Kleinfelder's Syndrome - Medical Overview PDF

Kleinfelder’s Syndrome · Definitions: o Klinefelter syndrome (KS), also known as polysomy X, refers to the spectrum of phenotypic and functional abnormalities that result from expression of one or more additional X chromosomes in a phenot...

Kleinfelder’s Syndrome · Definitions: o Klinefelter syndrome (KS), also known as polysomy X, refers to the spectrum of phenotypic and functional abnormalities that result from expression of one or more additional X chromosomes in a phenotypic male. o The most overt phenotypic features of KS are caused by testosterone deficiency and, directly or indirectly, by unsuppressed follicle-stimulating and luteinizing hormone secretions. · Klinefelter syndrome is associated with the potential for delay in three major areas of development: o Physical o Language o Social development. o Tall stature, small testes (i.e., male hypogonadism), development of the breasts (i.e., gynecomastia), and low sperm count (i.e., azoospermia) are common clinical signs. o The severity of clinical manifestations is directly related to the number of additional X chromosomes. o Klinefelter syndrome is named after Dr. Harry Klinefelter, who published a report in 1942 describing nine men who had enlarged breasts, sparse facial and body hair, small testes, and inability to produce sperm. o In 1959, it was learned that these men had one extra X chromosome and an XXY genotype. · Prevalence: o The classic form of KS characterized by a karyotype of 47,XXY is one of the most common genetic disorders known, occurring as frequently as 1 in every 500–1,000 male births. o The 47,XXY genotype is present in 80–90% of all cases of KS. o More than 3,000 males with this condition are born every year in the United States. o There is no racial predilection for this condition. o The prevalence rate is 5–20 times higher in individuals with mental retardation than in the general population. o Miscarriage is common and only 40% of embryos and fetuses with KS survive to full term. o The recurrence rate is not greater than that of the general population. · Significance: o The significance of KS lies primarily in the potential development of chronic illnesses and a variety of troublesome clinical manifestations. o Chronic illnesses for which KS patients are at high risk include diabetes mellitus, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA). o Klinefelter syndrome patients are also at significantly increased risk for developing a variety of cancers, including testicular and breast cancer. · Slightly more than half of all KS cases are due to maternal non-disjunction, which occurs 75% of the time during the first stage of meiosis and 25% of the time during meiosis II.  o The remaining cases are the result of paternal non-disjunction. o An increased risk for autoimmune disorders (e.g., diabetes mellitus, SLE, and RA) is presumably, in part, the result of low serum testosterone levels and high serum estradiol/ testosterone (E/T) ratios. o There is some evidence that androgens protect against autoimmunity, while estrogens promote the phenomenon. o Gynecomastia also presumably results from higher-than-normal E/T ratios. o Azoospermia and infertility are caused by atrophy and fibrosis (i.e., scarring) of the seminiferous tubules. · As described above, the most serious complications are those chronic illnesses that are often associated with KS: o diabetes mellitus (8% of all patients) o SLE o RA o testicular cancer o breast cancer o osteoporosis. o Depression may also be a significant side effect of the Condition. o Despite the numerous potential complications of KS, patients can often expect a normal lifespan · Ideally, testosterone replacement therapy is begun as the child enters puberty. o Treatment with testosterone not only helps to reverse Sexual dysfunction and muscular atrophy but also will reduce the risk for developing language problems and improve psychosocial status. o Furthermore, testosterone treatment has been shown to promote strength and physical endurance; build a more muscular physique; increase sexual desire; improve mood, self-image, and behavior; and protect against premature loss of bone mineral density. o Testosterone treatment will not, however, restore fertility. o Four methods for administration of testosterone are currently available: § parenteral, oral, transdermal, and topical. o Hypogonadism is usually treated with parenteral testosterone (i.e., enanthate or cypionate). · A typical adult dose is 200 mg intramuscularly (IM) delivered in the gluteal area every 3 weeks. o For patients 11–12 years old, 50 mg IM is delivered monthly. o Dose is adjusted according to the patient’s response. o Oral androgen preparations (methyltestosterone and fluoxymesterone) are not as effective as parenteral testosterone and occasionally cause reversible hyperbilirubinemia and jaundice. o Testosterone skin patches are available in two formulations for application to non-genital skin. o Testosterone may be mixed with an adhesive (Testoderm II), with a new patch applied daily to a different site. o This transdermal delivery system leaves a sticky residue but causes minimal skin irritation. o Androderm adheres more closely to the skin but may also cause more skin irritation.