A jaw abnormality is a disorder in the formation, shape and/or size of the jaw. In general abnormalities arise within the jaw when there is a disturbance or fault in the fusion of the mandibular processes. The mandible in particular has the most differential typical growth anomalies than any other bone in the human skeleton. This is due to variants in the complex symmetrical growth pattern which formulates the mandible.The mandible in particular plays a significant role in appearance as it is the only moving part of the facial skeleton. This has a large impact upon an individuals’ ability speak, masticate and also influence their overall aesthetic and expressive features of the face. In turn the maxilla faces the same issues if any abnormalities in size or position were to occur. The obvious functional disabilities that arise from jaw abnormalities are very much physically seen as previously stated, but when considering these individuals it must be kept in mind that these conditions may well affect them psychologically; making them feel as though they are handicapped. It is also of the utmost importance when correcting these mandibular anomalies that the teeth result in a good occlusion with the opposing dentition of the maxilla. If this is not done satisfactorily occlusal instability may be created leading to a plethora of other issues. In order to correct mandibular anomalies it is common for a complex treatment plan which would involve surgical intervention and orthodontic input.
This maybe because a posterior placing of the condylar head with regard to the skull or to a steep mandibular angle resulting in an evident jaw retrusion. The acquired type of micrognathia occurs after birth and usually is an effect of a disturbance to temporomandibular joint. Growth of mandible depends on the normally developing condyles and the muscle function For example, trauma or infection that affect mastoid, middle ear or the joint will result in ankylosis of temporomandibular joint leading to mandibular micrognathia. MacronagthiaMacronagthia is a condition of abnormally large jaws. The jaw size is usually proportion to the increase in skeleton size. It is usually due to excessive growth of the mandible and can have features including reverse maxillary to mandibular relationship, reverse overjet or absence of overbite. It can also be clinically presented when the glenoid fossa and condylar head is more anteriorly placed, causing mandibular prognathism. Macronagthism can be associated with other medical conditions :-
1. Pagets disease where there is overgrowth of the maxilla, cranium and mandible2. Acromegaly, an endocrine disease, can present with enlargement of bones with growth potential such as the mandible, thickened soft tissues and facial features and spade-like hands 
Macrogenia or MicrogeniaMacrogenia and microgenia occur when there is a normal skeletal relationship but the chin, skeletal and soft tissue components, failed to develop in proportion to the skeletal base, resulting in marked protrusive (macrogenia) or retrusive (microgenia) facial profile.