive care only, poor weight gain with growth failure, restrictive lung disease, scoliosis, and joint contractures are common complications; however, newly available targeted treatment options are changing the natural history of this disease.
Muscle weakness
MedGen UID:
57735
Concept ID:
C0151786
Finding
Reduced strength of muscles.
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.
Skeletal muscle 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.
Increased variability in muscle fiber diameter
MedGen UID:
336019
Concept ID:
C1843700
Finding
An abnormally high degree of muscle fiber size variation. This phenotypic feature can be observed upon muscle biopsy.
Multiple prenatal fractures
MedGen UID:
377844
Concept ID:
C1853171
Finding
The presence of bone fractures in the prenatal period that are diagnosed at birth or before.
Generalized hypotonia
MedGen UID:
346841
Concept ID:
C1858120
Finding
Generalized muscular hypotonia (abnormally low muscle tone).
Arthrogryposis multiplex congenita
MedGen UID:
1830310
Concept ID:
C5779613
Disease or Syndrome
Multiple congenital contractures in different body areas.
Pulmonary hypoplasia
MedGen UID:
78574
Concept ID:
C0265783
Congenital Abnormality
A congenital abnormality in which the lung parenchyma is not fully developed. It may be associated with other congenital abnormalities.
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.
Neonatal respiratory distress
MedGen UID:
924182
Concept ID:
C4281993
Finding
Respiratory difficulty as newborn.
Polyhydramnios
MedGen UID:
6936
Concept ID:
C0020224
Pathologic Function
The presence of excess amniotic fluid in the uterus during pregnancy.
Premature birth
MedGen UID:
57721
Concept ID:
C0151526
Pathologic Function
The birth of a baby of less than 37 weeks of gestational age.
Decreased fetal movement
MedGen UID:
68618
Concept ID:
C0235659
Finding
An abnormal reduction in quantity or strength of fetal movements.

Professional guidelines

PubMed

Rudnik-Schöneborn S, Forkert R, Hahnen E, Wirth B, Zerres K
Neuropediatrics 1996 Feb;27(1):8-15. doi: 10.1055/s-2007-973741. PMID: 8677029

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