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Autoantibodies (AAb), typically detectable in sera of patients with systemic sclerosis (SSc), are more or less specific and directed against DNA topoisomerase I (Scl-70), centromeric (CENP-B) and nucleolar (fibrillarin, RNA polymerases, Th/To, PM/Scl) antigens and are found also in mixed connective tissue diseases or even before disease manifestation.1,2 In rare cases, AAb to cell cycle associated antigens of the centriole/centrosome, the nuclear mitotic apparatus, the stem body, the cleavage furrow, and the midbody region can be found.3–,5 In the mid-1980s two separate groups described anti-midbody antibodies (aMB) in five patients with SSc and in one patient with Raynaud’s syndrome.4,5 The target antigen(s) of aMB are still unknown proteins of the cleavage furrow and the midbody region of dividing cells and are detected by indirect immunofluorescence on tumour cell monolayer (HEp-2).
A 61 year old woman first presented in 1999 with a history of more than 15 years’ Raynaud’s syndrome. A first examination showed skin sclerosis with periorally intensified radial skinfolding, reduced mouth opening with an extensive frenulum sclerosis (figs 1A and B⇓), xerostomia, and classic cutaneous sclerosis with diminished skin foldability over all fingers. There were no scarred healed finger pad ulcerations, calcinosis, or telangiectasias and only discrete changes of the nail fold. Clinical examination and laboratory tests showed normal results. Indirect immunofluorescence showed aMB at high titres of 1/2560, but no other AAb, were detectable (fig 2⇓). Further examinations (radiographs, high resolution computed tomography, thorax, capillary microscopy, oesophagoscintigraphy, gastroscopy, pulmonary function tests, echocardiography, abdominal sonography) did not show pathological findings.
An updated organ staging was performed in May 2004. No internal organ manifestation of SSc or a malignant disease could be found.
For the classification of definite SSc, American College of Rheumatology criteria are used.7 However, these criteria are very often too insensitive for early SSc and cannot be used for variants of SSc such as “sclerosis sine scleroderma”.8 Also, according to the LeRoy criteria— a scleroderma classification that depends on the extent of skin involvement—our patient does not fulfil the demanded criteria.9 All findings merged, there is no further evidence of an internal organ involvement encompassed by SSc apart from the mucocutaneous signs.
AAb against antigen(s) of the midbody region are rarely described. They seem to be associated with SSc and Raynaud’s syndrome and were found in one patient with primary hepatocellular carcinoma.4–,6 The data published in the mid-1980s give no information about the duration of the Raynaud’s syndrome. Also in the case of idiopathic Raynaud’s syndrome the patient was not followed up for a longer period to exclude a later manifestation of SSc. Many relevant questions—for example, the prevalence of aMB in a normal population, their association with other diseases, and the antigens targeted, have not been answered up to now. As we do not routinely examine for aMB, it can be assumed that patients with aMB may very often remain unrecognised. The results of Fritzler et al, as well as our own examinations on more than 1000 blood donors (unpublished results), demonstrate that aMB are not detectable in people without disease and therefore seem to be disease associated.10
Because of the typical skin changes in our patient who had 15 years of Raynaud’s syndrome in combination with a special autoantibody response, a special limited or incomplete, benign variant of SSc, is suggested.
The role of aMB as a predictive factor of such a minimal variant of SSc remains unclear. Only an evaluation of these antibodies in combination with a follow up of as many patients as possible could provide further answers to these questions.