MedGen

A rare progressive neurodegenerative disorder with typical onset between 50 and 65 years of age. Manifestation is of progressive impairment of higher visual processing skills and other posterior cortical functions without any evidence of ocular abnormalities. Prevalence is unknown, largely due to the lack of awareness of the syndrome and the inaccurate terminology referring to it. Alzheimer''s disease is the most common underlying pathology, but cases attributable to Dementia with Lewy Bodies, corticobasal degeneration or prion disease have also been reported. [from SNOMEDCT_US]

Pachyonychia congenita (PC) is characterized by hypertrophic nail dystrophy, painful palmoplantar keratoderma and blistering, oral leukokeratosis, pilosebaceous cysts (including steatocystoma and vellus hair cysts), palmoplantar hyperhydrosis, and follicular keratoses on the trunk and extremities. [from GeneReviews]

An aggressive and life-threatening form of thrombotic microangiopathy (TMA) characterized by profound peripheral thrombocytopenia, microangiopathic hemolytic anemia (MAHA) and organ failure of variable severity and is comprised of a congenital (cTTP) and acquired, immune-mediated (iTTP) form. [from ORDO]

Absence or abnormal closure of the choana (the posterior nasal aperture). Most embryologists believe that posterior choanal atresia results from a failure of rupture between the 35th and 38th day of fetal life of the partition which separates the bucconasal or buccopharyngeal membranes. The resultant choanal atresia may be unilateral or bilateral, bony or membranous, complete or incomplete. In over 90 per cent of cases the obstruction is bony, while in the remainder it is membranous. The bony type of atresia is commonly located 1-2 mm. anterior to the posterior edge of the hard palate, and the osseous septum varies in thickness from 1 to 10 mm. In the membranous form of choanal atresia the obstruction usually occurs further posteriorly. In approximately one third of cases the atresia is bilateral. [from HPO]