SUN-155 A Complex Case of Adrenal Insufficiency Associated with NLRP1 Gene Mutation in a Patient with Myopathy and Mitochondrial Cytopathy

Abstract

Most cases of Addison’s disease are due to an autoimmune response, with the most commonly associated genes belonging to human leukocyte antigen (HLA) complex. Genome wide association studies have shown a significant association of variants of Nuclear Localization Leucine-Rich-Repeat Protein 1 (NLRP1) with Addison’s disease. NLRP1 protein is involved in the assembly of inflammasome which promotes the secretion of interleukin-1β, interleukin-18 and downstream inflammatory responses to regulate inflammation. With underlying myopathy and mitochondrial disease, coexisting adrenal insufficiency may be challenging to identify. A 36-year-old female presented for evaluation of fatigue, myalgia, and dyspnea for several years. She carried a diagnosis of asthma, myopathy, gastroparesis requiring a gastric stimulator, and recently diagnosed adrenal insufficiency secondary to long term fluticasone use. Beside low blood pressure of 91/64 millimetres of mercury, physical exam was unremarkable. Lab findings were significant for dehydroepiandrosterone-sulfate (DHEAS) of 7.0 micrograms per deciliter (mcg/dL), Adrenocorticotropic hormone (ACTH) of 7.2 picograms per milliliter and cortisol of 1.4 mcg/dL. Adrenal insufficiency was confirmed with cosyntropin stimulation test. Methacholine challenge test showed worsening asthma. She was managed with empiric stress dose steroids when indicated. Muscle fatigue progressed despite taking ubiquinol, B100 and carnitine. She was further evaluated with muscle biopsy that showed type two fiber atrophy. Muscle coenzyme Q10 was 0.08 mcg/dL, and citrate synthase was 50% of normal, insufficient for electron transport complex I. Whole exome sequencing showed mutations in NLRP1 in addition to Myosin Heavy Chain 2 (MYH2) and Sodium voltage-gated Channel alpha subunit 4 (SCN4a) both of which are associated with myopathy. She was then started on a short-acting glucocorticoid regimen. While her adrenal insufficiency was initially thought to be secondary to inhaled steroids, subsequent mutation analysis suggested that she was prone to autoimmunity. This case illustrates the association of adrenal insufficiency with NLRP1 mutation. Furthermore, the symptoms of adrenal insufficiency and myopathy can overlap making it difficult to delineate. While so far most studies have dealt with mitochondrial myopathies due to deletions or point mutations in the mitochondrial deoxyribonucleic acid (DNA), a new field of investigation is that of syndromes due to mutations in the nuclear DNA.