Hereditary neuralgic amyotrophy with predilection for the brachial plexus is an autosomal dominant disorder associated with recurrent, episodic, painful brachial neuropathies. Mildly dysmorphic facial features including hypotelorism, long nasal bridge and upslanting palpebral fissures are present in affected people in some pedigrees with this disease. The molecular basis of hereditary neuralgic amyotrophy is unknown and the specific gene which leads to it has not been identified. The feature of brachial neuropathy is shared with hereditary neuropathy with liability to pressure palsies, another autosomal dominant disorder which maps to chromosome 17p11.2-12 and may be clinically confused with hereditary neuralgic amyotrophy. Genetic studies have shown that the two diseases do not map to the same chromosomal region and are, therefore, genetically distinct disorders. Genetic linkage studies with polymerase chain reaction-based DNA markers in two large pedigrees recently localized the hereditary neuralgic amyotrophy gene to the distal long arm of chromosome 17 (17q24-qter).