Please use the index below to access the condition you require information on. It may take longer to find what you are looking for this way compared with our "search this site" facility in the navigator on the left but we try to point you in the most appropriate direction using this index and therefore the results should be better. For speed, this index has been split into separate alphabetical files:

Contact a Family also has information on many other specific conditions and rare disorders. If you cannot find the information you require in The Contact a Family Directory Online, you may wish to use our Contact a Family Helpline service.

XLA see Primary Immunodeficiencies
XLP see Primary Immunodeficiencies
XO syndrome see Turner syndrome
XOD see Purine & Pyrimidine Metabolic diseases
XP see Xeroderma Pigmentosum
XXX see Triple-X syndrome
XXY see Klinefelter syndrome
XXXY see Klinefelter syndrome
XXXXY see Klinefelter syndrome
XYY syndrome
X-Linked Agammaglobulinaemia see Primary Immunodeficiencies
X-Linked Hypophosphatemia
X-Linked Ichthyosis see Ichthyosis
X-Linked Lymphoproliferative syndrome see Primary Immunodeficiencies
Xanthine Oxidase/Sulphite Oxidase Deficiency see Metabolic diseases
Xanthinuria deficiency see Purine & Pyrimidine Metabolic diseases
Xeroderma Pigmentosum