Ayako Koura-Nishiura#, Kozo Yoneda#* and Yasuo Kubota

Department of Dermatology, Faculty of Medicine, Kagawa University, 1750-1 Ikenobe, Kitagun Mikicho, 761-0793 Kagawa, Japan. *E-mail: kyoneda@med.kagawa-u.ac.jp

#These authors contributed equally to this work and should be considered as first authors.

Accepted Oct 27, 2014; Epub ahead of print Oct 28, 2014

Purulent tenosynovitis is an infection within the tendon sheath (1). Staphylococcus aureus and Streptococcus are the most common causative organisms (1). The risk factors are an immunocompromised status such as HIV infection and diabetes mellitus (1). We describe purulent tenosynovitis caused by Streptococcus dysgalactiae subsp. equisimilis mimicking cellulitis. Diagnosis requires magnetic resonance imaging (MRI) and the culture of exudate fluid from the carpal tunnel.

CASE REPORT

A 48-year-old Japanese man suddenly developed fever (39.0°C) and painful skin eruption of the right wrist region on October 29, 2011. He had a history of diabetes mellitus for 12 years, controlled with insulin. Because tenderness persisted and flexion of the fingers gradually became difficult, he was admitted to our hospital on October 31, 2011. He had suffered no trauma to the skin. A physical examination revealed erythema of the wrist region and palm of his right hand. The right hand, extending from the wrist to the fingers, was erythematous, warm, and swollen, with marked induration and punctate bleeding (Fig. 1a). A tentative diagnosis of cellulitis was made. On October 31, 2011, he had a white blood cell count of 12,550/mm3 (normal range 4,700–8,700/m3) and a haemoglobin level of 9.9 mg/dl (normal 13.0–17.0 mg/dl). Immediately after hospitalisation, his blood results were: glucose: 163 mg/dl (normal 70–100 mg/dl); HbA1c: 7.9% (normal 4.6–6.2%); blood urea nitrogen: 30.9 mg/dl (normal 7.0–20.0 mg/dl); creatinine: 1.77 mg/dl (normal 0.70–1.30 mg/dl); aspartate transaminase (AST; SGOT): 18 U/l (normal 10–35 U/l); alanine transaminase (ALT; SGPT): 10 U/l (normal 5–40 U/l); alkaline phosphatase: 242 U/l (normal 100–340 U/l); and total bilirubin: 0.5 mg/dl (normal 0.1–1.2 mg/dl); total protein: 7.8 mg/dl (normal 6.5–8.2 mg/dl); antistreptolysin O: 506 (normal ≤ 210 U/ml); antistreptolysin K: 5,120 (normal ≤ 1,280 U/ml). Other relevant negative tests included blood smears for malaria, cold agglutinin, antinuclear antibody (ANA), and hepatitis-associated antigens and antibody.

Histological examination showed mild subepidermal oedema and red blood cell extravasation into the dermis (Fig. 1b, c). Emergent MRI revealed exudate fluid retention around the tendon sheaths in the carpal tunnel (Fig. 2a). The diagnosis was changed to purulent tenosynovitis. Surgery for carpal tunnel release was immediately conducted. Cultures of exudate fluid from the carpal tunnel yielded the growth of S. dysgalactiae subsp. equisimilis. A histological specimen from the tenosynovitis lesion revealed many neutrophils infiltrating between the interstitial collagen in the synovium (Fig. 2b, c). Intravenous drip infusion of clindamycin and penicillin G was started. The lesion healed promptly, without any inflammation or drainage. He also received extensive rehabilitation and recovered the function of his forearm, wrist, and hand. He was discharged on January 10, 2012.

Fig. 1. The right hand, extending from the wrist to the fingers, was erythematous, warm, and swollen, with marked induration and punctate bleeding (a). Haematoxylin-eosin stain demonstrated mild subepidermal oedema and red blood cell extravasation INTO the dermis. (b) × 2; (c) × 100.

Fig. 2. Emergent magnetic resonance imaging revealed exudate fluid retention around the tendon sheaths in the carpal tunnel (arrow) (a). A histological specimen from the tenosynovitis lesion revealed many neutrophils infiltrating between interstitial collagen in the synovium. (b) × 4; (c) × 100.

DISCUSSION

Due to clinical signs such as erythema, heat, swelling, and tenderness, we first diagnosed this patient with cellulitis (2). However, sites of predilection for cellulitis are the lower legs and face (3). In addition, the erythema was fainter than typical cellulitis and the patient complained of difficulty in flexion of the fingers of his right hand. Thus, we conducted emergent MRI and found exudate fluid retention around the tendon sheaths in the carpal tunnel. We believe the emergent MRI was of marked importance in curing this patient.

Purulent tenosynovitis caused by S. dysgalactiae subsp. equisimilis has not been reported. This pyogenic β-haemolytic Streptococcus is emerging as a human pathogen with a similar disease profile to S. pyogenes (4–6). While it primarily presents as skin and soft-tissue infections, including cellulitis and necrotising fasciitis, S. dysgalactiae subsp. equisimilis sometimes causes endocarditis, rheumatic fever, and streptococcal toxic shock-like syndrome. Hence, there is a need to accurately identify this invasive subspecies of Streptococcus. We used a classical culture method, a swab from the exudate fluid and streaking on blood agar plates, to identify S. dysgalactiae subsp. equisimilis. There is a report on identifying this subspecies with the aid of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF) (7, 8). As our patient was immunocompromised due to severe diabetes mellitus, this subspecies might have grown instead of S. pyogenes, which is most frequently identified in cellulitis. An appropriate diagnostic imaging system and rapid bacterial cultures are mandatory for a correct diagnosis because skin eruption is sometimes the first sign of soft tissue infection which may later become severe.

ACKNOWLEDGMENTS

We are grateful to Dr. Yuko Ono, MD (Department of Radiology, Faculty of Medicine, Kagawa University) who evaluated the MRI images. This work was supported by grants from the Ministries of Health, Labour, and Welfare and Education, Culture, Sports, Science and Technology of Japan.

The authors declare no conflict of interest.

REFERENCES