This causes the number of repeats to change in successive generations, such that an unaffected parent with an "intermediate" number of repeats (28–35), or "reduced penetrance" (36–40), may pass on a copy of the gene with an increase in the number of repeats that produces fully penetrant HD. The earlier age of onset and greater severity of disease in successive generations due to increases in the number of repeats is known as genetic anticipation. Instability is greater in spermatogenesis than oogenesis; maternally inherited alleles are usually of a similar repeat length, whereas paternally inherited ones have a higher chance of increasing in length. Rarely is Huntingtons disease caused by a new mutation, where neither parent has over 36 CAG repeats.In the rare situations where both parents have an expanded HD gene, the risk increases to 75%, and when either parent has two expanded copies, the risk is 100% (all children will be affected). Individuals with both genes affected are rare. For some time, HD was thought to be the only disease for which possession of a second mutated gene did not affect symptoms and progression, but it has since been found that it can affect the phenotype and the rate of progression. Mechanisms
Huntingtin protein interacts with over 100 other proteins, and appears to have multiple functions. The behavior of the mutated protein (mHtt) is not completely understood, but it is toxic to certain cell types, particularly brain cells.
Perichondritis  is inflammation of the perichondrium, a layer of connective tissue which surrounds cartilage. A common form, auricular perichondritis (perichondritis auriculae) involves infection of the pinna due to infection of traumatic or surgical wound or the spread of inflammation into depth (e.g. Infected transcartilaginous ear piercings). It may lead to severe deformation of the pinna if not treated vigorously with IV antibiotics. The causative organism is usually Pseudomonas aeruginosa. A rare form is laryngeal perichondritis (perichondritis laryngis). It develops suddenly due to an injury, virulent organisms or compromised immune status of the host, and also affects cartilage of the larynx. This may result in deformations and stenoses. Signs and symptoms
Signs of perichondritis or  chondritis  in  patients  with  an  embedded  earring  are  similar (these include pain, swelling and erythema of the overlying skin) and fluctuant swelling indicate an abscess that we should drain (typically associated with chondritis). Clinically, perichondritis can be differentiated from cellulitis of the pinna, in that the first usually does not involve the earlobe.In serious cases pus appears between the perichondrium and cartilage. Purulent melting of auricular cartilage takes place. Dead tissue tears away, as a result, auricle deforms strongly and becomes shrunken. See also
Chondritis

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