American Journal of Medical Genetics 36:365 (1990)
Letter to the Editor
Isochromosome Xq in Klinefelter Syndrome
To the Editor:
In the last issue of this Journal we read with interest the paper by Richer et al. [19891. In this paper the authors stated that: Data on Klinefelter syndrome (KS) and an isochromosome Xq have been mentioned only briefly in the literature [Chapdelaine et al., 19791, and since a few other cases have now been reported, to the best of our knowledge bringing the total number on eight.
Recently, we reported [Kleczkowska et al., 19881 the Leuven experience 1966-1987 on X-chromosome polys- omy in the male. Of a total of 569 males with KS and X-chromosome polysomy diagnosed in this period we found an isochromosome Xq in two patients. A 28-year- old man with normal secondary sexual characteristics, delayed puberty (after the age of 17 years), slight gyne- comastia, small atrophic testes and complete azoosper- mia presented a 47,Xi(Xq)Y karyotype. Height was 198 cm and weight 89 kg at the time of examination, and hormonal investigations showed LH, FSH and tes- tosterone values of 14.2 rn/U/ml, 31.4 m/U/ml and 129 ng/lOO ml, respectively. A 47,XXY/48,XXi(Xq)Y mosai- cism was detected in lymphocyte and fibroblast cultures of an 18-year-old man with hypogonadism, small, soft testes, and azoospermia. Height, span, and weight were 164.5 cm, 171 cm, and 57 kg, respectively. Testicular biopsy showed fibrotic seminiferous tubules, absence of spermatogonia and hypertrophy of Leydig cells.
The present data suggest that iso(Xq) chromosome formation may be detected in 1 of 250 males with X-chro-
Received for publication March 31, 1989. Address reprint requests to Dr. J.P. Fryns, Center for Human
Genetics, U.Z. Gasthuisberg, Herestraat 49, B-3000, Leuven, Bel- gium.
0 1990 Wiley-Liss, Inc.
mosome polysomy and KS. This confirms the low inci- dence of this type of X-chromosome abnormality in KS as given by Richer et al.  in their report. However, the clinical and hormonal data of the Leuven patients do not support the delineation of a specific isochromosome Xq Klinefelter syndrome as suggested by these au- thors. More specifically, we could not confirm normal testosterone values, nor the normal height found by these authors.
REFERENCES Chapdelaine A, Richer CL, Cadotte R, Murer-Orlando M, Roberts KD,
Bleau G (1979): Isochromosome Xq in a patient with Klinefelters syndrome and normal masculinization. Fertil Steril 32249 (ab- stract).
Kleczkowska A, Fryns JP, Van den Berghe H (19881: X-chromosome polysomy in the male. Hum Genet 80:16-22.
Richer CL, Bleau G, Chapdelaine A, Murer-Orlando M, Lemieux N, Cadotte M (1989): A man with isochromosome Xq Klinefelter syn- drome with lack of height increase and normal androgenization. Am J Med Genet 3242-44.
Jean-Pierre Fryns Alice Kleczkowska Centre for Human Genetics Department of Human Biology Omer Steeno Division of Andrology Department of Internal Medicine University of Leuven, Belgium