014040 Gao Jianxin Li Junying, Department of Rheumatology and Immunology, Baotou Central Hospital, Inner Mongolia, China Abstract Objective To investigate the diagnosis and treatment of patients with polymyositis-like syndrome (PLS) caused by hypothyroidism. Methods To investigate thyroid function, muscle enzyme profile, anti-nuclear antibody (ANA), anti-Jo-1 antibody, electromyography and muscle biopsy if necessary, to find out whether hypothyroidism exists, except polymyositis and dermatomyositis, in patients with muscle pain, muscle weakness with edema. Patients with definite hypothyroidism were given levothyroxine or thyroid tablets, and hydrocortisone was given as appropriate for mucous edema. Results Hypothyroidism can lead to polymyositis-like manifestations, with decreases in triiodothyronine (T3) and thyroxine (T4), decreases in free T3 and T4, elevations in thyroid-stimulating hormone (TSH), and elevations in myoenzyme profiles. Most of them can recover to normal range after treatment, and continue to be treated with maintenance dose and regular review. Conclusion This disease is very easy to be misdiagnosed in the early stage and needs more attention. The following is a typical case to discuss the diagnosis and treatment of these patients. Gao Jianxin, Department of Immunology, Baotou Central Hospital, Baotou, China. The patient was a 52-year-old male with generalized edema and muscle pain in the limbs. He had been checked in the local hospital for blood and urine routine and liver and kidney functions, and was not treated with traditional Chinese medicine for kidney deficiency. She had no thyroid disorders and no history of pituitary or thyroid surgery. Physical examination: body temperature 36.1℃, pulse 82 beats/min, respiration 19 beats/min, blood pressure 100/60mmHg, face with mucoid edema, indifferent expression, no yellowish staining of the skin, dry skin, poor elasticity. There were no abnormalities in the heart, lungs, or abdomen, and a DR chest radiograph showed enhanced lung texture. Free T30.01pg/ml (reference value 1.45~3.48), free T40.01ng/dl (reference value 0.71~1.85), TSH162.808µIU/ml (reference value 0.490~4.670), blood and urine routine were generally normal, myoenzyme profile was characterized by increased CK, Jo-1 and ANA were not abnormal. Preliminary diagnosis of hypothyroidism with PLS was made, and the patient was given daily morning oral levothyroxine tablets (Euthyrox) 50µg, and temporary hydrocortisone succinate 100mg. His condition improved day by day, and after one month, there was no obvious edema in the face and the whole body, chest X-ray was not abnormal, and cardiac and abdominal ultrasound did not show any abnormality. FT32.55µg/ml, FT40.86ng/dl, TSH2.556µIU/ml, all three were restored to the normal range, muscle enzyme spectrum was normal, and thyroid tablets were given to maintain the treatment, and then said that there was a cramp in the calves, and the blood calcium was 2.0mmol/L, phosphorus was 1.06mmol/L, and magnesium was 0.70mmol/L, and no special discomfort was observed after calcium and magnesium supplementation. After calcium and magnesium supplementation, there was no further special discomfort. Discussion[1][2][3] Hypothyroidism is a group of endocrine diseases caused by a variety of causes of thyroid hormone synthesis, secretion or biological effects of insufficient, clinically about one-third of the patients with hypothyroidism have musculoskeletal symptoms, most of the symptoms are mild and non-specific, only a small number of patients with hypothyroidism appeared to the shoulder girdle, pelvic girdle, proximal limb muscle weakness accompanied by a significant elevation of muscle enzymes, with oedema, that is, the PLS, first described by Ord in 1880, typically may present with muscle soreness, weakness, painful muscle spasms, myotonic-like changes, markedly elevated CK, and lack of muscle atrophy, and is more common in males than in females, has an age of onset similar to the average age of onset of hypothyroidism (40-60 years old), and needs to be compared with polymyositis/dermatomyositis, hereditary myopathies, and rhabdomyolysis, motor neuron disease, acute coronary syndrome (ACS), myocarditis, etc. It also needs to be differentiated from hypothyroidism arthropathy. Hypothyroidism causes CK to be elevated in some cases up to 100 times or more, and CK-MB is not significantly elevated, whereas CK and CK-MB are both high in patients with ACS, but CK-MB is the most prominent, and some troponin is significantly elevated, and cardiac enzymes are all elevated to varying degrees. The mechanism of increased myosin may be related to the following factors [1]:1 Mucopolysaccharides and mucins are deposited in all muscle tissues throughout the body, and interstitial edema of myocytes, swelling and degeneration or even fracture and necrosis of muscle fibers can occur, resulting in myosin overflowing from the cell, and it is the main cause of the increase of various myosin enzymes, mainly CK, and it is the most obvious in transverse muscle involvement.2 T3 can stimulate the partial clearance of CK, and in hypothyroidism In hypothyroidism, T3 decreases and CK clearance decreases, resulting in increased serum CK.3 In hypothyroidism, CK activity factor increases myocardial membrane permeability, and ATP deficiency and hypothermia in hypothyroidism can lead to increased release of CK from muscle. Electromyography shows that the probability of myogenic damage is significantly lower than that of polymyositis, and it has been reported that PLS caused by hypothyroidism shows type 2 muscle fiber atrophy, which is one of the differences from polymyositis. In addition, PLS caused by hypothyroidism may be accompanied by hypertrophy and necrosis of type 1 muscle fibers, infiltration of inflammatory cells, and occasionally glycogen vacuoles in severe cases. Ultrastructural changes are seen as non-specific myofilament degeneration, Z-line hydrophobia, lipofuscin accumulation, and mild mitochondrial degeneration. The most important basis for differentiating polymyositis from PLS due to hypothyroidism is that the latter will have a faster decrease in CK to normal with thyroid hormone replacement therapy, with gradual recovery of muscle weakness, and some immunologic markers, such as antinuclear antibodies, anti-ENA antibodies, and anti-Jo-1 antibodies, are negative. Only nearly a quarter of patients have myogenic damage on electromyography. In the former case, adrenocorticotropic hormone therapy was required, and in some patients, immunosuppressive drugs were added, and the recovery of muscle strength and the decrease of CK were slow after treatment. In conclusion, the main points of diagnosis of PLS caused by hypothyroidism are: 1. meet the diagnostic criteria of hypothyroidism; 2. have the manifestation of myasthenia gravis and CK increase; 3. myasthenia gravis symptom is relieved after thyroxine replacement therapy, and CK returns to normal. Endocrinologists and rheumatologists should be alert to the possibility of hypothyroidism causing polymyositis-like syndrome in patients with muscle pain, muscle weakness with edema, and perform necessary thyroid function screening and cardiac enzymes to avoid misdiagnosis and mis-treatment; and if necessary, check electromyography and muscle biopsy to distinguish PLS caused by hypothyroidism from polymyositis, which is well treated by supplemental thyroid hormone therapy, with marked improvement of myositis-like symptoms and muscle enzymes, and helps to distinguish it from polymyositis. In the former, thyroid hormone supplementation is effective, and myositis-like symptoms and muscle enzymes are significantly improved, which helps to differentiate from polymyositis. It is worth noting that when the former supplemented thyroid hormone replacement therapy, attention should be paid to follow-up, timely review of thyroid function, and adjustment of the dose of medication to avoid the occurrence of pharmacological hyperthyroidism. References 1. Deer B, Du YP, Hu RM, et al. Four cases of primary hypothyroidism causing polymyositis-like syndrome and literature review. Chinese Journal of Rheumatology, 2008, 12: 819-821. 2. Dai, M., Zheng, D. F., Mo, Y. Q.. Three cases of hypothyroidism with polymyositis-like syndrome. Chinese Journal of Internal Medicine, 2007, 46: 244.3. Li Jian. Multiple myositis-like syndrome. Shan Yundong, Zeng Xuejun, Huang Xiaoming, Liu Xiaohong, eds. Diagnosis of Difficult Diseases in Internal Medicine: Examples of Clinical Thinking of Concordia Physicians. Beijing: Peking Union Medical College Press. 2007.5 First Edition. 381-383.