- Klinefelter's syndrome.

Klinefelter's syndrome

*Def:- It is a condition in which males have an extra X sex chromosome (i.e XXY) in his cells(1).

*Incidence:-

• The most common sex chromosome disorder (2).
• The second most common condition caused by the presence of extra chromosomes.
• Roughly it occur by 0.1% in males.
  

* Klinefelter syndrome is named after Dr. Henry Klinefelter, an endocrinologist at Massachusetts General Hospital in Boston, Massachusetts, who first described it in 1942 (3).

*Pathophysiology (1):-

• Most commonly Due to non-disjunction of chromosome X at one of the meiotic divisions so an ovum with XX chromosome when fertilized by a sperm carrying Y chromosome lead to formation of baby with XXY .
• less commonly,the condition arise when a normal ovum is fertilized by XY sperm .
• The condition may appear with XXXY or XXXXY due to non-disjunction at both meiotic divisions this will lead to more mental retardation.

*Karyotype (1) :-

• 47,XXY
• 48,XXXY
• 49,XXXXY

*Buccal smear:- +ve Barr's body.

*Hormonal assay:- decrease androgens.

*Clinical picture:-

• Infertility.
• Gynecomastia.
• Subnormal intelligence or Mental retardation.
• microorchidism (i.e. small testicles)(4).
• Absence of body hair.
• Long stature (due to absence of androgens which help closure of epiphysis).
  

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*References:-
(1) Principles of histology vol1,staff members ,faculty of medicine,mansoura university,ch3,p.g75.
(2)James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology. (10th ed.). Saunders. p 549. ISBN 0721629210.
(3)Klinefelter, HF Jr; Reifenstein, EC Jr & Albright (1942), "Syndrome characterized by gynecomastia, aspermatogenesis without a-Leydigism and increased excretion of follicle-stimulating hormone", J Clin Endocrinol Metab 2: 615–624. Klinefelter, HF (1986), "Klinefelter's syndrome: historical background and development", South Med J 79(45): 1089–1093 talks about the history of the development of the literature.
(4)Leask, Kathryn (October 2005). "Klinefelter syndrome" (HTML). National Library for Health, Specialist Libraries, Clinical Genetics. NationalLibrary for Health. . Retrieved 2007-04-07.