MedGen

Autosomal dominant distal hereditary motor neuronopathy-13 (HMND13) is a neurologic disorder characterized by distal muscle weakness and atrophy affecting both the upper and lower limbs, resulting in difficulty walking and poor fine hand motor skills. Some patients show spasticity and hyperreflexia, mainly of the lower limbs: these features overlap with those observed in Silver syndrome, an allelic disorder. In addition, some patients with BSCL2 mutations show features of Charcot-Marie-Tooth type 2 (CMT2) with distal sensory impairment. HMND13, Silver syndrome (SPG17), and features of axonal sensorimotor peripheral neuropathy (CMT2) thus represent a phenotypic spectrum associated with heterozygous mutations in the BSCL2 gene. Individuals with the same mutation may manifest features consistent with any of those disorders; variability is even observed within the same family (summary by Van de Warrenburg et al., 2006; Luigetti et al., 2010; Choi et al., 2013). For a general phenotypic description and a discussion of genetic heterogeneity of distal HMN, see HMND1 (182960). [from OMIM]

Amyotrophic lateral sclerosis-28 (ALS28) is an autosomal dominant neurodegenerative disorder characterized by adult onset of slowly progressive limb muscle weakness and atrophy resulting in gait difficulties, loss of ambulation, and distal upper limb weakness. Facial involvement is rare, but some patients may have respiratory insufficiency. EMG and muscle biopsy show active and chronic denervation. Patient-derived motor neurons show accumulation of TDP43 (605078) and toxic intranuclear RNA accumulation (Kume et al., 2023). For discussion of genetic heterogeneity of amyotrophic lateral sclerosis, see ALS1 (105400). [from OMIM]

A diagnostic reflex elicited by stimulation of the skin over the surface of the lateral malleolus of the foot. The Chaddock refelx is present if there is extension of one or more or all of the toes with or without fanning of them when the external inframalleolar skin is stimulated. The Chaddock sign, similar to the Babinski sign, is taken to be an indication of disease of the spinocortical (pyramidal) tract. [from HPO]