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Neuropathy, hereditary motor and sensory, type VIc, with optic atrophy(HMSN6C; CMT6C)

MedGen UID:
1680245
Concept ID:
C5193137
Disease or Syndrome
Synonyms: CHARCOT-MARIE-TOOTH DISEASE, TYPE 6C; HMSN VIC
 
Gene (location): PDXK (21q22.3)
 
Monarch Initiative: MONDO:0032792
OMIM®: 618511

Definition

Hereditary motor and sensory neuropathy type VIC with optic atrophy (HMSN6C) is an autosomal recessive axonal sensorimotor peripheral neuropathy characterized by progressive distal muscle weakness and atrophy primarily affecting the lower limbs. Onset of neuropathy is in the first decade, manifest by difficulty walking and running and followed by similar involvement of the upper limbs and hands. The disorder is associated with distal sensory impairment, particularly of position and vibration sense, as well as areflexia; individuals usually have pes cavus, hammertoes, and atrophy of the intrinsic hand muscles. In addition, progressive optic atrophy and visual impairment occur during adulthood. Treatment with pyridoxal 5-prime phosphate supplementation (vitamin B6) may result in amelioration of symptoms and slow progression of the disease (summary by Chelban et al., 2019). For a general phenotypic description and a discussion of genetic heterogeneity of HMSN6, see HMSN6A (601152). [from OMIM]

Clinical features

From HPO
Pes cavus
MedGen UID:
675590
Concept ID:
C0728829
Congenital Abnormality
An increase in height of the medial longitudinal arch of the foot that does not flatten on weight bearing (i.e., a distinctly hollow form of the sole of the foot when it is bearing weight).
Hammertoe
MedGen UID:
209712
Concept ID:
C1136179
Anatomical Abnormality
Hyperextension of the metatarsal-phalangeal joint with hyperflexion of the proximal interphalangeal (PIP) joint.
Upper limb muscle weakness
MedGen UID:
305607
Concept ID:
C1698196
Finding
Weakness of the muscles of the arms.
Lower limb muscle weakness
MedGen UID:
324478
Concept ID:
C1836296
Finding
Weakness of the muscles of the legs.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
Positive Romberg sign
MedGen UID:
66017
Concept ID:
C0240914
Finding
The patient stands with the feet placed together and balance and is asked to close his or her eyes. A loss of balance upon eye closure is a positive Romberg sign and is interpreted as indicating a deficit in proprioception.
Impaired pain sensation
MedGen UID:
373348
Concept ID:
C1837522
Finding
Reduced ability to perceive painful stimuli.
Impaired distal vibration sensation
MedGen UID:
381262
Concept ID:
C1853767
Finding
A decrease in the ability to perceive vibration in the distal portions of the limbs.
Lower limb amyotrophy
MedGen UID:
870475
Concept ID:
C4024921
Finding
Muscular atrophy affecting the lower limb.
Claw hand deformity
MedGen UID:
1814631
Concept ID:
C5702555
Anatomical Abnormality
An abnormality of the hand characterized by metacarpophalangeal (MCP) hyperextension and proximal interphalangeal (PIP) and distal interphalangeal (DIP) flexion. The position of the affected hand is said to resemble a claw.
Optic atrophy
MedGen UID:
18180
Concept ID:
C0029124
Disease or Syndrome
Atrophy of the optic nerve. Optic atrophy results from the death of the retinal ganglion cell axons that comprise the optic nerve and manifesting as a pale optic nerve on fundoscopy.
Color vision defect
MedGen UID:
115964
Concept ID:
C0234629
Finding
An anomaly in the ability to discriminate between or recognize colors.
Reduced visual acuity
MedGen UID:
65889
Concept ID:
C0234632
Finding
Diminished clarity of vision.
Optic disc pallor
MedGen UID:
108218
Concept ID:
C0554970
Finding
A pale yellow discoloration of the optic disc (the area of the optic nerve head in the retina). The optic disc normally has a pinkish hue with a central yellowish depression.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  

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