Pruritus, which is defined as an itching sensation that elicits a desire to scratch, is the most common cutaneous condition. Pruritus is considered chronic when it lasts for more than 6 weeks.1 Etiologies implicated in chronic pruritus include but are not limited to primary skin diseases such as atopic dermatitis, systemic causes, neuropathic disorders, and psychogenic reasons.2 In approximately 8% to 35% of patients, the cause of pruritus remains elusive despite intensive investigation.3 The mechanisms of itch are multifaceted and include complex neural pathways.4 Although itch and pain share many similarities, they have distinct pathways based on their spinal connections.5 Nevertheless, both conditions show a wide overlap of receptors on peripheral nerve endings and activated brain parts.6,7 Fibromyalgia, the third most common musculoskeletal condition, affects 2% to 3% of the population worldwide and is at least 7 times more common in females.8,9 Its pathogenesis is not entirely clear but is thought to involve neurogenic inflammation, aberrations in peripheral nerves, and central pain mechanisms. Fibromyalgia is characterized by a plethora of symptoms including chronic widespread pain, autonomic disturbances, persistent fatigue and sleep disturbances, and hyperalgesia, as well as somatic and psychiatric symptoms.10
Fibromyalgia is accompanied by altered skin features including increased counts of mast cells and excessive degranulation,11 neurogenic inflammation with elevated cytokine expression,12 disrupted collagen metabolism,13 and microcirculation abnormalities.14 There has been limited research exploring the dermatologic manifestations of fibromyalgia. One retrospective study that included 845 patients with fibromyalgia reported increased occurrence of “neurodermatoses,” including pruritus, neurotic excoriations, prurigo nodules, and lichen simplex chronicus (LSC), among other cutaneous comorbidities.15 Another small study demonstrated an increased incidence of xerosis and neurotic excoriations in females with fibromyalgia.16 A paucity of large epidemiologic studies demonstrating the fibromyalgia-pruritus connection may lead to misdiagnosis, misinterpretation, and undertreatment of these patients.
Up to 49% of fibromyalgia patients experience small-fiber neuropathy.17 Electrophysiologic measurements, quantitative sensory testing, pain-related evoked potentials, and skin biopsies showed that patients with fibromyalgia have compromised small-fiber function, impaired pathways carrying fiber pain signals, and reduced skin innervation and regenerating fibers.18,19 Accordingly, pruritus that has been reported in fibromyalgia is believed to be of neuropathic origin.15 Overall, it is suspected that the same mechanism that causes hypersensitivity and pain in fibromyalgia patients also predisposes them to pruritus. Similar systemic treatments (eg, analgesics, antidepressants, anticonvulsants) prescribed for both conditions support this theory.20-25
Our large cross-sectional study sought to establish the association between fibromyalgia and pruritus as well as related pruritic conditions.