Sonographic appearance of pseudopodagra in Behçet's disease

Dear Editor,

Arthritis of the first metatarsophalangeal (MTP) joint of a different cause than gout is identified by the term pseudopodagra. Although the majority causes of pseudopodagra are deposits of other micro crystals, there has been other rare cause, such as Behcet's disease.^1,2 We present the case of a patient with a pseudopodagra due to Behcet's disease.

A 43-year-old female patient suffering from Behcet's disease for 10 years presented to the emergency department (ED) with discomfort in her right MTP joint. The onset was characterized by acute pain, swelling, erythema, tenderness, and limitation of movement of the first MTP joint of the right foot. The patient denied any fever, chills, trauma, urethral symptoms, conjunctivitis, or history of gout. She had a past several attacks affecting oligoarticular involving knees and ankles. There was no family history of rheumatic disease. On physical examination, she was afebrile and all vital signs were normal. The area overlying her first MTP joint was red, hot, swollen, and exquisitely tender to touch and to any movement of the great toe.The skin was not disrupted, and no lymphangitis or adenopathy was present. All other joints were normal, as was the remainder of the physical examination. Patient refused arthrocentesis procedure. We preferred ultrasound imaging as a first line imaging technique instead of magnetic resonance imaging in order to save time. Grayscale ultrasound examination of dorsal aspect of 1st MTP showed marked synovial thickening (arrows) and minimal synovial fluid (arrowhead) (Fig. 1 A). There was no gouty tophus at the MTP joint. On power doppler imaging increased color signals are seen within the hyperthrophic synovium consistent with hyperemia (Fig. 1B). On left side, minimal concentric proliferation of synovial lining cell tissue and synovial fluid (arrowhead) was seen (Fig. 2A). There were no color signals within the synovium on the 1st MTP of the left foot ( Fig. 2B). Preliminary diagnosis was pseudopodagra rather than metatarsophalangeal arthritis because significant extra-articular soft tissue changes were evident. Soft tissue changes can occur with rheumatological diseases including familial Mediterranean fever (FMF)'s joint attack, acute rheumatic fever (ARF), calcium pyrophosphate dihydrate (CPPD) crystal deposition disease and gout. Rheumatoid arthritis also commonly affects the MTP joints, although this is characterized with a symmetric polyarthritis, making it a rare differential diagnosis. In our patient FMF and ARF were not considered as a relevant differential diagnosis because those diseases were inconsistent with clinical and laboratory findings. Sonographic features of CPPD deposits depend on the amount and distribution, varying from homogeneously punctate pattern or sharply defined hyperechoic bands within the articular cartilage or floating in synovial fluid to rounded or amorphous-shaped hyperechoic areas in fibrocartilage.³ In the gout, monosodium urate crystals tend to result in hyperechoic enhancement on the superficial margin of hyaline cartilage. The most frequent ultrasonographic characteristic of gouty tophi is hyperechogenicity.⁴ In addition, tophi are generally heterogeneous, with poorly defined contours, multiple grouped and surrounded by an anechoic halo.^5,6 However, these sonographic findings were not seen in our patient.

Fig. 1
A, Grayscale ultrasound examination of dorsal aspect. B, Power doppler imaging increased color signals.

Fig. 2
A, Minimal concentric proliferation of synovial lining cell tissue and synovial fl uid. B, There were no color signals within the synovium.

Musculoskeletal ultrasound has significant potential usefulness for the diagnosis, severity assessment, decision to treat, and treatment efficacy assessment of patients with unknown etiology arthritis.⁷ The ultrasound examination as a fast, reproducible diagnostic method has now become part of the routine diagnosis in rheumatological disorders.

REFERÊNCIAS

• ¹
  Benamour S. Pseudopodagra in Behçet's disease. Rev Rhum Engl Ed 1995;62: 2153-4.
• ²
  Giacomello A, Sorgi ML, Zoppini A. Pseudopodagra in Behçet's syndrome. Arthritis Rheum 1981; 24: 5750-1.
• ³
  Lin YY, Wang TG, Li KJ, Lew HL. Imaging Characteristics of Calcium Pyrophosphate Dihydrate Crystal Deposition Disease. Am J Phys Med Rehabil 2012; Http://dx.doi.org/10.1097/PHM.0b013e31825566aa.
  » Http://dx.doi.org/10.1097/PHM.0b013e31825566aa
• ⁴
  Fernandes EA, Lopes MG, Mitraud SA, Ferrari AJ, Fernandes AR. Ultrasound characteristics of gouty tophi in the olecranon bursa and evaluation of their reproducibility. Eur J Radiol 2012; 81: 2317-23.
• ⁵
  de Ávila Fernandes E. Kubota ES. Sandim GB. Mitraud SA. Ferrari AJ. Fernandes AR. Ultrasound features of tophi in chronic tophaceous gout. Skeletal Radiol 2011;40:3309-15.
• ⁶
  de Ávila Fernandes E. Sandim GB. Mitraud SA. Kubota ES. Ferrari AJ. Fernandes AR. Sonographic description and classification of tendinous involvement in relation to tophi in chronic tophaceous gout. Insights Imaging 2010; 1:3143-8.
• ⁷
  Howard RG, Pillinger MH, Gyftopoulos S, Thiele RG, Swearingen CJ, Samuels J. Reproducibility of musculoskeletal ultrasound for determining monosodium urate deposition: concordance between readers. Arthritis Care Res (Hoboken):2011;63:101456-62.

Publication Dates

• Publication in this collection
  Jan-Feb 2014