DYSPLASIA

malformation of some bodily structure or tissue; the term most commonly denotes a malformation of bone that may occur in any part of the body. Several dysplasias are well-defined diseases in humans. Chondroectodermal dysplasia (Ellis-van Creveld syndrome) is a very rare, congenital disorder. It is heritable (autosomal recessive). Affected individuals exhibit heart abnormalities (which may cause early death), extra digits, defective dentition, poorly formed nails, dwarfing, and often knock-knees and fusion of hand bones. The disorder reaches its highest known frequency among the Old Order Amish in Pennsylvania, in which 5 in every 1,000 births are affected. Progressive diaphyseal dysplasia (Engelmann's syndrome) is an uncommon heritable (autosomal recessive) disorder beginning in childhood. The shafts of the bones and the skull vault become thickened; there is no pain, but individuals grow to be taller than normal, have weak muscles, are easily fatigued, and exhibit a stiff, waddling gait. Epiphyseal dysplasia is a not uncommon disorder in which the ends of bones (the epiphyses) in children grow and ossify very slowly; dwarfing is a common result but may be limited to the lower limbs. Degenerative joint disease usually develops by middle age, but individuals may be otherwise healthy. Stippled epiphyses (dysplasia epiphysealis punctata) is a very rare, little understood disorder in which spots of opaque material are observed in the epiphyseal cartilage at birth. Many infants die within the first year; those who live may show dwarfism, mental retardation, and congenital cataracts. Metaphyseal dysplasia is a very rare, familial disorder in which the cortex of the shafts of long bones is thin and tends to fracture; affected persons may be otherwise healthy. Hip dysplasia is a hereditary condition in dogs, especially in large breeds such as the German shepherd, Old English sheepdog, and St. Bernard. It includes a range of abnormalities involving the head of the thigh bone and the receiving socket in the hip bone.