Abstract
The hereditary sensory and autonomic neuropathies (HSAN) encompass a number of inherited disorders that are associated with sensory dysfunction (depressed reflexes, altered pain and temperature perception) and varying degrees of autonomic dysfunction (gastroesophageal reflux, postural hypotention, excessive sweating). Subsequent to the numerical classification of four distinct forms of HSAN that was proposed by Dyck and Ohta, additional entities continue to be described, so that identification and classification are ongoing. As a group, the HSAN are rare diseases that affect both sexes. HSAN III is almost exclusive to individuals of Eastern European Jewish extraction, with incidence of 1 per 3600 live births. Several hundred cases with HSAN IV have been reported. The worldwide prevalence of HSAN type II is very low. This review focuses on the description of three of the disorders, HSAN II through IV, that are characterized by autosomal recessive inheritance and onset at birth. These three forms of HSAN have been the most intensively studied, especially familial dysautonomia (Riley-Day syndrome or HSAN III), which is often used as a prototype for comparison to the other HSAN. Each HSAN disorder is likely caused by different genetic errors that affect specific aspects of small fiber neurodevelopment, which result in variable phenotypic expression. As genetic tests are routinely used for diagnostic confirmation of HSAN III only, other means of differentiating between the disorders is necessary. Diagnosis is based on the clinical features, the degree of both sensory and autonomic dysfunction, and biochemical evaluations, with pathologic examinations serving to further confirm differences. Treatments for all these disorders are supportive.
Highlights
Genetic disorders affecting the sensory and autonomic nervous systems are rare, their existence provides a means of furthering our knowledge regarding a very complex part of the nervous system
The close relationship between development and survival of the sensory and autonomic nervous system is especially well illustrated in the diversity of a group of genetic disorders known as Hereditary Sensory and Autonomic Neuropathies (HSAN) [1]
Familial dysautonomia (FD), originally the Riley Day syndrome [4], is referred to as HSAN III and hereditary sensory neuropathy with anhidrosis is referred to congenital insensitivity to pain with anhidrosis (CIPA) or HSAN IV (Table 1)
Summary
Genetic disorders affecting the sensory and autonomic nervous systems are rare, their existence provides a means of furthering our knowledge regarding a very complex part of the nervous system. As individuals affected with the other HSANs fail to produce an axon flare after intradermal histamine [1], careful assessment of the other clinical signs and symptoms is necessary in order to distinguish between these disorders. It may be confused with FD in the neonatal period but the differences become much clearer with time as the characteristic anhidrosis causes cutaneous changes and the sensory insensitivity is much more profound resulting in self-mutilation, auto-amputation, and corneal scarring [1,3,12,56,57]. Http://www.OJRD.com/content/2/1/39 ical features suggesting central involvement as the patients are frequently exhibit hypotonia and delayed developmental milestones in the early years and there can be severe learning problems, often associated with hyperactivity [1,12,58]. We anticipate that further improvement in prognosis will be based on increased understanding of specific gene actions that will lead to definitive therapies
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
