Introduction Amyloidosis is a collective term used for a group of uncommon metabolic disorders, wherein insoluble amyloid protein-fibres are deposited in the tissues and organs. Mucocutaneous manifestations are observed in both the non systemic and systemic types of amyloidosis.
Extrathyroidal manifestation of Graves’ disease are well known presenting as pretibial myxedema. Other manifestations include hyperpigmentation, and possible nail abnormalities.
Clinical case A 15 year old Asian girl diagnosed as Graves’ Disease in December 2005 who was treated with Carbimazole and then with radioactive iodine on two occasions, reported to the out patients for follow up. Clinically she was euthyroid and had been in remission and not requiring any medication (Figure 1).
She was observed to have painless, dry and non pruritic unexplained hyperpigmentation of her skin on her arms and back. There were no signs of inflammation or infection with no involvement of nail or mucosa. She had an initial work up which included thyroid function test, coagulation screen, Von willibrands factors, ANA and short synactin test which were all normal. Eventually she had a skin biopsy which revealed evidence of interface dermatitis with post inflammatory pigmentation possibly primary cutaneous amyloidosis (Figure 2).
Discussion Primary localised cutaneous amyloidosis is, by definition, amyloid deposition limited to the skin and not associated with underlying systemic illness.
Three variants described are, lichen, macular and nodular amyloidosis. In the former two, the deposited amyloid is keratinocyte derived. In the rare form of nodular amyloid it is derived from local plasma cells.
Lichen amyloidosis occurs primarily on the shins, although other mainly acral sites may be involved. It is thought to be more common in the Asian population.
Amyloid globules are visualised under polarised light microscopy with Congo red stain assuming apple-green birefringence. On electron microscopy amyloid appears as haphazard and wavy 6–10 nm non-branching filaments.
Cutaneous amyloidosis in association with endocrinal disorders has been reported to occur in multiple endocrine neoplasia type 2A.
Conclusion In conclusion, this is the first reported association of Primary cutaneous amyloidosis (PCA) with Graves’ disease. As both diseases have commonalities, the causal pathway of chronic inflammation may be the reason for the association, meanwhile radioiodine has never been associated with PCA.
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