SUMMARY Pure tubercular osteomyelitis without joint involvement is rare and easily missed. Moreover the lesion is common in spine and large joints like hip and knee. The involvement of isolated metatarsal has been described rarely, only as few sporadic case reports. We present one such case of isolated first metatarsal involvement in an 8-year-old child who presented with chronic pain in left foot for over 6 months. The X-rays suggested a lytic lesion and lesion was confirmed on histopathology and acid-fast bacteria staining. The patient was treated with multidrug antitubercular chemotherapy. The results were excellent with complete healing of the lesion.
BACKGROUND Tuberculous bacilli have lived in symbiosis with mankind since time immemorial. Recent times have seen an increase in the incidence for a number of reasons. A few of the hypothesised causes include an increase in the incidence of HIV, greater use of immunosuppressive drugs and the emergence of multidrug resistant bacilli. Osteoarticular tuberculosis accounts for 1–3% of all tuberculosis cases.1 The disease usually involves spine and large joints like hip. Pure tubercular osteomyelitis is rare and is often missed. The literature review suggests an incidence of less than 0.5% for metatarsal osteomyelitis.1 The lesion is common in tarsal bones and usually involves the neighbouring joint. However, we present one such report involving only first metatarsal without any joint involvement.
CASE PRESENTATION An 8-year-old boy with a 6-month history of pain in his left foot presented to our outpatient department. The pain was localised over the first metatarsal, deep aching in character, had increased in intensity in past 6 months, was aggravated on walking and decreased but never disappeared with rest and over-the-counter analgesics. The boy had taken on and off non-steroidal anti-inflammatory drug (NSAID) and broad spectrum antibiotics without any relief. There was no history of constitutional symptoms. Patient’s mother had history of pulmonary Koch’s and child was immunised with BCG vaccine. On examination, there was tenderness on the dorsal aspect of first metatarsal. No sinus was seen. The skin was normal and minimal swelling was present over dorsomedial aspect of first metatarsal. Range of movement at ankle, Lisfranc and Chopart joints were normal. No regional lymphadenopathy
was seen. Chest examination was essentially normal.
INVESTIGATIONS Routine blood investigations revealed anaemia (haemoglobin 9.8 g%) with elevated erythrocyte sedimentation rate (ESR) of 45 mm/h. Mantoux was positive with maximum induration of 21 mm×19 mm. X-ray of the foot showed an eccentric welldefined lytic lesion, with surrounding osteopenia, no periosteal reaction and no articular involvement (figure 1). Trucut needle biopsy was performed and material was sent for pus culture and sensitivity, acid-fast stain and histopathology. The culture showed no growth; however, acid-fast bacteria stains were positive and histopathology showed giant cell granuloma with central caseous necrosis confirming the diagnosis of tubercular osteomyelitis (figure 2).
DIFFERENTIAL DIAGNOSIS A bony pain not relieved with analgesics should arouse a suspicion of infection or neoplasia. Lack of any periosteal reaction with no new bone
Figure 1 Plain anterioposterior radiograph showing eccentric lytic lesion in first metatarsal in skeletally immature foot.