Periodic Febrile Encephalopathy with Mixed Connective Tissue Disease: a Novel Phenotype?

Abstract

Activation of the innate immune system due to single gene mutations is a hallmark of the autoinflammatory syndromes. Typically, these disorders are not associated with autoimmune phenomena. Here we describe a Caucasian male with a complex phenotype comprising features of both an autoinflammatory state and autoimmunity. He had a life-long history of recurrent encephalopathic episodes during which fever, anorexia and drowsiness would develop over a period of a few hours and last for up to seven days. His phenotype was additionally characterised by a mixed connective tissue disorder with an inflammatory arthritis, restrictive lung disease and variably elevated autoantibodies. Furthermore, he experienced autoimmune thrombocytopenia, gastro-intestinal bleeding and epilepsy on a background of mild to moderate intellectual compromise. Radiological examination demonstrated periarticular, subcutaneous soft tissue and intracranial calcification, together with cerebellar vermis hypoplasia. EEG showed features of a generalised epilepsy. All other investigations were essentially non-contributory. He died at 19 years of age of acute respiratory failure secondary to restrictive lung disease and pneumonia. We hypothesise that this phenotype represents a previously undescribed autoinflammatory syndrome, with secondary autoimmune sequelae.