Biopsy-Proven Inflammatory Myopathy Emerges in Primary Sjögren’s Syndrome on Chronic Statin Therapy
Primary Sjögren’s syndrome usually announces itself through sicca symptoms, but the disease can travel well beyond the salivary glands. In this 63-year-old woman, the first dominant clue was not dryness alone, but an 8-month course of progressive, symmetric proximal muscle weakness that steadily eroded function. Her neurologic examination showed flaccid weakness without sensory loss, a pattern that pushes the differential toward a primary muscle process rather than a peripheral nerve disorder. The case became more complex because she was also taking a statin chronically, a background exposure that can blur the boundary between toxic myopathy, immune-mediated necrotizing myopathy, and connective tissue disease–associated muscle inflammation.
The diagnostic trap was immediate. Chronic statin therapy can seed the reflex assumption that muscle injury is medication-related, yet the combination of markedly elevated creatine phosphokinase, anti-HMG-CoA reductase positivity, and anti-Ro52 antibodies pointed toward an immune-mediated process rather than simple statin intolerance. Inflammatory myopathy is an uncommon extraglandular manifestation of pSS, and biopsy-proven disease is rarer still. This rarity matters at the bedside because a patient with sicca disease and muscle weakness may be routed down the wrong diagnostic path for months unless the muscle findings are interpreted as part of a systemic autoimmune syndrome.
Serology, Imaging, and Tissue Changed the Diagnosis
Laboratory testing showed marked creatine phosphokinase elevation, a biochemical signal of active muscle injury. Serology added a second layer of suspicion: anti-HMG-CoA reductase antibodies are strongly linked to immune-mediated necrotizing myopathy, particularly in the setting of statin exposure, while anti-Ro52 supports an autoimmune connective tissue disease context. The overlap of these findings created a narrow but important diagnostic corridor. A toxic statin myopathy alone would not usually explain this immunologic profile, and isolated pSS would not automatically account for the degree of muscle necrosis suggested by the downstream workup.
Magnetic resonance imaging of the thighs demonstrated diffuse myoedema. In practical terms, that pattern supports an active inflammatory or necrotizing muscle process and helps identify the tissue most likely to yield diagnostic histology. MRI cannot replace biopsy, but it can steer clinicians toward the right muscle and reduce the risk of a nondiagnostic sample. In a patient with long-standing weakness, imaging also helps distinguish diffuse inflammatory injury from a focal structural lesion or a neurogenic pattern of atrophy.
Muscle biopsy provided the decisive evidence. Histology showed myonecrosis, myophagocytosis, and lymphocytic infiltration, findings consistent with inflammatory myopathy. The presence of necrotic fibers alongside inflammatory activity fits an immune-mediated mechanism rather than isolated metabolic strain or uncomplicated drug toxicity. A biopsy result like this changes management immediately because it supports immunosuppressive treatment rather than simple discontinuation of a suspected medication.
Primary Sjögren’s Syndrome Was Confirmed Beyond the Muscle
Schirmer’s test and salivary gland biopsy established the underlying primary Sjögren’s syndrome. That step matters because the muscle disease did not arise in isolation; it occurred in the setting of a systemic autoimmune disorder with exocrine gland involvement confirmed by objective testing. Once pSS is proven, muscle weakness can no longer be treated as an incidental side effect or an unrelated neurologic complaint. The inflammatory myopathy becomes part of the patient’s autoimmune phenotype, even if it remains uncommon.
The case is a reminder that pSS is not confined to dryness symptoms. Extraglandular disease can involve multiple organs, and muscle disease belongs on that list even though it is seen infrequently. When weakness develops in a patient with pSS, clinicians need to separate three overlapping possibilities: direct autoimmune myositis, statin-associated immune-mediated necrotizing myopathy, and nonspecific statin intolerance. Each has different implications for treatment, prognosis, and relapse monitoring. Missing the immune-mediated subtype can leave a patient exposed to ongoing muscle injury if therapy is limited to stopping the statin alone.
Anti-HMGCR Positivity Raises the Stakes in Long-Term Statin Exposure
The presence of anti-HMG-CoA reductase antibodies gives this case particular clinical weight. Those antibodies are classically associated with statin-triggered autoimmune muscle disease, where muscle weakness and enzyme elevation persist even after the offending drug is withdrawn. In a patient with chronic statin exposure and autoimmune serologies, that result should prompt careful consideration of immune-mediated necrotizing myopathy rather than routine medication intolerance. The overlap with pSS creates diagnostic ambiguity, but it also explains why a broad immunologic panel was essential here.
A direct bedside consequence follows from this pattern. If a clinician assumes the weakness is purely statin-related and stops there, the active inflammatory process may continue unchecked. If the muscle disease is treated as isolated pSS without recognizing the anti-HMGCR signal, the contribution of statin-triggered autoimmunity may be underappreciated. The safest path is the one taken in this case: integrate serology, imaging, and tissue diagnosis before settling on the mechanism.
Why This Case Belongs in the Differential for Proximal Weakness
Progressive symmetric proximal weakness in an older adult demands a wide differential, but this case shows how autoimmune muscle disease can masquerade as something more common. The absence of sensory involvement argues against a neuropathic cause. The marked creatine phosphokinase elevation argues against a pure functional complaint or a noninflammatory deconditioning syndrome. MRI and biopsy then move the discussion from suspicion to proof.
The biology is coherent. Autoimmune injury to skeletal muscle can produce fiber necrosis, macrophage-mediated cleanup, and lymphocytic infiltration, which together generate the weakness and enzyme release seen in this patient. In the context of pSS, systemic immune dysregulation may set the stage for extraglandular involvement, while chronic statin exposure may amplify the likelihood of an anti-HMGCR–associated process. The result is a rare but clinically important collision of autoimmune disease and medication-associated immune myopathy.
Recognition of this overlap has immediate diagnostic value. Patients with pSS who develop new proximal weakness deserve evaluation beyond routine rheumatologic surveillance, especially when statins are part of the medication history. Muscle biopsy remains decisive when serology and imaging point toward inflammatory disease but do not fully define the mechanism.
The report leaves one central clinical issue unresolved in a broader sense: how often this dual phenotype is missed before biopsy confirms the diagnosis. What it does make clear is narrower and more actionable. In patients with pSS and chronic statin exposure, persistent proximal weakness with elevated muscle enzymes should trigger a full autoimmune myopathy workup rather than an assumption of simple drug toxicity.