Stiff Person Syndrome or Stiff Man Syndrome as it was previously called. From the National Organization of Rare Disorder NORD :-
'Stiff-person syndrome (SPS) is a rare acquired neurological disorder characterized by progressive muscle stiffness (rigidity) and repeated episodes of painful muscle spasms. Muscular rigidity often fluctuates (i.e., grows worse and then improves) and usually occurs along with the muscle spasms. Spasms may occur randomly or be triggered by a variety of different events including a sudden noise or light physical contact. In most cases, other neurological signs or symptoms do not occur. The severity and progression of SPS varies from one person to another. If left untreated, SPS can potentially progress to cause difficulty walking and significantly impact a person's ability to perform routine, daily tasks. Although the exact cause of SPS is unknown, it is believed to be an autoimmune disorder and sometimes occurs along with other autoimmune disorders.
Stiff-person syndrome has been described in the medical literature under many different, confusing names. Originally described as stiff-man syndrome, the name was changed to reflect that the disorder can affect individuals of any age and of either gender. In fact, most individuals with the condition are women. Stiff-person syndrome is considered by many researchers to be a spectrum of disease ranging from the involvement of just one area of the body to a widespread, rapidly progressive form that also includes involvement of the brain stem and spinal cord (progressive encephalomyelitis with rigidity and myoclonus).'
An all body stiffness was one of my many symptoms which lasted years. The worst was that of rigidity on waking with a reduction in symptoms when painfully flexing every joint large and small. Once diagnosed with Lyme Disease and given long term antibiotics this stiffness gradually went away. I had always assumed it was something vascular maybe inflammation but was interested to read information on SPS and see the two studies published which associated Stiff Man Syndrome with Neuroborreliosis, Lyme Disease.
[Syndromes of continuous muscular activity: report of a central case (stiff-man) and a peripheral case (neuromyotonia) associated with neuroborreliosis].
We describe two cases of continuous muscular activity: one which is central (the stiff-man syndrome), and another which is peripheral (neuromiotony), the latter in a patient suffering from diabetic neuropathy and with positive Borrellia burgdorferi serology in the bloodstream, as well as CSF. Both cases reacted favourably to medical treatment. In the first case botulinic toxin was used as a simultaneous treatment for focal pseudodystonia in one foot. Response was good.
Eight weeks after a tick bite, a 33-year-old male patient presented with stiffness of one leg together with spasmodic painful jerks resembling stiff man syndrome. Isolated myelitis of lumbosacral segments of the spinal cord, apparently confined to the grey matter, was diagnosed and its spirochaetal aetiology confirmed by serology and CSF findings. Oligoclonal IgG bands in CSF specific for Borrelia burgdorferi were found. Thus, there is evidence that B. burgdorferi ist able to cause a localized myelitis, probably of spinal interneurons, presenting as a partial stiff man syndrome.