A Rare Case of Anti-NXP2 Antibody Positivity in Juvenile Dermatomyositis – A Case Study

dc.creatorBosques, Rebecaen_US
dc.creatorQuresh, Quretulen_US
dc.description.abstractBackground: Dermatomyositis (DM) is one of the many subcategories of Idiopathic Inflammatory Myositis (IIM), a treatable group of myopathies. Antibodies serve as a diagnostic tool with prognostic indicators. DM-specific antibodies include anti-NXP2, anti-MDA5, anti-TIF1gamma, Anti-Mi2, Anti- SAE, and anti-SRP. These DM-specific antibodies are mutually exclusive suggesting the idea that each plays a specific role in shaping different phenotypes. 1-17% of adult DM/ polymyositis (PM) and 23-25% of juvenile dermatomyositis (JDM) present with a positive anti-NXP2 antibody. Clinically, positive anti-NXP2 antibody DM patients present with a rash, debilitating muscle weakness, calcinosis, dysphagia, and a higher risk of malignancy. As compared to patients with negative anti-NXP2 antibody DM, positive anti-NXP2 antibody DM patients were younger at the age of onset, with shorter duration between symptom onset to diagnosis, and no significant sex diseases. The prognosis for positive anti-NXP2 antibody DM depends on the complications developed. The worrisome complications which lead to a poor prognosis are calcinosis and malignancies. Case Information: 22 y/o female was referred to rheumatology for evaluation of Systemic Lupus Erythematosus (SLE). For 3 years prior, the patient experienced muscle and generalized weakness, and myalgia in the legs leading to difficulty climbing stairs. At the time of referral, the patient showed CPK 34, ANA positive anti-dsDNA +12, BUN 15, creatinine 0.70, GFR 123, albumin 4.6, AST 15, ALT 6, ESR 35, WBC 6.5, hemoglobin 10.8, platelets 320. On physical exam, upper and lower extremities showed 4/5 muscle strength. An autoimmune panel to test myositis specific antibodies was ordered. Which showed positive anti-NXP2 21, positive ANA screen IFA, actin antibody (IgG) 34, thyroid peroxidase antibodies 267 IU/mL, ANA titer 1:80. 20 days after, the patient had difficulty getting out of bed with profound generalized weakness. The patient had developed a rash in the upper chest and abdomen. The diagnosis of juvenile dermatomyositis (JDM) was made. Patient admitted to hospital treated with 1 g Methylprednisolone for 3 days and tapered 1 mg/kg body weight. Care with neurology was coordinated to start IVIG treatment at 2 g/kg body weight. The patient was found to have positive acetylcholine receptor antibodies and diagnosed with Myasthenia gravis. The patient was given IVIG for 5 days. The patient was also found to have thyroid nodule swelling s/p biopsy concerning Hurthel cell cancer. On follow-up one month later, the patient stated a return of muscle strength with no rashes. The patient was advised to get an EMG and follow up with neurology, the dose of prednisone was decreased to 40 mg daily and advised to take vitamin D 50,000 units weekly. Conclusion: Anti-NXP2 antibody positive JDM has a poor prognosis compared to other subcategories. This stems from increased risk of malignancies and calcinosis leading to fatalities. Our patient was a rare case with anti-NXP2 antibody positive JDM, Myasthenia gravis, and Hurthle cell cancer. There is an increased need in data and research regarding NXP2 antibody and its heterogenous prognosis with DM patients.en_US
dc.titleA Rare Case of Anti-NXP2 Antibody Positivity in Juvenile Dermatomyositis – A Case Studyen_US