I was wondering if someone could help me with the distinction between MMD1 and MMD2?  The person I care for has mental retardation and very slow progression of this disease. Does it make a difference in treatment options? Thanks! 

Congenital DM1. A transmission ratio distortion at conception favors transmission of larger CTG repeats than those present in the parent [Dean et al 2006]. The mother is almost always the parent who transmits the larger repeat, but transmission by the father has been reported [Zeesman et al 2002]. Presence of a large repeat may lead to earlier onset and more severe disease, known as congenital DM1 [De Temmerman et al 2004, Rakocevic-Stojanovic et al 2005].

Congenital DM1 often presents before birth as polyhydramnios (excess amniotic fluid) and reduced fetal movement.

After delivery, the main features are severe generalized weakness, hypotonia, and respiratory compromise. Typically, affected infants have an inverted V-shaped (also termed 'tented or 'fish'-shaped) upper lip, which is characteristic of significant facial diplegia (weakness). Mortality from respiratory failure is high.

Surviving infants experience gradual improvement in motor function. Affected children are usually able to walk; however, a progressive myopathy occurs eventually, as in the classic form [Joseph et al 1997].

Mental retardation is present in 50%-60% of individuals with congenital DM1. The cause of the mental retardation is unclear, but cerebral atrophy and ventricular dilation are often evident at birth. Mental retardation may result from a combination of early respiratory failure and a direct effect of the DMPK mutation on the brain [Spranger et al 1997, Ashikawa 1998].

Neuropathology. Brain neurons may contain tau-associated neurofibrillary tangles [Maurage et al 2005, Oyamada et al 2006].