Hypothyroidism masquerading as polymyositis

A Complex Case of Polymyositis Overlapping With Hypothyroid Myopathy Without Underlying Autoimmune Thyroid Disorder

A 78-year-old woman with a past medical history of hypothyroidism and Sjogren's syndrome presented with a two-month history of gradually progressive bilateral lower extremity weakness. Significant elevation in thyroid-stimulating hormone (TSH) and muscle enzyme, such as creatine kinase, was noticed on presentation. Due to concerns of hypothyroid myopathy, the patient was started on thyroxine and triiodothyronine supplementation. The patient reported no significant improvement in her weakness in the one-month follow-up. Laboratory workup revealed improving TSH levels but worsening creatine kinase levels. Electromyography study showed primarily myopathic features, such as abnormal insertional activity concerning for mild inflammatory myopathy. Muscle biopsy showed mild inflammatory exudate and features of myopathy with ongoing denervation. The patient was diagnosed with polymyositis and started on prednisone 0.5 mg/kg daily with a taper course and methotrexate. The patient reported significant improvement in her weakness when seen in six weeks with normalizing creatine kinase levels. The hallmark difference between hypothyroid myopathy (including polymyositis-like syndrome) and conventional polymyositis is the complete clinical recovery and resolution of laboratory abnormalities after treatment with thyroid hormone replacement in hypothyroid myopathy. There was no evidence of underlying autoimmune thyroid disorder which makes this case unique. This case highlights the complex case of polymyositis overlapping with hypothyroid myopathy with no underlying autoimmune disorder.

Rhabdomyolysis and peroneal nerve compression associated with thyroid hormone withdrawal in the setting of remnant ablation: review of the literature

OBJECTIVE

To review the putative mechanisms whereby hypothyroidism is associated with severe myopathy, neural injury, and acute compartment syndrome and report a case of nontraumatic common peroneal nerve compression associated with hypothyroidism-induced rhabdomyolysis in a patient with diabetes prepared for remnant ablation after thyroidectomy for differentiated thyroid carcinoma.

METHODS

We performed a review of the English-language literature on the PubMed database using the terms hypothyroidism, muscle disease, hypothyroid myopathy, rhabdomyolysis, compression neuropathy, and acute compartment syndrome.

RESULTS

Myopathy occurs frequently among patients with overt hypothyroidism; however, severe myoneural injury seems to be precipitated or accompanied by comorbid conditions. Focal peroneal neuropathy may be related to hypothyroidism-induced extrinsic compression from severe myopathy and soft tissue swelling in a narrowed fascial compartment.

CONCLUSION

Severe short-term iatrogenic hypothyroidism may lead to severe myopathy and compression nerve injury in patients with underlying diabetic neuropathy. We recommend avoidance of withdrawal of thyroid hormone for purposes of remnant ablation among patients with preexisting diabetic neuropathy.

Clinical significance of thyroid disease in patients with inflammatory myopathy

We conducted the current study to determine the prevalence, incidence density, and clinical significance of thyroid disease in a series of 109 patients diagnosed with idiopathic inflammatory myopathy. We analyzed 109 patients diagnosed with idiopathic inflammatory myopathy during a 20-year period (1986-2006). Routine determination of thyroid profile, including hormone levels and antithyroid antibodies (antithyroid peroxidase and antithyroglobulin antibody systematically, and antithyroid-stimulating hormone receptor antibody when appropriate) was carried out at onset and at least once again during the follow-up period. Human leukocyte antigen (HLA) study was performed by polymerase chain reaction sequence-specific oligonucleotide typing. Six patients (5.5%) developed thyroid disease (hypo- or hyperthyroidism), with an incidence density of 8.7 new cases per 1000 person-years; 4 of the 6 cases were of autoimmune origin (3.6%). Thyroid dysfunction, whether autoimmune or not, was clearly related with onset or relapse of disease activity. Neoplastic disease was detected in 3 of 4 (75%) patients with autoimmune thyroid disease, a significantly higher frequency than was observed in the remaining patients in the series (12 of 103, 11.7%; p < 0.05; RR: 22.8; 95% confidence interval, 2.2-236.6). HLA DRB1*04 was found in 4 of the 6 patients with thyroid disease and inflammatory myopathy. Thyroid disorders are clinically relevant in patients with inflammatory myopathies. An association was observed between autoimmune thyroid disease and cancer. Thyroid assessment is strongly recommended in patients with idiopathic inflammatory myopathy and clinical relapse.

Polymyositis-like syndrome in hypothyroidism: review of cases reported over the past twenty-five years

Polymyositis-like syndrome, with proximal muscle weakness and elevation of muscle enzymes, may be a clinical manifestation of hypothyroidism. To define the clinical, biochemical, electromyographic, and pathologic characteristics of patients with this syndrome, we identified and reviewed by MEDLINE all cases reported in the English literature from January 1, 1975 through December 31, 2000. Thirty-two cases were considered. Fifty-nine percent of the patients were male with a mean age of 54.7 +/- 22.6 years, (+/- 1 standard deviation [SD]). Weakness was described in 100% of patients. Other common clinical manifestations were: delayed tendon reflexes with slow relaxation phase (41%), muscle tenderness (25%), and muscle induration (9%). The mean creatine kinase (CK) was 2164 +/- 1954 U/L (+/- 1 SD) and the mean thyroid-stimulating hormone (TSH) was 114.8 +/- 85.6 mIU/L (+/- 1 SD). Fifty percent of patients had electromyography; half of the studies were normal while the other half showed nonspecific myopathic changes. Biopsies were performed in 80% of the patients. The most common findings were type II fiber atrophy, type I fiber hypertrophy, central nuclei disposition, necrosis, increased percentage of type I fibers, and decreased percentage of type II fibers, inflammatory infiltrate and the presence of core-like structures. The characteristics of polymyositis-like syndrome in hypothyroidism did not differ from those of nonspecific hypothyroid myopathy. Clinical judgment alone may not be sufficient to suspect and detect these patients. Serum TSH levels should be routinely determined in all patients with muscle weakness or elevation of creatine kinase.

Hypothyroidism presenting as destructive arthropathy of the fingers

A patient presenting with destructive arthropathy of the proximal interphalangeal (PIP) joints of the hands is described. She was initially believed to have rheumatoid arthritis but non-steroidal anti-inflammatory drugs were of no help. The patient was subsequently found to have hypothyroidism and erosive osteoarthritis of the fingers. Joint swelling, pain and stiffness responded dramatically to thyroid hormone substitution. The PIP joint spaces reappeared on the radiographs within 9 months. This case suggest that hypothyroidism may induce destructive arthropathy of the finger joints. As thyroxine replacement may reverse the rheumatic complaints, hypothyroidism should be considered in the differential diagnosis of a destructive arthropathy of unclear aetiology.

Hypopituitarism associated with myalgia

A patient with panhypopituitarism who presented with muscle pain and stiffness is described. These symptoms responded rapidly to treatment with thyroxine and cortisone acetate. The association between muscle disease and hypopituitarism is briefly reviewed.