- Decreased motor nerve conduction velocity (HP:0003431): A type of decreased nerve conduction velocity that affects the motor neuron. Evidence: PCS. Frequency: 20/20. (PMID:7693129)
- Steppage gait (HP:0003376): An abnormal gait pattern that arises from weakness of the pretibial and peroneal muscles due to a lower motor neuron lesion. Affected patients have footdrop and are unable to dorsiflex and evert the foot. The leg is lifted high on walking so that the toes clear the ground, and there may be a slapping noise when the foot strikes the ground again. Evidence: IEA. (OMIM:118200)
- Ulnar claw (HP:0001178): An abnormal hand position characterized by hyperextension of the fourth and fifth fingers at the metacarpophalangeal joints and flexion of the interphalangeal joints of the same fingers such that they are curled towards the palm. Evidence: IEA. (OMIM:118200)
- Distal amyotrophy (HP:0003693): Muscular atrophy affecting muscles in the distal portions of the extremities. Evidence: PCS. Frequency: 30/30. (OMIM:118200;PMID:7693129)
- Distal muscle weakness (HP:0002460): Reduced strength of the musculature of the distal extremities. Evidence: PCS. Frequency: 20/20. (PMID:7693129)
- Limb muscle weakness (HP:0003690): Reduced strength and weakness of the muscles of the arms and legs. Evidence: TAS. (OMIM:118200)
- Split hand (HP:0001171): A condition in which middle parts of the hand (fingers and metacarpals) are missing giving a cleft appearance. The severity is very variable ranging from slightly hypoplastic middle fingers over absent middle fingers as far as oligo- or monodactyl hands. Evidence: TAS. (OMIM:118200)
- Tonic pupil (HP:0012074): An abnormality of the pupillary light reaction characterized by a marked slowing of the light reaction of usually just one pupil. The pupil tends to be relatively dilated, and there is reduced accommodation. Evidence: TAS. (OMIM:118200)
- Foot dorsiflexor weakness (HP:0009027): Weakness of the muscles responsible for dorsiflexion of the foot, that is, of the movement of the toes towards the shin. The foot dorsiflexors include the tibialis anterior, the extensor hallucis longus, the extensor digitorum longus, and the peroneus tertius muscles. Evidence: IEA. (OMIM:118200)
- Distal sensory impairment (HP:0002936): An abnormal reduction in sensation in the distal portions of the extremities. Evidence: PCS. Frequency: 20/20. (PMID:7693129)
- Cold-induced muscle cramps (HP:0003449): Sudden and involuntary contractions of one or more muscles brought on by exposure to cold temperatures. Evidence: IEA. (OMIM:118200)
- Hammertoe (HP:0001765): Hyperextension of the metatarsal-phalangeal joint with hyperflexion of the proximal interphalangeal (PIP) joint. Evidence: IEA. (OMIM:118200)
- Hyporeflexia (HP:0001265): Reduction of neurologic reflexes such as the knee-jerk reaction. Evidence: IEA. (OMIM:118200)
- Kyphoscoliosis (HP:0002751): An abnormal curvature of the spine in both a coronal (lateral) and sagittal (back-to-front) plane. Evidence: PCS. Frequency: Frequent (HP:0040282). (OMIM:118200)
- Myelin outfoldings (HP:0004336): The presence of excessive redundant myelin in the peripheral nerve sheath. Evidence: IEA. (OMIM:118200)
- Insidious onset (HP:0003587): Gradual, very slow onset of disease manifestations. Evidence: IEA. (OMIM:118200)
- Juvenile onset (HP:0003621): Onset of signs or symptoms of disease between the age of 5 and 15 years. Evidence: PCS. (OMIM:118200)
- Pes cavus (HP:0001761): 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). Evidence: PCS. Frequency: 20/20. (PMID:7693129)
- Onion bulb formation (HP:0003383): Repeated episodes of segmental demyelination and remyelination lead to the accumulation of supernumerary Schwann cells around axons, which is referred to as onion bulb formation. This finding affects peripheral nerves. Evidence: IEA. (OMIM:118200)
- Areflexia (HP:0001284): Absence of neurologic reflexes such as the knee-jerk reaction. Evidence: TAS. Frequency: 30/30. (OMIM:118200;PMID:7693129)
- Hypertrophic nerve changes (HP:0003382). Evidence: IEA. (OMIM:118200)
- Decreased number of peripheral myelinated nerve fibers (HP:0003380): A loss of myelinated nerve fibers in the peripheral nervous system (in general, this finding can be observed on nerve biopsy). Evidence: IEA. (OMIM:118200)
- Peripheral demyelination (HP:0011096): A loss of myelin from the internode regions along myelinated nerve fibers of the peripheral nervous system. Evidence: PCS. Frequency: Frequent (HP:0040282). (OMIM:118200)
- Peripheral neuropathy (HP:0009830): Peripheral neuropathy is a general term for any disorder of the peripheral nervous system. The main clinical features used to classify peripheral neuropathy are distribution, type (mainly demyelinating versus mainly axonal), duration, and course. Evidence: TAS. (OMIM:118200)
- Autosomal dominant inheritance (HP:0000006): A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in heterozygotes. In the context of medical genetics, an autosomal dominant disorder is caused when a single copy of the mutant allele is present. Males and females are affected equally, and can both transmit the disorder with a risk of 50% for each child of inheriting the mutant allele. Evidence: PCS. (PMID:7693129)
- Slowly progressive (HP:0003677): Applies to a disease manifestation that only slowly increases in scope or severity over the course of time. Evidence: IEA. (OMIM:118200)
These phenotypes are associated with the disease Charcot-Marie-Tooth disease type 1B (OMIM:118200).