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J Med Genet 45:635-638 doi:10.1136/jmg.2008.057950
  • Original article

Congenital heart disease is a feature of severe infantile spinal muscular atrophy

  1. S Rudnik-Schöneborn1,
  2. R Heller2,
  3. C Berg1,
  4. C Betzler2,
  5. T Grimm3,
  6. T Eggermann1,
  7. K Eggermann1,
  8. R Wirth2,
  9. B Wirth2,4,5,
  10. K Zerres1
  1. 1
    Institute of Human Genetics, RWTH Aachen University, Aachen, Germany
  2. 2
    Institute of Human Genetics, University of Cologne, Cologne, Germany
  3. 3
    Institute of Human Genetics, University of Würzburg, Würzburg, Germany
  4. 4
    Institute of Genetics, University of Cologne, Cologne, Germany
  5. 5
    Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany
  1. Professor S Rudnik-Schöneborn, Institute of Human Genetics, Technical University of Aachen, Pauwelsstr. 30, D-52074 Aachen, Germany; srudnik-schoeneborn{at}ukaachen.de
  • Received 25 January 2008
  • Revised 1 April 2008
  • Accepted 27 April 2008
  • Published Online First 28 July 2008

Abstract

Objective: Homozygous deletions/mutations of the SMN1 gene cause infantile spinal muscular atrophy (SMA). The presence of at least one SMN2 gene copy is required for normal embryogenesis. Lack of SMN protein results in degeneration of motor neurons, while extraneuronal manifestations have been regarded as a chance association with SMA. We report on heart defects in the subgroup of congenital SMA type I patients.

Methods: Data were recruited from 65 unselected SMA I patients whose diagnosis had been confirmed genetically within the first 6 months of age. SMN2 copy numbers were analysed retrospectively and correlated with clinical findings including heart malformations.

Results: Four (6%) patients had one copy of SMN2, 56 (86%) had two and five (8%) had three SMN2 copies. Three out of four (75%) patients with a single SMN2 copy had congenital SMA with haemodynamically relevant atrial or ventricular septal defects.

Conclusions: Previous case reports of SMA I patients with congenital heart defects did not clarify whether the cardiac malformations were coincidental. Given the respective incidences of congenitally lethal SMA with a single SMN2 copy and of cardiac septal defects in humans, a chance association of both conditions would occur in less than one out of 50 million individuals. Our findings suggest that the SMN protein is relevant for normal cardiogenesis.

Footnotes

  • Funding: BW was supported by grants of the Deutsche Forschungsgemeinschaft, the Center for Molecular Medicine Cologne, the Initiative “Forschung und Therapie für SMA” and Families of SMA (USA).

  • Competing interests: None.

  • Patient consent: Parental consent obtained.