What is the most likely diagnosis in a 77‑year‑old woman with progressive painful symmetric swelling of the feet and ankles with groove sign, eosinophilia, low‑titer antinuclear antibody, and biopsies showing eosinophilic fasciitis of the fascia and morphea of the skin?

Eosinophilic Fasciitis with Overlapping Morphea

The most likely diagnosis is eosinophilic fasciitis with coexisting morphea, a well-recognized overlap syndrome characterized by symmetric painful swelling of the extremities with groove sign, peripheral eosinophilia, and histologic confirmation showing both fascial inflammation with eosinophils and dermal sclerosis. 1, 2

Diagnostic Confirmation

This patient's presentation fulfills the characteristic clinical, laboratory, and histologic triad required for eosinophilic fasciitis diagnosis:

Clinical Features

• Symmetric circumferential swelling and induration of bilateral feet, ankles, arms, and back with the pathognomonic "groove sign" (linear furrows over superficial vessels) is the hallmark clinical finding of eosinophilic fasciitis 1, 2
• Peau d'orange appearance of the skin represents the characteristic orange-peel texture seen in this condition 2
• Progressive pain and joint contractures with limited movement are typical complications resulting from fascial inflammation and restriction 1, 3
• The distal-to-proximal progression involving extremities and trunk matches the classic distribution pattern 4, 3

Laboratory Findings

• Peripheral eosinophilia is present in 60-93% of cases, though not mandatory for diagnosis 2, 5
• Low-titer ANA (1:80) and smooth muscle antibody (1:80) are consistent with eosinophilic fasciitis, where antinuclear antibodies are commonly absent or low-titer 2
• Normal ESR and CRP do not exclude the diagnosis, as inflammatory markers can be variable 4

Histologic Confirmation

• Full-thickness fascia biopsy showing eosinophilic infiltration with fascial thickening is the gold standard and was obtained from the left calf 1, 5
• Skin biopsies demonstrating morphea features (thickened collagen bundles, dermal sclerosis, loss of adnexal structures) confirm the overlap syndrome 2, 3
• Coexisting morphea plaques occur in almost 50% of eosinophilic fasciitis patients, making this overlap well-documented 3

Critical Differential Diagnoses Excluded

Systemic Sclerosis

• Absence of Raynaud phenomenon, sclerodactyly, and digital ulcers argues against systemic sclerosis 1
• Negative anti-SCL-70 and anti-centromere antibodies effectively exclude systemic sclerosis 5
• Sparing of hands and face is typical of eosinophilic fasciitis, whereas systemic sclerosis characteristically involves these areas 1, 5

Necrotizing Fasciitis

• Two-year chronic progressive course excludes necrotizing fasciitis, which presents acutely with rapid progression over hours to days 6, 7
• Absence of systemic toxicity, fever, or altered mental status rules out this life-threatening infection 6, 7
• No skin necrosis, bullae, or crepitus further excludes necrotizing fasciitis 7

Eosinophilia-Myalgia Syndrome

• No history of L-tryptophan ingestion excludes this toxic epidemic fasciitis syndrome 1, 5

Hypereosinophilic Syndrome

• Lack of cardiac involvement (no cardiomyopathy on evaluation) argues against hypereosinophilic syndrome, where cardiac disease is a major feature 6
• Predominant fascial and dermal involvement rather than multi-organ eosinophilic infiltration distinguishes eosinophilic fasciitis 1

Important Diagnostic Pitfall

The trace monoclonal band on SPEP requires follow-up, as peripheral T-cell lymphomas can present with eosinophilic fasciitis-like features and must be definitively excluded with repeat testing or bone marrow evaluation if the band persists 1, 5

Treatment Approach

First-Line Therapy

• Oral prednisone 1 mg/kg/day (typically 40-60 mg daily) is the standard initial treatment and should be initiated immediately 1, 4, 5
• Aggressive physical therapy and myofascial techniques must be started concurrently to prevent permanent joint contractures and maintain mobility 2, 3

Second-Line Therapy for Inadequate Response

• Add methotrexate 15-25 mg weekly if response to corticosteroids alone is unsatisfactory after 4-8 weeks, particularly given the coexisting morphea-like lesions 1, 3
• Initial combination therapy with corticosteroids plus methotrexate may be most beneficial based on emerging evidence 3

Monitoring for Complications

• Screen for eosinophilic colitis if gastrointestinal symptoms develop, as this rare association has been reported with eosinophilic fasciitis 2
• Repeat SPEP in 3-6 months to ensure the monoclonal band resolves and does not represent evolving lymphoproliferative disease 2

Corticosteroid Tapering

• Taper prednisone slowly over 6-12 months once clinical improvement is achieved, as premature tapering risks relapse 4, 5

Prognosis

Some patients experience spontaneous remission, but most require prolonged immunosuppressive therapy to achieve disease control and prevent permanent disability from joint contractures 4, 5