The family was later reported as having a form of peroneal muscular atrophy. The term "hereditary sensory neuropathy" (HSN) was first used by Hicks to describe a family with associated spontaneous shooting pains and deafness. The described syndrome was caused by toxic sphingolipids and sensory involvement was demonstrated thus, it was most likely a severe early-onset form of HSN. (One individual, described by Suh et al, was reported to have skin ulceration.)Īn individual with pathogenic variant p.Ser331Tyr was included in a description of SPTLC1-related juvenile ALS by Johnson et al. The general absence of skin ulceration in these severe childhood-onset neuropathies may be explained by slow accumulation of toxic sphingolipids. Disease is caused by accumulation of toxic sphingolipids. Affected individuals have muscle atrophy (which may include atrophy of the tongue), hypotonia, growth deficiency, intellectual disability (in some individuals), cataracts, and laryngeal involvement. SPTLC1 pathogenic variants at Ser331, including p.Ser331Phe and p.Ser331Tyr, are associated with severe childhood-onset motor and sensory neuropathy (generally without skin ulceration as in classic HSAN1A). Įlectrophysiology is initially normal and is not useful for early detection. Visceral autonomic features are rare, with abdominal pain, diarrhea, and weight loss reported in some individuals in one family only. Rarely, pupillary abnormalities termed "tonic pupils" or pseudo-Argyll-Robertson pupils (i.e., those not associated with syphilis) are present. When present, its onset is in middle to late adulthood. Corticospinal degeneration was not observed on an autopsy of an individual with SPTLC1-related HSN, but data are limited. Retained and even brisk proximal reflexes in some affected individuals may indicate some upper motor neuron involvement. Older affected individuals may require a wheelchair for mobility. The weakness of ankle flexors produces a floppy, flipper-like foot rather than pes cavus.Ī few instances of early severe motor involvement have been reported. Distal muscle weakness and wasting are present in all advanced cases. Weakness commences in the distal lower limbs, followed by the distal upper limbs and in severe cases, proximal upper- and lower-limb girdle muscles. If the sensory loss is unheeded, chronic ulcerations of the extremities may lead to osteomyelitis and require amputations. Shooting pains may be a distinctive but variable feature of SPTLC1-related HSN. Later, positive sensory phenomena occur (numbness, paresthesia, burning, and shooting pains). Onset ranges from the teens to the sixth decade. SPTLC1-related hereditary sensory neuropathy (HSN) is usually first noticed when painless injuries appear.
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