Hypomagnesemia with secondary hypocalcemia in a female with balanced X;9 translocation: mapping of the Xp22 chromosome breakpoint

Hum Genet. 1994 May;93(5):587-91. doi: 10.1007/BF00202829.


Magnesium-dependent hypocalcaemia (HSH), a rare inherited disease, is caused by selective disorders of magnesium absorption. Both X-linked and autosomal recessive modes of inheritance have been reported for HSH; this suggests a genetically heterogeneous condition. A balanced de novo t(X;9)(p22;q12) translocation has been reported in a female manifesting hypomagnesemia with secondary hypocalcemia. In a lymphoblastoid cell line, derived from this patient, the normal X chromosome is preferentially inactivated, suggesting that the patient's phenotype is caused by disruption of an HSH gene in Xp22. In an attempt to define more precisely the position of the X breakpoint, we have constructed a hybrid cell line retaining the der(X)(Xqter-Xp22.2::9q12-9qter) in the absence of the der(9) and the normal X chromosome. Southern blot analysis of this hybrid and in situ hybridization on metaphase chromosomes have localized the breakpoint between DXS16 and the cluster (DXS207, DXS43), in Xp22.2. Thus, if a gene involved in HSH residues at or near the translocation breakpoint, our findings should greatly facilitate its isolation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Southern
  • Cell Transformation, Viral
  • Chromosome Aberrations
  • Chromosome Mapping
  • Chromosomes, Human, Pair 9*
  • Female
  • Humans
  • Hypocalcemia / complications
  • Hypocalcemia / genetics*
  • In Situ Hybridization
  • Magnesium Deficiency / complications
  • Magnesium Deficiency / genetics*
  • Translocation, Genetic*
  • X Chromosome*