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): Gene(s) directly associated with this condition or phenotype.	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
Symptoms of distal hereditary motor neuropathy, type V usually begin during adolescence, but onset varies from infancy to the mid-thirties. Cramps in the hand brought on by exposure to cold temperatures are often the initial symptom.

The characteristic features of distal hereditary motor neuropathy, type V are weakness and wasting (atrophy) of muscles of the hand, specifically on the thumb side of the index finger and in the palm at the base of the thumb. Foot abnormalities, such as a high arch (pes cavus), are also common, and some affected individuals eventually develop problems with walking (gait disturbance). People with this disorder have normal life expectancies.

Distal hereditary motor neuropathy, type V is a progressive disorder that affects nerve cells in the spinal cord. It results in muscle weakness and affects movement of 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.

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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.

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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).

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Decreased patellar reflex

MedGen UID:: 478814
•Concept ID:: C3277184
•: Finding

Decreased intensity of the patellar reflex (also known as the knee jerk reflex).

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Decreased motor nerve conduction velocity

MedGen UID:: 388130
•Concept ID:: C1858729
•: Finding

A type of decreased nerve conduction velocity that affects the motor neuron.

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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).

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Thenar muscle atrophy