title: Isolated primary amyloidosis of the inferior rectus muscle mimicking Graves' orbitopathy.
abstract: The diagnosis of Graves' orbitopathy is usually straightforward. However, orbital diseases that mimick some clinical signs of Graves' orbitopathy may cause diagnostic confusion, particularly when associated to some form of thyroid dysfunction. This report describes the rare occurrence of localized inferior rectus muscle amyloidosis in a patient with autoimmune hypothyroidism, who was misdiagnosed as Graves' orbitopathy. A 48-year-old man complained of painless progressive proptosis on the left side and intermittent vertical diplopia for 6 months. The diagnosis of Graves' orbitopathy was entertained after magnetic resonance imaging revealing a markedly enlarged, tendon-sparing inferior rectus enlargement on the left side, and an autoimmune hypothyroidism was disclosed on systemic medical workup. After no clinical improvement with treatment, the patient was referred to an ophthalmologist and further investigation was performed. The presence of calcification in the inferior rectus muscle on computed tomography, associated with the clinical findings led to a diagnostic biopsy, which revealed amyloid deposition. This report emphasizes that a careful evaluation of atypical forms of Graves' orbitopathy may be crucial and should include, yet with rare occurrence, amyloidosis in its differential diagnosis. RESUMO O diagnóstico de orbitopatia de Graves usualmente é fácil de ser estabelecido. No entanto, doenças da órbita que simulam alguns sinais clínicos da orbitopatia de Graves podem levar à confusão diagnóstica, particularmente quando associada à alguma forma de disfunção tireoidiana. Relatamos a ocorrência rara de amiloidose localizada no músculo reto inferior em paciente com hipotireoidismo autoimune, que recebeu inicialmente o diagnóstico errôneo de orbitopatia de Graves. Paciente masculino, 48 anos, com queixa de proptose progressiva e indolor do lado esquerdo e diplopia vertical intermitente há 6 meses. O diagnóstico de orbitopatia de Graves foi considerado após a realização de ressonância magnética, que revelou aumento importante do músculo reto inferior esquerdo, sem acometimento do tendão, e uma propedêutica sistêmica detectou hipotireoidismo autoimune. Como não houve melhora com o tratamento clínico, o paciente foi encaminhado a um oftalmologista, que realizou nova investigação. A presença de calcificação no músculo reto inferior na tomografia computadorizada, associada aos achados clínicos, levou a uma biópsia da lesão, que demonstrou a deposição de material amiloide. Este relato enfatiza como uma avaliação minuciosa das formas atípicas de orbitopatia de Graves é essencial e deve incluir a ocorrência, embora rara, de amiloidose no diagnóstico diferencial da orbitopatia de Graves.
authors.affiliation: Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Mário Luiz Ribeiro
authors.initials: ML
authors.lastname: Monteiro
authors.affiliation: Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Allan Christian Pieroni
authors.initials: AC
authors.lastname: Gonçalves
authors.affiliation: Hospital Israelita Albert Einstein, São Paulo, SP, Brazil.
authors.forename: Alanna Mara Pinheiro Sobreira
authors.initials: AM
authors.lastname: Bezerra
mesh_terms: D000686:Amyloidosis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D001706:Biopsy; D005141:Eyelid Diseases / Q000000981:diagnostic imaging; D049970:Graves Ophthalmopathy / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000473:pathology; D050031:Hashimoto Disease / Q000175:diagnosis; D006801:Humans; D000075363:Immunoglobulin Light-chain Amyloidosis; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000000981:diagnostic imaging / Q000473:pathology; D013967:Thyroiditis, Autoimmune / Q000175:diagnosis; D014057:Tomography, X-Ray Computed