GIST (ILEAL) Revealed by Peculiar Paraneoplastic-myositis and Hypo-Thyroidism.

Introduction: To our knowledge this is the first & only case report in India wherein malignant ileal gastrointestinal-stromal-tumor presented with paraneoplastic-myositis & hypothyroidism.

Result: Herein August-2019 IPGMER-SSKM-kolkata 49-year-male laborer presented with 15-days acute onset gradually progressing symmetrical poly-arthralgia (bilateral shoulders & knee) and 10-days acute progressive symmetrical proximal myopathy along-with painfully swollen bilateral thighs and arms (restricted range of motion) besides fatigue for similar duration. absent characteristic skin changes. Neurological examination revealed power 4/5-upper-limbs & 3/5-lower-limbs) (preserved deep-tendon-reflexes all 4-limbs). Hb-13% AST-211 ALT-247 (negative-C3/C4) (negative-RF/antiCCP/ANA) (negative-Jo1 PL7 PL12 KU Mi2 Scl75) (CPK-1200, LDH-600 TSH-15.8) freeT4-1.8, CRP-2, ESR-80. NORMAL Thigh-muscle-electromyography and NORMAL muscle-biopsy. MRI-bilateral-Thigh revealed T2-hyper intensities within anterior-compartment thigh-muscles (bilaterally) (confirmed myositis). NORMAL contrast-CT-thorax. Contrast CT-abdomen confirmed exophytic 12 x 10 x 8 cm mass abutting ileal-loops). Following surgery (7-cm-mass completely resected from ileocecal-junction with negative-margin) (histopathology T4-N0-M0-stage-3B CD-117-positive DOG-1-positive ileal GIST pleomorphic-spindle-cell hyperchromatic-nuclei >5/50-hpf high mitotic-count. arthralgia-myopathy-swelling improved dramatically from 7th-day (post-surgery). TSH improved till 4.5 over next 2-months spontaneously (without ever-requiring supplementation). Patient was discharged on imatinib-400-mg single-daily-dosage. As of October 2022 on regular follow-up at AIIMS-Kalyani West Bengal (still in remission (continuing same dose).

Conclusion: Upto 10% dermato-myositis 5% poly-myositis can be paraneoplastic manifestation of underlying solid organ malignancy. overexpression of thyroid-hormone-inactivating type 3 iodothyronine deiodinase (D3) enzyme from GIST tumours often leads to hypothyroidism. References 1.Maynard MA, Marino-Enriquez A, Fletcher JA, et al. Thyroid hormone inactivation in gastrointestinal stromal tumors. N Engl J Med 2014;370:1327-1334. 2.Samimi M, Nseir A, Kerdraon R, et al. Tumeur stromale duodenale revelee par une dermatomyosite paranéoplasiqueStromal duodenal tumor revealed by paraneoplastic dermatomyositis. Gastroenterol Clin Biol 2008;32(12):1018-1020.