An 8-year-old male child born to nonconsanguineous parents came to us, with a 2 months history of progressively increasing jerky movements of body and limbs. This began on right leg, as sudden flexor spasms of the foot while walking, which led to frequent falling. In 2 weeks' time, it increased in frequency and spread to right thigh muscles as flexion contractions of the hip. By 11/2 months, trunk muscles and upper limbs were also affected. Extensor spasms predominated in trunk muscles which resulted in frequent prolonged arching back of the body. Due to these myoclonic contractions he could not sit or handle things. Spasms were painful, present during rest, increased by activity, touch, loud sound, and disappeared in sleep. His sensorium was normal. He had no difficulty in chewing or swallowing food. No bowel or bladder retention or incontinence. No sensory involvement. He developed oliguria and high colored urine in the last 1-week. No history of any serotoninergic or antidopaminergic drug intake and no difficulty in opening mouth.
During examination, he had very frequent, violent myoclonic jerks of trunk and limbs. Due to severe lordosis he could not lie supine. He was in agonizing pain during the spasms and had visible severe wasting. Pulse rate 83/min, blood pressure 130/76 mmHg, respiratory rate 18/min, and had mild pedal edema. There were multiple pressure sores on areas where there was frequent rubbing of the skin. Higher mental functions and cranial nerves were within normal limits. Muscle tone was increased and passive movements were difficult.
Superficial reflexes were normal including flexor plantar. Deep tendon reflexes were brisk. All sensations were normally appreciated. No cerebellar signs. Skull and spine were normal. Fundus examination revealed no abnormality. We made a provisional diagnosis of subacute encephalomyelitis and myoglobin mediated acute tubular necrosis with differential diagnosis of SPS and progressive myoclonic epilepsy.
His blood counts, serum calcium, thyroid function, blood sugar, glucose tolerance test, and tuberculosis screening, were within normal limits. Magnetic resonance imaging brain, spine, and electroencephalography (EEG) also were normal. Investigation results, which were abnormal, are given in the Table 1. X-ray chest, ultrasound sonography abdomen did not reveal lymphadenopathy or other neoplastic lesions. All investigations were sent in the first 2 days of admission based on the initial differential diagnosis.
He was treated with alkalinization and potassium lowering agents. Renal function started improving from next day. Methylprednisolone intravenous (IV) was given for 5 days along with clonazepam and valproate. Since there was no improvement, IV immunoglobulin (IVIG) was given for 5 days. There was no change in myoclonus. By then, the result of CSF autoantibody GAD65 came as positive. Hence, he was started on IV rituximab 375 mgm/m2/week. After the second dose of rituximab, myoclonus decreased significantly, he started sitting comfortably and began walking with little support in the next 7 days.
His renal function completely returned to normal. A total of 4 doses of rituximab was given at weekly intervals. He was discharged on oral tapering dose of prednisolone, clonazepam, and sodium valproate. He was doing well at 1-month follow-up visit. His muscle spasms had completely subsided.