Familial Madras motor neuron disease (FMMND): Study of 15 families from southern India

Madras motor neuron disease (MMND) and Madras motor neuron disease variant (MMNDV) have an unique geographic distribution with concentration of majority of cases in the southern states of India. They have the characteristic features of onset in young, weakness and wasting of the limbs, multiple cranial nerve palsies particularly involving the 7th, 9th to 12th and sensorineural hearing impairment. In addition, all patients with MMNDV have bilateral optic atrophy. During the past 32 years, a total of 104 patients were diagnosed to have MMND and among these 25 patients with the familial form were further evaluated. In this report, we describe the clinical features of these 25 patients diagnosed to have familial Madras motor neuron disease (FMMND) or familial Madras motor neuron disease variant (FMMNDV), belonging to 15 families hailing from southern India. There were 10 patients diagnosed to have FMMND and 15 with FMMNDV. There were 14 males and 11 females with mean age at onset of 13.0 ± 6.2 years and mean duration of illness of 73.6 ± 74.0 months. Notably, the occurrence of MMNDV in the familial group (15 of 25 patients) was significantly more as compared to occurrence in the group with sporadic MMND (SMMND) [12 of 79 patients] (p = 0.0002).