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Neuronopathy, distal hereditary motor, type 5B(HMN5B; DSMAVB; DHMN5B; HMND12)

MedGen UID:
766570
Concept ID:
C3553656
Disease or Syndrome
Synonyms: DHMN VB; HMN VB; NEURONOPATHY, DISTAL HEREDITARY MOTOR, HARDING TYPE VB; NEUROPATHY, DISTAL HEREDITARY MOTOR, HARDING TYPE VB; SPINAL MUSCULAR ATROPHY, DISTAL, HARDING TYPE VB
 
Gene (location): REEP1 (2p11.2)
 
Monarch Initiative: MONDO:0013884
OMIM®: 614751

Definition

Autosomal dominant distal hereditary motor neuronopathy-12 (HMND12) is a neurologic disorder characterized by onset in the first or second decade of distal muscle weakness and atrophy, primarily affecting the intrinsic hand muscles, but also affecting the lower legs, resulting in abnormal gait and pes cavus (summary by Beetz et al., 2012). For a discussion of genetic heterogeneity of autosomal dominant distal HMN, see HMND1 (182960). [from OMIM]

Additional description

From MedlinePlus Genetics
People with distal hereditary motor neuropathy, type V can have exaggerated reflexes (hyperreflexia) or other disturbances in the nerves that are used to detect sensations (sensory neuropathy). Although sensory neuropathy is uncommon in people with distal hereditary motor neuropathy, type V, it is typical of a disorder called Charcot-Marie-Tooth disease. These two disorders have overlapping features and can also share a genetic cause. People with distal hereditary motor neuropathy, type V typically have a normal life expectancy.

About half of individuals with distal hereditary motor neuropathy, type V develop muscle weakness in the feet and lower legs. This can lead to problems with walking (gait disturbance), difficulty lifting the front part of the foot (foot drop), and a high foot arch (pes cavus).

The characteristic features of distal hereditary motor neuropathy, type V are weakness and wasting (atrophy) of muscles of the hand, specifically on the side of the index finger near the thumb and in the palm of the hand at the base of the thumb.

Signs and symptoms of distal hereditary motor neuropathy, type V usually begin during adolescence, but they can appear any time between infancy and the mid-30s. The first symptom of this condition is often cramps in the hands that are brought on by exposure to cold temperatures.

Distal hereditary motor neuropathy, type V is a disorder that affects nerve cells (neurons) in the spinal cord. This condition specifically affects motor neurons, which are specialized cells that control muscle movement. Damage to motor neurons results in muscle weakness that worsens over time. In people with distal hereditary motor neuropathy, type V, this weakness primarily affects movement in the muscles that are furthest from the center of the body (distal muscles), such as the muscles in the hands and feet.  https://medlineplus.gov/genetics/condition/distal-hereditary-motor-neuropathy-type-v

Clinical features

From HPO
Peroneal muscle weakness
MedGen UID:
488803
Concept ID:
C0240733
Finding
Weakness of the peroneal muscles.
Absent Achilles reflex
MedGen UID:
108240
Concept ID:
C0558845
Finding
Absence of the Achilles reflex (also known as the ankle jerk reflex), which can normally be elicited by tapping the tendon is tapped while the foot is dorsiflexed.
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).
Decreased patellar reflex
MedGen UID:
478814
Concept ID:
C3277184
Finding
Decreased intensity of the patellar reflex (also known as the knee jerk reflex).
Decreased motor nerve conduction velocity
MedGen UID:
388130
Concept ID:
C1858729
Finding
A type of decreased nerve conduction velocity that affects the motor neuron.
Peroneal muscle atrophy
MedGen UID:
810815
Concept ID:
C1389118
Disease or Syndrome
Atrophy of the peroneous muscles, peroneus longus (also known as Fibularis longus), Peroneus brevis (also known as fibularis brevis, and Peroneus tertius (also known as fibularis tertius).
Thenar muscle atrophy
MedGen UID:
355274
Concept ID:
C1864715
Finding
Wasting of thenar muscles, which are located on palm of the hand at the base of the thumb.

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