[Muscle weakness and CK elevation: is it myositis?] / Muskelschwäche und CK­Erhöhung: Ist es immer eine Myositis?

Rheumatologists are often confronted by patients with muscle weakness and elevated creatine kinase (CK) levels. Myositis cannot always be determined to be the cause of the complaints. This article presents two cases from our hospital where the diagnosis could only be determined by muscle biopsy. In the first case the patient presented with muscle weakness, pathological weight loss and a significant increase in CK levels. A muscle biopsy revealed an immune-mediated necrotizing myopathy (IMNM) caused by anti-3-hydroxy-3-methyl-gulatryl-CoA reductase (HMG-CoA reductase) autoantibodies due to the intake of statins. The second patient presented with cramp-like and burning muscle pain and weakness of the extremities without a relevant increase in CK level. Myoadenylate deaminase deficiency was also detected by muscle biopsy, and further confirmed by genetic testing.

Lowest effective 131I activity for thyroid remnant ablation of differentiated thyroid cancer patients. Dosimetry-based model for estimation.

AIM: A theoretical dosimetry-based model was applied to estimate the lowest effective radioiodine activity for thyroid remnant ablation of low-risk differentiated thyroid cancer patients. PATIENTS, METHODS: The model is based on the distribution of the absorbed (radiation) dose per administered radioiodine activity and the absorbed dose threshold of 300 Gy for thyroid remnants, the level believed to destroy most thyroid remnants. For this purpose, ¹²4I PET/CT images of 49 thyroidectomised patients were retrospectively analysed to measure the distribution of the (average) absorbed doses to thyroid remnant per administered ¹³¹I activity. The fraction of thyroid remnants that received at least 300 Gy was determined for standard activities between 0.37 and 5.55 GBq. The lower activity was considered to be equally effective to that obtained with higher activity if the (absolute) fraction difference was below 5%. RESULTS: A total of 62 thyroid remnants were included. The medians and ranges (in parentheses) for the absorbed dose per unit 131I activity were 359 Gy/GBq (34 to 1825 Gy/GBq). The fractions of thyroid remnants receiving more than 300 Gy at different therapy activities (within parentheses) were 60% (1.11 GBq), 76% (1.85 GBq), 79% (2.22 GBq), and 81-82% for activities between 2.59 and 3.70 GBq. The therapy activity of 1.11 GBq is considerably less effective than that of 1.85 or 2.22 GBq; therapy activities were equally effective in the range between 2.22 to 3.70 GBq. CONCLUSION: On the basis of the model and the patients' data included, the lowest effective therapy activity appears to be approximately 2.2 GBq to ablate thyroid remnants. The results of this study may help to guide the design of prospective clinical studies.