Nontuberculous Mycobacterial Arthritis of the First Metatarsophalangeal Joint in a Young Immunocompetent Adult: An Interesting Case Report

Sir,

Nontuberculous mycobacterial (NTM) infections involve the musculoskeletal system in approximately 5–10% of the patients.[1] The most common manifestation of NTM infections is osteomyelitis. However, swelling and lytic lesions of the affected bone are rarely seen.[2]

A 19-year-old male presented with pain and swelling of the right great toe since three months. No punctured wound was reported. Past history and family history were not contributory. A plain roentgenogram of the right foot revealed [Figure 1] a lytic lesion at the base of the first metatarsal bone, with arthritic changes of the first metatarsophalangeal joint, surrounding soft tissue swelling, and erosion of the base of the first phalanx. The patient was empirically started with a combination of ceftriaxone 1 g/day and netilmicin 150 mg twice/day, administered intravenously for 15 days, and subsequently an oral therapy of ciprofloxacin 250 mg twice/day for one month with regular follow-up. However, the symptoms continued to aggravate and did not show any improvement. His erythrocyte sedimentation rate was 30 mm/hour. The chest roentgenogram was normal. An Enzyme-Linked Immunosorbent Assay test for human immunodeficiency virus (HIV) detection was negative. A surgical incision and drainage procedure was performed. The debrided synovial tissue was submitted for histopathology and microbiology examinations. The microscopic examination revealed multiple well-formed, epithelioid granulomas, without caseous necrosis [Figure 2]. The Ziehl Neelsen stain was negative for acid fast bacilli. The culture for mycobacterium tuberculosis was negative. A tuberculin skin test was negative. The Mycobacterium COMBO test for detection of IgM antibodies against two highly purified antigens, derived from the Mycobacterium, namely, the cell wall and 38kDa antigens, was elevated (1.03 index value). A repeat culture from the lesion was performed, which identified the mycobacterium avium complex (MAC) species. A final diagnosis of NTM arthritis of the right first metatarsophalangeal joint, caused by MAC species, was made based on the correlation of the clinical features, and the radiology, histopathology, and microbiology findings. The patient received a one-year course of Azithromycin 1000 mg/day, Ethambutol 15 mg/kg/day, rifabutin 150 mg/day, along with indomethacin, which resulted in resolution of the lesions in the patient, with follow-up.

Figure 1.

Lytic lesion (Double arrowhead) at the base of the first metatarsal bone with surrounding soft tissue swelling and erosion of the base of the first phalanx (Single arrowhead)

Figure 2.

(H and E, x400): Well-formed epithelioid granulomas with Langhans giant cells and necrosis

Unlike M. tuberculosis, NTM is not transmitted from person to person.[1,2] Most osseous infections are caused by Mycobacterium kansasii and Mycobacterium scrofulaceum.[3] With NTM infection, the onset of nonspecific symptoms is indolent and usually includes local pain and swelling, joint stiffness, low-grade fever, sweats, chills, anorexia, malaise, and weight loss. The triad of Phemister, consisting of osteoporosis, peripheral marginal erosions, and slowly progressing destruction of the articular cartilage, characterizes mycobacterial arthritis.[4] On account of their infrequent occurrence and difficulty in identification, with a lack of specificity of imaging findings, a heightened clinical suspicion of slow-growing nonchromogenic mycobacterial species in cases of arthritis is needed, when a routine bacterial culture or histopathological findings do not readily identify an organism.[5] The prescribed management in the setting of NTM infection is the combination of different antituberculous drugs and antibiotics, along with surgical drainage, which was administered to our patient, resulting in a favorable outcome.