Endocrine Abstracts

Case History: A 60 year-old male presented to ED with an elevated Creatinine Kinase (CK) of 16,685IU/l (40-320), ALT 788 IU/l (9-59), AST 785 IU/l (11-34) and lower limb fatigue and weakness. There was no upper limb or skin involvement. He had a ST-Elevation Myocardial Infarction in 2022, Coeliac Disease, and Trigger Finger. Statin therapy was stopped, and IV fluids commenced. CK down trended to 11,000IU/l in 24 hours. He was discharged with urgent rheumatology follow-up. 10days later, he presented with progressive weakness and difficulty swallowing food. He was admitted for further work-up.

Investigations: MRI thigh showed extensive symmetrical pelvic and thigh myositis bilaterally. Muscle biopsy revealed myonecrosis of the thigh. EMG studies exhibited fibrillations, percussion myotonia and polyphasic compound motor units. Ultrasound liver and standard autoimmune panel were normal. OGD showed no evidence of oesophageal pathology. CT-TAP for paraneoplastic work up showed a left 26 Hounsfield units, 3.1cm enhancing adrenal mass. Adrenal functional work-up revealed plasma normetanephrines of 3990 pmol/l (<1050) and plasma metanephrine of 1160 pmol/l (<360). Pituitary profile and 24 hr urinary free cortisol collection were normal. Extended Myositis panel was positive for Anti-HMGCoA Reductase antibody 363CU (<20).

Results and Treatment: Methylprednisolone, mycophenolate and IVIG were commenced followed by maintenance prednisolone for treatment of immune mediated necrotising myopathy. He was alpha blocked with doxazosin and then phenoxybenzamine prior to adrenalectomy. Steroid regimen was successfully weaned.

Conclusion and Points for Discussion: This case highlights the (i) importance of cross-speciality input and (ii) two rare potential causes of myopathy. (i) Multi-speciality input allowed us to arrive at two rare diagnoses and for adequate surgical preparation pre-op. (ii) Immune-mediated necrotising myopathy and pheochromocytoma are rare potential causes of myopathy. Given the lack of other symptoms usually present with pheochromocytoma, it’s more likely that this was an incidental finding.