Autosomal recessive distal hereditary motor neuropathies

Hereditary motor neuronopathies form a group of heterogeneous disorders, the cardinal symptom of which is loss of motor function due to muscle weakness and atrophy. The initial distribution of weakness depends on type of hereditary motor neuronopathies and may be predominantly distal or proximal in the upper and/or lower limbs or bulbar. The mode of inheritance is either autosomal dominant, autosomal recessive or rarely X-linked. In 1993 Harding classified hereditary motor neuronopathies according to clinical picture, age of onset and type of inheritance. The distal form of hereditary motor neuronopathies is one subgroup with four autosomal dominant forms and three autosomal recessive forms (I-VII). The three autosomal recessive forms are: a. type III, a mild juvenile disorder with a relatively benign course; b. type IV, a severe juvenile disorder causing disability early in life; and c. type VI, a severe infantile disorder with an age of onset in infancy, a rapid progression of the disease and early death. Recently we have, identified a novel form of autosomal recessive distal hereditary motor neuronopathies (HMN-J) in a cluster of 27 patients originating from the Jerash region of Jordan. The clinical picture of patients is: age of onset 6-10 years, with distal weakness and wasting in legs, and within 2 years, involvement of the distal upper limb muscles. At the early stages of disease pyramidal features are present. The clinical picture of patients and laboratory findings - including neurophysiology studies, biopsies of sural nerve and muscle and genetic analysis of families - will be discussed.