Thanks Eliot for presenting a great case. This is a case of an elderly gentleman with a history of fibromyalgia, exogenous iodine intake presenting with subacute progressive lower extremity weakness found to have abnormal TFTs and troponemia found to have a biopsy proven idiopathic inflammatory myopathy.
- 1) The approach to weakness can be thought of as CNS, PNS, oxygen delivery and psych. See this blog post for more information.
- 2) Patients with a new diagnosis of dermatomyositis and polymyositis should have had age appropriate cancer screening.
- 3) Iodine is found in many foods including seaweed, kelp, certain medications (eg amiodarone) and in contrast agent. A person with a normal thyroid should be able to regulate excess exogenous iodine intake but someone with hypothyroidism may develop clinical hyperthyroidism.
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- There are 4 main types of inflammatory myopathies, DM, PM, IBM and necrotizing autoimmune myositis.
- Key features pre-biopsy/ testing of each include:
- DM – characteristic skin rash
- PM – usually diagnosis of exclusion
- IBM – distal muscle weakness with atrophy of hand muscles
- NAM – very high CK levels
- Treatment of dermatomyositis and polymyositis generally consists of steroids. Refractory disease may benefit from rituximab and IVIG.
Here is a great chart from an NEJM review article on inflammatory muscle disorders.
- the differential for a high TSH and normal fT4/T3 includes subclinical hypothyroidism, drugs and euthyroid sick syndrome
- check T3 if someone has clinical hyperthyroidism but normal TSH/T4
Here is an excellent video by Palo Alto VA Internist/ clinician educator Eric Strong on interpretation of abnormal thyroid function tests.