5.1. Mucosal involvement: dry eyes
The tear film plays an essential role in promoting ocular surface integrity, defending against micro-bial challenge and preventing visual acuity. These functions, in turn, are extremely dependent upon the composition and stability of the tear-film structure. This includes an underlying mucin foundation (derived from globet cells and conjunctival- and corneal epithelial cells), a middle aqueous component (secreted primarily by lachrymal gland acinar and ductal epithelial cells) and an overlying lipid layer (originating from the meibomian glands). In pSS, due to the lymphocyte infiltration of lachrymal glands, a progressive decrease of the tear film, and especially of its aqueous component, develop and lead to a keratocongiuntivits sicca (KCS). The ocular surface disorder is then associated with a serious corneal disease affecting the lubrification and the homeostasis of the corneal surface (Rolando, 2001). Ocular irritation, burning, foreign body sensation and the need to keep the eye closed are the most common symptoms in patients with dry eye. Photophobia, pain, heavy eye and blurred vision may also be commonly described. Moreover, the cornea becomes irregular on the surface and the barrier activity of the epithelium may be impaired. Because of the failure of this barrier, frequent complications may arise, including ocular infections, keratitis and sometimes melting of the cornea or perforations (Rolando, 2001). Dry eyes disease is accompanied by an increase in the presence of inflammatory cytokines such as IL-1 b, which may play a key role in the patho-genesis and in perpetuation of KCS (Solomon et al., 2001). An interesting hypothesis is that IL-1b might contribute to a loss of corneal sensitivity, causing an interruption of the nerve impulse stimulation to the lachrymal gland, which in turn produces less fluid tears and an amount of tears rich of proinflammatory cytokines. As a consequence, the secretion of the lachrymal gland will inflame the ocular surface, keeping the vicious cycle going on (Rolando, 2001). This hypothesis of the diseased ocular surface that could further depress tear secretion, may justify the steady state situation of the tear gland function in pSS KCS during a long-term follow-up, compared with better prognosis in other forms of KCS (Kruize et al., 1997).
5.2. Mucosal involvement: dry mouth
Saliva, with its proteins and mineral salts, carries out many essential functions from the lubrification of the oral mucosa, to the contribution in initiating the digestive process, to soft tissue repair and the teeth remineralization. Moreover, saliva contains different antibacterial, antiviral and antimycotic agents, which are implicated in innate immunity and defence. These agents balance oral flora and inhibit bacterial colonization of teeth and soft tissue, by modulating the adherence of microorganisms (Soto-Rojas and Kraus, 2002). The main consequence of hyposalivation is the constant feeling of dry mouth (xerostomia), with a wide spectrum of subjective symptoms, varying from burning mouth to difficulties while swallowing and chewing dry foods, sensitivity to spicy foods, altered taste, speech difficulties and increased liquid intake. Dryness of the mouth is the most common complaint in pSS patients, reported by 98% and assessed as moderate to severe in 90% of the cases (Lundstrom and Lundstrom, 1995). Dental decay, in the border of teeth as well as in radicular sites, and oral infections are also commonly observed and oral mucosa may appear affected by recurrent mucositis, and ulcers (Soto-Rojas and Kraus, 2002). Mucosal changes may also include dry, cracked lips and alterations of the tongue surface, which may become furrowed and deep fissured (Soto-Rojas and Kraus, 2002). Chronic erythematous candidiasis has been described in 70-75% of patients (Daniels and Fox, 1992). The oral symptoms of pSS usually have an insidious onset and progress gradually, and nutrition may be compromised either by the hyposalivation itself or by the related dysphagia, and by an impaired clearance of esophageal acid leading to chronic esophagitis. Finally, a further complication associated with hyposalivation is sleep disturbance
Primary Sjogren's syndrome cutaneous manifestations Cutaneous vascular manifestation
Raynaud's phenomenon Purpura
Urticarial vasculitis Erythematous nodules
Erythema multiforme—like lesion/ erythema perstants Annular erythema
Non vascular cutaneous manifestations
Cutaneous B cell Lymphomas caused by nicturia, due to an increase in fluid intake (Daniels and Fox, 1992).
Cutaneous manifestations of pSS seem to be frequent and various, and are generally distinguished in vasculitic and non vasculitic lesions (Roguedas et al., 2004; Ramos-Casals et al., 2005). Table 2 summarizes the broad spectrum of cutaneous lesions. The number of literature studies specifically dedicated to skin involvement, nonetheless, is quite limited and skin lesions are minimized, overwhelmed by the most subjective painful lachrymal and salivary glands impairment (Roguedas et al., 2004). So far, only few studies on large numbers of patients have been published and this appears quite surprising, considering the clinical significance of cutaneous vasculitis and its correlations with lymphoma development (Bloch et al., 1965; Whaley et al., 1973; Veki et al., 1991; Bernacchi et al., 2004).
5.3.1. Cutaneous involvement: xerosis Skin dryness has been shown to be very common in Sjogren's syndrome with a frequency varying from 23 to 68% (Bloch et al., 1965; Whaley et al., 1973; Provost and Watson. 1992; Roguedas et al., 2004). The level of xerosis is significantly higher in the
Vasospastic phenomenon Leukocytoclastic /Mononuclear vasculitis Leukocytoclastic vasculitis Cutaneous vasculitis dermal perivascular lymphohistiocytic infiltrate
Dermal perivascular coat-sleeve-like lymphocytes infiltration
Sweat glands number reduction and dysfunction Erythemato-squamous lesion predisposed by xerostomia Erythematous lesion predisposed by xerophthalmia (rubbing) Lymphocitic infiltration of the sebaceous glands Loss of skin pigment due to autoimmune mechanism Malignant B cells proliferation primary than in the secondary form of the disease (Bernacchi et al., 2004). The most classical subjective symptoms of xerosis are non-specific pruritus, sensation of dryness, and a 'pin prick-like' feeling, which are associated with various objective signs such as rough, inelastic, hypotrophyc or fine scaling skin (Bernacchi et al., 2004). Scratching in response to the pruritus can lead to hyperpigmentation due to the repeated stimulation of the local melanocytes (Provost and Watson, 1992). The mechanism responsible for the skin xerosis in pSS patients has not been adequately elucidated (Provost and Watson, 1992). Cutaneous lubrification is provided basically by sebaceous glands, but sweat glands and apocrine glands may also contribute (Roguedas et al., 2004). An impairment of sweat glands is widely thought to be involved in pSS xerosis, since a decreased sweating has been reported in pSS patients (Whaley et al., 1973; Roguedas et al., 2004). A study by Katayama et al. (1995), aimed to assess the capacity of sweating in 49 patients affected by pSS, showed a statistically significant reduction in sweat volume of pSS in comparison with normal controls and patients affected by other dermatitis; sweating was induced by mental stimulation through hand grasping, measured with perspirometer and continuously recorded. Patients affected by other dermatitis displayed a decrease of sweating too, but their flow was not statistically lower than that of normal controls (Katayama et al., 1995). Other reports support the hypothesis of an impairment of eccrine sweat glands in pSS (Provost and Watson, 1992). Mitchell et al. (1987) performed a punch biopsy of the skin in a pSS patient with difficulty in perspiring and demonstrated a reduction of eccrine glands and ductal structures within reticular dermis and lymphocytes infiltration of all the remaining epithelial structures Studies of cholinergic-stimulated flow showed discordant results: some of them revealed a decreased sweating, while others presented no difference in the sweating response to pilocarpine between pSS patients and normal controls (Whaley et al., 1973; Katayama et al., 1995). The sweat secretion rate stimulated by iontophoresis was also studied in 22 pSS patients and 22 age- and sex-matched normal controls and no significant difference was found (Rees and Pal, 1989). Other possible explanations of the cutaneous dryness involve both sebaceous glands and apoc-rine glands abnormality. The hypothesis of an abnormal sebum production due to an absence of sebaceous glands may at least explain dryness of the hair (Provost and Watson, 1992). Apocrine glands dysfunction has also been mentioned to explain a deficient production of cerumen, associated with pruritus, scaling and crusting of the external ear canal in PSS patients (Henkin et al., 1972). Nonetheless, the function of apocrine glands is still poorly understood (Roguedas et al., 2004).
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