[Seronegative myasthenia gravis associated with other autoimmune diseases]. / Miastenia gravis seronegativa asociada a otras enfermedades autoinmunes.

INTRODUCTION: The presence of muscle-specific receptor tyrosine kinase (MuSK) defines a subset of patients with generalized myasthenia gravis. The diagnosis of this disease, due to its clinical distribution and negativity of the acetylcholine receptor (AchR) antibodies, is mo re complicated, especially when linked to other autoimmune diseases. CASE REPORT: A 41 year woman with 3 month long symptoms consisting in diplopia, dysarthria and gait instability. On examination, only mild paresis of the right external rectus without fatigability. The complementary tests performed were evoked potentials were normal including multimodal except for the brain magnetic resonance imaging that detected six-eight hyperintense periventricular nodular lesions in both semioval centers, with impairment of corona radiata and corpus callosum without contrast uptake. Given these findings, she was diagnosed of demyelinating disease and treated with megadoses of methylprednisolone for 5 days with mild clinical improvement. At one month, her condition deteriorated, presenting dysphagia and respiratory failure. The neurophysiological study was extended, and very pathological Jitter was detected in the frontal muscle. Despite the negative AchR antibodies, treatment was initiated with pyridostigmine bromide with poor response, admission to the intensive care unit and plasmapheresis due to a new respiratory episode being required. The torpid course and positive outcome of the MuSK antibodies have confirmed the diagnosis. CONCLUSIONS: The detection of these antibodies and performance of neurophysiological tests in clinically deficient muscles are required for the diagnosis of these clinical forms, especially when the neuroimaging-based pathological findings do not justify the clinical course of the patient.

[Encephalitis caused by Rickettsia conorii without exanthema]. / Encefalitis por Rickettsia conorii sin exantema.

INTRODUCTION: Mediterranean boutonneuse fever, caused by Rickettsia conorii, is an endemic disease in the Mediterranean area. The serious forms of the disease, which include encephalitis, are infrequent but are associated with a high mortality rate. Diagnostic suspicion is backed up by the development of exanthema. We report the case of a patient who developed encephalitis caused by Rickettsia conorii without exanthema. Clinical case. A 27 year old woman who had nauseas, headache, fever, abdominal upset and generalised pain during the days before being admitted to hospital. On the day she was admitted, she noticed reduced strength in the left limbs, together with numbness and pins and needles in the left side of the body. In the casualty department she presented tonic seizures in the left extremities and later generalised tonic clonic seizures. Exploration showed facial paresis and 4/5 hemiparesis on the left side. Complementary tests carried out in casualty, including cerebrospinal fluid (CSF), did not reveal any significant findings. She was admitted after a loading dose of phenytoin. After 48 hours she presented fever and repeated complex partial seizures. A new CSF analysis was normal. She was treated with valproate, clonazepam, ceftriaxone, doxycycline and acyclovir. An electroencephalogram (EEG) showed theta activity in the left centroparietal areas and slow delta waves in the right temporal regions. Magnetic resonance imaging (MRI) of the brain showed contrast enhancement in the meninges. 24 later, due to the frequency of the seizures, phenobarbital and methylprednisolone were added, which enabled the seizures to be controlled. The posterior brain MRI revealed a right parasylvian lesion. Serological Rickettsia conorii IgM +, IgG 1/256 was administered. After eight months, she has presented no seizures or neurological deficit. CONCLUSIONS: There are cases of encephalitis from Rickettsia conorii that can present without exanthema. This means that in endemic areas early treatment with doxycycline could be advisable when faced with encephalitis of unknown aetiology, bearing in mind the high mortality rate that occurs when no early treatment is administered and the good tolerance to doxycycline.