Hereditary sensory and autonomic neuropathies (HSN/HSAN) are clinically and genetically heterogeneous disorders of the peripheral nervous system that predominantly affect the sensory and autonomic neurons (Auer-Grumbach, 2013; pubmed:23931820).

Hereditary sensory and autonomic neuropathies (HSANs) occur much less frequently than do the primary hereditary motor sensory neuropathies (HMSNs) (http://www.uptodate.com/contents/hereditary-sensory-and-autonomic-neuropathies).

The hereditary sensory and autonomic neuropathies (HSAN), which are also referred to as hereditary sensory neuropathies (HSN), are a genetically and clinically heterogeneous group of disorders associated with sensory dysfunction, typically characterized by characterized by insensitivity to pain and resulting in injury to the fingers, tongue, lips, and other distal appendages. [from MIM:162400, MIM:616488; 2017.07.10]

HSAN2 is characterized by progressively reduced sensation to pain, temperature, and touch. Onset can be at birth and is often before puberty. The sensory deficit is predominantly distal with the lower limbs more severely affected than the upper limbs. Over time sensory function becomes severely reduced. Unnoticed injuries and neuropathic skin promote ulcerations and infections that result in spontaneous amputation of digits or the need for surgical amputation. [Gene Reviews, Hereditary Sensory and Autonomic Neuropathy Type II; 2018.08.21]

HSN2C is an autosomal recessive disorder characterized by onset in the first decade of progressive distal sensory loss leading to ulceration and amputation of the fingers and toes. Affected individuals also develop distal muscle weakness, primarily affecting the lower limbs (summary by Riviere et al., 2011; pubmed:21820098). [from MIM:614213; 2018.08.21]