A xanthoma (pl. xanthomas or xanthomata) (condition: xanthomatosis), from Greek  ξανθός (xanthós) yellow, is a deposition of yellowish cholesterol-rich material that can appear anywhere in the body in various disease states. They are cutaneous manifestations of lipidosis in which lipids accumulate in large foam cells within the skin. They are associated with hyperlipidemias, both primary and secondary types.Tendon xanthomas are associated with type II hyperlipidemia, chronic biliary tract obstruction, primary biliary cirrhosis, sitosterolemia and the rare metabolic disease cerebrotendineous xanthomatosis. Palmar xanthomata and tuberoeruptive xanthomata (over knees and elbows) occur in type III hyperlipidemia. Types
Xanthelasma
A xanthelasma is a sharply demarcated yellowish collection of cholesterol underneath the skin, usually on or around the eyelids. Strictly, a xanthelasma is a distinct condition, being called a xanthoma only when becoming larger and nodular, assuming tumorous proportions. Still, it is often classified simply as a subtype of xanthoma. Xanthoma tuberosum
Xanthoma tuberosum (also known as tuberous xanthoma) is characterized by xanthomas located over  tuberosity of the joints. : 530

Xanthoma tendinosum
Xanthoma tendinosum (also tendon xanthoma or tendinous xanthoma) is clinically characterized by papules and nodules found in the tendons of the hands, feet, and heel. : 531  Also associated with familial hypercholesterolemia (FH). Eruptive xanthoma
Eruptive xanthoma (ILDS E78.220) is clinically characterized by small, yellowish-orange to reddish-brown papules surrounded by an erythematous halo that appear suddenly all over the body, especially the hands, buttocks, and the extensor surfaces of the extremities. : 531  It tends to be associated with elevated triglycerides.
Hypertropia is a condition of misalignment of the eyes (strabismus), whereby the visual axis of one eye is higher than the fellow fixating eye. Hypotropia is the similar condition, focus being on the eye with the visual axis lower than the fellow fixating eye. Dissociated vertical deviation is a special type of hypertropia leading to slow upward drift of one or rarely both eyes, usually when the patient is inattentive. Presentation
Associated defects
Refractive errors such as hyperopia and anisometropia may be associated abnormalities found in patients with vertical strabismus. The vertical miscoordination between the two eyes may lead to 

Strabismic amblyopia, (due to deprivation / suppression of the deviating eye)
cosmetic defect (most noticed by parents of a young child and in photographs)
Face turn, depending on presence of binocular vision in a particular gaze
diplopia or double vision - more seen in adults (maturity / plasticity of neural pathways) and suppression mechanisms of the brain in sorting out the images from the two eyes. cyclotropia, a cyclotorsional deviation of the eyes (rotation around the visual axis), particularly when the root cause is an oblique muscle paresis causing the hypertropia. Causes
Hypertropia may be either congenital or acquired, and misalignment is due to imbalance in extraocular muscle function. The superior rectus, inferior rectus, superior oblique, and inferior oblique muscles affect the vertical movement of the eyes. These muscles may be either paretic, restrictive (fibrosis) or overactive effect of the muscles.