Differentials
Other male sex chromosome aneuploidies
SIGNS / SYMPTOMS
Distinct conditions with their own phenotypes include 47,XYY; 48,XXXY; 48,XXYY; and 49,XXXXY.[14][20][33]
Many of these conditions (48,XXXY; 48,XXYY; and 49,XXXXY) have a more severe phenotype, with more significant symptoms and signs (including more marked developmental delay) than those typically seen in KS.[4] A dysmorphic bone structure, especially of the wrists and elbows (e.g., radio-ulnar synostosis), is more typical of complex aneuploidies.[20]
47,XYY individuals have normal size testes.
INVESTIGATIONS
Chromosomal karyotype analysis.
Other causes of developmental delay
SIGNS / SYMPTOMS
Variable depending on the condition. May be more global developmental delay, with receptive comprehension affected, whereas in KS expressive speech is most often affected and receptive comprehension is usually normal.[21]
INVESTIGATIONS
Chromosomal karyotype analysis (in the case of other genetic conditions).
Educational/clinical psychological assessment for specific learning difficulties (e.g., dyslexia, attention deficit hyperactivity disorder).
Central (secondary) hypogonadism
SIGNS / SYMPTOMS
Absence of developmental, social, and behavioural issues which can be seen in KS.
Central (secondary) causes of hypogonadism include parasellar tumour or apoplexy of pituitary macroadenoma.
INVESTIGATIONS
Normal or low gonadotrophin levels (LH/FSH).
Marfan syndrome
SIGNS / SYMPTOMS
Relevant family history; musculoskeletal signs (e.g., high arched palate, scoliosis, pectus excavatum, flat feet, arachnodactyly with positive thumb sign); ocular lens subluxation; aortic dilation or dissection.[34][35][36]
INVESTIGATIONS
Echocardiography may detect aortic regurgitation, dilation, or dissection.
Slit-lamp eye examination may show lens abnormalities.
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