Chondrocalcinosis, or cartilage calcification, is a common condition that usually results from deposition of crystals of calcium pyrophosphate dihydrate (CPPD) in articular hyaline and fibro-cartilage. CPPD crystal deposition may be asymptomatic or associated with characteristic acute attacks ('pseudogout') or chronic arthritis. It can be detected radiographically. Chondrocalcinosis occurs in 3 forms: a primary hereditary form (e.g., CCAL2); a form associated with metabolic disorders (e.g., hyperparathyroidism, hemochromatosis, and hypomagnesemia); and a sporadic form, which may in some cases represent the hereditary form (summary by Hughes et al., 1995 and Richette et al., 2009). Genetic Heterogeneity of Chondrocalcinosis Another form of chondrocalcinosis (CCAL1; 600668) has been mapped to chromosome 8q.

Autosomal dominant craniometaphyseal dysplasia (designated AD-CMD in this review) is characterized by progressive diffuse hyperostosis of cranial bones evident clinically as wide nasal bridge, paranasal bossing, widely spaced eyes with an increase in bizygomatic width, and prominent mandible. Development of dentition may be delayed and teeth may fail to erupt as a result of hyperostosis and sclerosis of alveolar bone. Progressive thickening of craniofacial bones continues throughout life, often resulting in narrowing of the cranial foramina, including the foramen magnum. If untreated, compression of cranial nerves can lead to disabling conditions such as facial palsy, blindness, or deafness (conductive and/or sensorineural hearing loss). In individuals with typical uncomplicated AD-CMD life expectancy is normal; in those with severe AD-CMD life expectancy can be reduced as a result of compression of the foramen magnum.