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Infantile spasms in a mosaic monocentric and duplicated SMC 15 patient

Kiyotaka Isobe1, Hiroshi Matsumoto1, Yoshiteru Tamura1

  • 1Department of Pediatrics, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan.

Brain & Development
|July 2, 2018
PubMed

Insights

This study reports the first case of mosaic supernumerary marker chromosome 15 (SMC(15)) with a duplicated proximal 15q in a patient with infantile spasms. The findings suggest early embryonic or maternal meiotic origin for this rare genetic condition.

Area of Science:

  • Genetics
  • Cytogenetics
  • Developmental Pediatrics

Background:

  • Infantile spasms are a severe epilepsy syndrome in infants.
  • Supernumerary marker chromosomes (SMCs) are rare genetic abnormalities.
  • Mosaicism indicates the presence of two or more cell lines with different karyotypes.

Observation:

  • A 13-month-old girl presented with infantile spasms and developmental delays.
  • G-banded chromosomal analysis revealed mosaicism for a supernumerary marker chromosome 15 (SMC(15)).
  • Further analyses included in situ hybridization, MS-MLPA, microsatellite, and SNP array.

Findings:

  • The patient's karyotype was mosaic 47,XX,+mar[26]/46,XX[4], with a de novo SMC(15) involving the 15q11-q13 region.
  • MS-MLPA confirmed methylation in the Prader-Willi/Angelman syndrome critical region.
  • Microsatellite and SNP array analyses indicated a duplicated maternal allele and an asymmetric SMC(15) structure.

Implications:

  • This is the first report of a monocentric and duplicated proximal 15q SMC(15).
  • Clinical features resemble isodicentric chromosome 15 syndrome.
  • Mosaic SMC(15) formation likely occurred during early embryogenesis or maternal meiosis.
Abstract

Keywords:
Infantile spasmsMosaicismPrader–Willi syndrome/Angelman syndrome critical region (PWACR)Supernumerary marker chromosome (SMC)idic(15)

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