Histopathological Evidence of Thyroid Dermopathy and its Correlation with Thyroid-Associated Orbitopathy in Patients with Graves’ Disease having Normally Appearing Pretibial Skin: A Case-Control Study

OBJECTIVE: Thyroid dermopathy (TD), reportedly encountered in less than 5% of patients with Graves’ disease (GD), is supposed to coexist only with thyroid-associated orbitopathy (TAO). However, clinically inapparent TD, detected non-invasively by thermal imaging or ultrasonography, seems to be present in a larger proportion of GD. Histopathological examination (HPE), though considered as gold standard for detecting TD, has not been performed widely to identify subclinical TD in GD. MATERIALS AND METHODS: In this single-centre, cross-sectional, case-control study, 50 patients with GD (cases) and normal appearing pretibial skin were compared with 45 age- and sex-matched individuals (39 healthy volunteers, 3 with toxic multinodular goitre and 3 with solitary toxic nodule) (control). All patients were evaluated clinically for presence of TAO. Punch biopsy specimens were obtained from the pretibial skin in all 95 participants. Tissue sections were examined under light microscopy for mucin deposition, splitting of collagen fibrils and perivascular lymphocytic infiltration. RESULTS: Sixty per cent of patients with GD demonstrated at least one of the above three histological features, while 52% had any combination of two features and 46% harboured all the three features. Mucin deposition, splitting of collagen fibrils and lymphocytic infiltration were found overall in 52%, 54% and 52% of GD, respectively; 4.4–11.1% of controls also had some evidence of TD on HPE. Subclinical TD was not related to age, duration of disease and TAO in our study. CONCLUSIONS: TD, particularly in its subclinical form, Seems to be widely prevalent in GD (46–60%) and exists even in absence of TAO. HPE, though more sensitive than the various non-invasive tests, is not specific (ranges from 89% to 95%) for TD. However, HPE can accurately diagnose TD in appropriate clinical background.