Twisted collagen fibrils in acrocyanosis

ARTICLE

Acrocyanosis presents as a dusky discoloration of the hands, sometimes involving the feet. This characteristic skin sign is caused by the failed regulation of the terminal blood flow in the subpapillary plexus of the dermis. Acrocyanosis is one of the vascular signs for Ehlers-Danlos syndrome (EDS) and for some of the acquired systemic diseases. However, there are patients presenting discoloration as the sole symptom. This disorder has been known as essential acrocyanosis (EA). Previously, the authors have reported that a female patient with EA presented twisted collagen fibrils (TCF) in normal skin [1]. TCF have been constantly found in the normal skin of EDS patients in the various clinical subtypes [2-4]. This study is intended to evaluate the significance of TCF in patients with acrocyanosis of various causes and to discuss the relation of EA to EDS.

Material and methods

Patients

Thirteen patients with persistent dusky discoloration of the hands, 2 of them presenting the discoloration over the wrists, were randomly selected in the out-patients. Clinical diagnosis of those 13 patients was 6 acrocyano-sis, 1 EDS, 2 acrocyanosis with livedo reticularis, 1 livedo reticularis, 1 acrocyanosis with vasculitis, 1 acrocyanosis in sclerodactyly, and 1 Raynaud's disease. The clinical diagnosis, symptoms, family histories, presence of TCF and vascular changes are listed in the Table.

Methods

Skin specimens were removed from normal skin in the left elbow by 3 mm punches and prepared for routine electron microscopy. Semithin sections were stained with 0.5% toluidin blue and studied by light microscopy. Neither perivascular cell infiltrate nor vasculitis was demonstrated in the biopsy specimens. Ultrathin sections were cut in both papillary and reticular dermis and stained with uranyl acetate and lead citrate. An JEOL 100 CX electron microscope was used at 80 KV.

Results

Compared with normal collagen fibril bundles, which consist of straight fibrils in parallel array (Figs. 5a, b), the dermis of acrocyanosis patients often presents the collagen fibrils in bent and wavy shapes and in parallel, distorted and swirl-formed arrays. The fibrils form straight or arch-formed bundles (Figs. 1, 2, 3). The thicknesses of the collagen fibrils in the patients were either normal, ca 80 nm across, or varied mostly by thinner fibrils (Figs. 2, 3 compared with Figs. 5a and b). TCF were found in the dermis of 10 patients ; No. 1, 3, 4, 5, 6, 7, 8, 9, 10, 11 (Table). TCF were identified by the characteristic figures of the flower-shaped, polygonal and zigzag-bordered cut-surfaces in the cross sections (Fig. 2 compared to Fig. 5a). In the longitudinal sections, TCF showed distinct twistings (Fig. 3, compared to Fig. 5b). TCF were usually thinner than normal collagen fibrils (Figs. 2, 3, 5a and b) and appeared in the disarrayed bundles.

Occasionally, thick flower-shaped TCF were found in the normal collagen fibril bundles. Axial periodicty of TCF was normal. TCF were not demonstrated in the dermis of 3 patients, No. 2, 12, 13 (Table). These patients showed normal collagen fibril bundles. Elastic fibers showed age-dependant but no pathological changes. Dermal glycosaminoglycans were not increased in number.

Small vessels in the subpapillary plexus showed narrow lumina and hypertrophic endothelial cells and pericytes in the patients No. 1, 3, 4, 5, 9 (Fig. 4, Table). The hypertrophic pericytes contained well-developed endoplasmic reticula. In patients No 4, 7, 8, 11, the vascular walls were tickened by multiple layers of the basal lamina (Table).

Discussion

Ultrastructurally, TCF have been found in the dermis of some inherited disorders of connective tissue, e.g. in the lesions of pseudoxanthoma elasticum [5], connective tissue nevi [6], primary systemic amyloidosis [7] and juvenile elastoma [8]. TCF have been also demonstrated in the normal dermis of the EDS patients, clinical subtypes I, II, III, IV, VI and VII [2-4, 8, 9], and also in the normal dermis of the EDS-supposed patients who presented mild and uncertain cardinal symptoms of EDS [10, 11]. In EDS type VII B, Watson et al [9] have demonstrated that the inherited deficiency of N-proteinase formed TCF. Recently, genetic linkages between TCF and collagen genes in EDS subtypes I/II and IV have been demonstrated [12, 13]. These findings suggested that TCF were the ultrastructural sign for inherited abnormalities in the formation of collagen fibrils.

TCF in the normal skin of EDS patients have been recognized ultrastructurally by the characteristic figures, i.e. distinct twistings in the longitudinal sections and flower-like, zigzag-bordered and polygonal forms in the cross sections. TCF have been studied in normal skin of the 65 hypermobile patients showing the Beighton's score index [14] BI 0-5 [10]. TCF have been found in 6 of 13 patients with BI 0, 18 of 20 with BI 1-2 and all 32 patients with BI 3-5. The patients with BI higher than 4-5 showed certainly the cardinal symptoms of EDS. The figures of TCF in those patients were flower-shaped in 16% of 65 patients and polygonal and zigzag-bordered in 74% of the patients. Individual patients often showed all three shapes of TCF, either single or combined [10]. Some of the normal, non hypermobile family-members in the EDS pedigree have also presented TCF in their normal skin [4]. Furthermore, when the present authors studied the dermis of the sun-protected areas of the randomly selected 47 adults without EDS-supposed symptoms, 2 of them contained TCF (unpublished data). Another example was that 2 of 48 lupus erythematosus patients with no clinical signs of EDS had TCF in the uninvolved dermis of the biopsy specimens (unpublished data). These facts imply that about 4% of the population have TCF, without showing any EDS-supposed clinical symptoms. In addition some patients had a few mild EDS-supposed symptoms, which they did not complain of, while they were carrying TCF [4, 10]. Tentatively the present authors have called those 2 groups of persons as TCF-carriers. The TCF-carriers could not be diagnosed as EDS, since diagnosis of EDS was made by clinical symptoms [11], however, they should be included in the disease category of EDS. It seemed unreasonable to force those patients into one of the subtypes of EDS. Biochemical analysis of enzymes in the collagen metabolism might confirm the clinical subtypes VI and VII, if the diagnosis of EDS was established clinically, while the majority of EDS patients belong to subtypes I, II, III. Recent studies of gene analysis for subtypes I, II and IV [12, 13] are expected to be a powerful technique in the near future.

Acrocyanosis was one of the vascular manifestations in EDS. The authors have found acrocyanosis in 11 of 84 patients with BI O-5 (about 12%), even in the patients with BI 0-1 [10]. These facts imply the possibility that acrocyanosis could appear as the sole clinical manifestation among the cardinal symptoms of EDS. EA could be explained as acrocyanosis being the sole symptom of the TCF-carrier. Besides EA, the authors have found that the TCF-carriers might have the potential for acute and chronic complications in other organs, e.g. juvenile intracranial beeding, diverticula of intestine, pelvic distraction and some other birth complications, chronic luxation and menisceal injuries [4, 10].

Of the 10 TCF positive patients in this study, No. 6 patient was EDS and No. 1, 3, 11 were supposed to be EDS. Three patients, No. 4, 5, 9 were EA. Patient No 9 also suffered from Raynauld's phenomenon. Possibly, TCF predisposes for Raynaud's disease (No. 10). Hyperglobulinemia of cold aggulutinin syndrome [15] and antiphospholipid syndrome [16] also revealed acrocyanosis, however, no TCF have been examined in those studies. Patients No 7 and 8 were not conclusive for EA, since there were no knowledges of TCF production by gammaglobulinemia. Similar questions probably arise from the acrocyanosis in Burkitt's lymphoma [17], extra-adrenal pheochromocytoma [18], lymphatic diseases [19], anorexia nervosa [20] and spinal cord injury [21]. For patients No. 3, 12, 13, acrocyanosis was presumed to be caused by unspecific inflammation, vasculitis and sclerodactyly, respectively.

Pericytes in the walls of the subpapillary vascular plexus have regulated the terminal blood flow and these cells also secreted collagen [22]. The present findings assumed that the inherited dysfunction of the pericytes might introduce acrocyanosis and TCF in EA.

CONCLUSION

EA is probably a vascular disorder of the skin in the hands of the TCF-carrier. The vascular dysfunction may be the consequence of a hereditary dysfunction of the pericytes in the subpapillary vascular plexus.

Acknowledgement

The authors thank associate professor Poul Halberg, Rheumatology department Hvidovre Hospital for the comments. This study was supported by grants from the Danish Rheumatism foundation, Gerda and Aage Hænsch's foundation and Terd & Ellen Hindsgaard's foundation.

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