Graves' autoantibodies to extrathyroidal TSH receptor: their role in ophthalmopathy and pretibial myxedema.
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In the present study we have evaluated the use of pretibial ultrasound for the diagnosis of pretibial myxedema (PTM). We studied 76 patients, 58 with Graves' disease, 13 with Hashimoto's thyroiditis and five with idiopathic hypothyroidism. Thirty-two normal subjects were also studied as controls. Sixty-four patients had associated ophthalmopathy. The ultrasound scanner was equipped with 10- and 13-MHz probes. Punch biopsies were carried out in 11 patients and tissue sections examined on a light microscope. On clinical examination 21 patients (28%) had suspected PTM. By ultrasound, we measured the thickness of dermis and subcutaneous tissue (D1) and that including only deeper dermis (D2) in normal subjects to define the echographic parameters of normal pretibial skin. We then found increased skin thickness in 25 patients (33%), with mean D1 and D2 values significantly higher than those measured in controls (p < 0.00001). The echographic study was positive in 20 patients with ophthalmopathy (31%). Ultrasound showed increased skin thickness in 16 of 21 patients (76%) with clinically suspected PTM. Histopathological findings confirmed the presence of PTM in all the patients who underwent pretibial skin biopsy. We believe that the measurement of pretibial skin thickness by ultrasound may be useful for revealing the presence of PTM.
We describe a patient with monoclonal gammopathy who subsequently developed thyrotoxicosis, pretibial myxedema and thyroid-associated ophthalmopathy. The pathogenesis of thyrotoxicosis in Graves' disease is due to the presence of autoantibodies that mimic the action of thyrotropin (TSH), called thyroid-stimulating antibodies (TS-ab); these antibodies may or may not inhibit the binding of TSH to the receptor (thyroid-binding inhibiting immunoglobulin, TBII). The patient's immunoglobulins were TS-ab positive and TBII negative when measured on CHO cells expressing the human TSH receptor. The pathogenetic link between the thyroid, orbit and skin is yet to be established but several candidate shared antigens have been proposed, including the TSH receptor itself. The monoclonal immunoglobulins were in evidence before the symptoms of pretibial myxedema, thyrotoxicosis and ophthalmopathy. In addition, the patient had no autoantibodies to thyroglobulin or thyroperoxidase, which are classic markers of thyroid autoimmunity. This combination led us to postulate that the monoclonal gammopathy could be the cause of all the observed pathology. One method to test this hypothesis would be to show that the monoclonal immunoglobulin is a TS-ab. Various methods were used to separate the monoclonal from the polyclonal components of the patient's serum. Preparative isoelectric focusing enabled us to obtain fractions containing only the monoclonal (as revealed by polyacrylamide gel electrophoresis), which were devoid of TS-ab activity (measured as cAMP accumulation in CHO cells expressing the human TSH receptor in a hypotonic bioassay). Subsequently, different oligoclonal fractions were shown to have varying degrees of TS-ab activity, with one fraction having faint biological activity and able to recognize a recombinant TSH receptor preparation in a Western blot. In conclusion, the monoclonal antibody does not seem to be responsible for the thyrotoxicosis, pretibial myxedema and ophthalmopathy. We confirm previous data showing that TSH receptor antibodies in patients with Graves' disease are heterogeneous in nature and we present the first demonstration of autoantibodies capable of binding the TSH receptor but devoid of TBII activity.
Pretibial myxedema (PTM), mainly characterized by the accumulation of glycosaminoglycans in the dermis and subcutaneous tissue, is an extrathyroidal manifestation of autoimmune Graves' disease (GD), almost always associated with Graves' ophthalmopathy (GO). The thyrotropin receptor (TSH-R) has been proposed as the common target antigen in GD, GO and PTM, with evidence for receptor transcripts and/or protein in these locations. The aim of this study has been to investigate whether receptor protein is present in the pretibial tissues. Skin biopsies were obtained from two patients with PTM and two normal subjects without thyroid disease. A portion of each sample was fixed to produce semi-thin sections for Toluidine Blue or Periodic Acid Schiff (PAS) staining. The remainder was snap frozen to generate cryostat sections for immunohistochemical analysis using three monoclonal antibodies against TSH-R. In the skin from the two patients suffering from PTM, the dermis was infiltrated by inflammatory cells (lymphocytes, B cells, macrophages, mast cells) and adipocytes. The collagen fibers were dissociated by edema and by the accumulation of a PAS-positive material. Immunodetection of TSH-R produced positive staining on cells localized in the dermis, beneath the epidermis or close to the hypodermis. These cells were elongated and resembled fibroblasts. No immunoreactivity was observed in the dermis from control patients without thyroid disease. In conclusion, we have evidence for TSH-R immunoreactivity in the pretibium of patients with GD, GO and PTM. Further studies are needed to unambiguously identify the positive cells and determine whether the reactivity is due to the receptor itself or to a cross-reacting protein.
We report the case of a one-day-old newborn infant, female, birth weight 1900 g, gestational age 36 weeks presenting with necrotizing fasciitis caused by E. coli and Morganella morganii. The newborn was allowed to fall into the toilet bowl during a domestic delivery. The initial lesion was observed at 24 hours of life on the left leg at the site of the venipuncture for the administration of hypertonic glucose solution. Despite early treatment, a rapid progression occurred resulting in a fatal outcome. We call attention to the risk presented by this serious complication in newborns with a contaminated delivery, and highlight the site of the lesion and causal agents.
Pretibial myxedema or localized myxedema or thyroid dermopathy is an autoimmune manifestation of Graves' disease. It also occasionally occurs in Hashimoto's thyroiditis. Lesions of thyroid dermopathy are usually asymptomatic and have only cosmetic importance. Advanced forms of dermopathy are associated with elephantiasis or thyroid acropachy. Almost all cases of thyroid dermopathy are associated with relatively severe ophthalmopathy. Usually ophthalmopathy appears first and dermopathy much later. All patients with localized myxedema have high serum concentrations of thyroid-stimulating hormone receptor antibodies, indicating the severity of the autoimmune condition. Occurrence of thyroid dermopathy in areas other than pretibial skin indicates a systemic process. Similar to Graves' ophthalmopathy, thyroid-stimulating hormone receptors in the connective tissue may be the antigen responsible for the immune process. Both humoral and cellular immune mechanisms are involved in the stimulation of fibroblasts and the production of large amounts of glycosaminoglycans. Localization in the pretibial area relates to mechanical factors and dependent position. Diagnosis of thyroid dermopathy is based on signs and typical pretibial skin lesions in association with a history of Graves' hyperthyroidism and ophthalmopathy. In some cases, skin biopsy is needed for confirmation. The lesions are usually mild and are overshadowed by more symptomatic ophthalmopathy. Most cases of thyroid dermopathy do not require any therapy. In mildly severe symptomatic cases and when there is cosmetic concern, topical corticosteroids applied under occlusive dressing are beneficial. In more severe cases, systemic immunomodulation may be necessary; however, conclusive evidence for long-term efficacy of these modalities is lacking. When significant edema and elephantiasis are present, local compressive therapy may have added benefit. In mild cases that do not require treatment, 50% of patients achieve complete remission after several years. Severe cases that receive topical corticosteroids or other therapies do not have a better outcome than untreated milder cases. Current treatment modalities for thyroid dermopathy and acropachy are at best palliative. Better and safer means of immunomodulation are needed.
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A patient with porokeratosis Mibelli is reported who suffered from long-standing chronic active hepatitis and rapidly expanding vitiligo of more recent onset. This type of disease association has never been reported before, although it is in line with several reports of porokeratosis in association with immunoregulatory disorders, mostly after drug-induced immunosuppression. The lesions of the present patient responded well to treatment with topical 5-fluorouracil.
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Stasis dermatitis is an itchy, scaly, and hyperpigmented condition of the lower leg due to venous insufficiency. Hemosiderin and/or melanin have been considered responsible for the brown pigmentation. However, there are not sufficient histopathologic studies. In this retrospective study the hospital records and biopsy slides of 20 patients were reviewed to determine the pathogenetic mechanisms of brown pigmentation in stasis dermatitis. Fifteen were men (75%) and 5 were women (25%) with a mean age of 46.2+/-8.2 yr (18-76), mean age at onset of 43.4+/-18.0 yr (17-73), and a mean duration of the disease 2.8+/-2.5 yr (0.25-10). All patients had varicose vein and complained of pruritus. On histopathologic evaluation, two cases out of 20 (3 skin biopsy specimens from 25 samples) showed dermal melanocytes containing melanin, and incontinence of melanin pigment was observed in 5 cases, which indicates that melanin pigments from epidermis could contribute to cutaneous pigmentation in stasis dermatitis. However, the existence of dermal melanocytes in two cases cannot be explained because normally the dermis contains no melanocytes. Further studies concerning the role of iron or inflammatory cytokines on the development of dermal melanocytes should be conducted.
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