Calcific myonecrosis following snakebite

Calcific myonecrosis is a rare condition and less than 50 cases have been reported in the English literature. It was first described by Gallie and Thompson in 1960 as a late sequela of compartment syndrome.1 Although a hypothesis for the development of this complication was proposed by Janzen et al. in 1993 and O’Keefe et al. in 1995, the exact physiological mechanism is not fully understood.2,3 The condition is characterised by muscle necrosis of an entire osteofacial compartment with central liquefaction and peripheral calcification. The clinical and radiographic findings can be misdiagnosed as a soft tissue sarcoma.4-6 Differential diagnosis includes synovial sarcoma and soft tissue osteosarcoma as well as benign conditions like myositis ossificans, dermatomyositis, tumoral calcinosis and calcific tenosynovitis (Table I).5 We report two similar cases of calcific myonecrosis of the anterior compartment of the lower leg following snakebites and review the available literature on this rare condition. Case report


Introduction
Calcific myonecrosis is a rare condition and less than 50 cases have been reported in the English literature.It was first described by Gallie and Thompson in 1960 as a late sequela of compartment syndrome. 1Although a hypothesis for the development of this complication was proposed by Janzen et al. in 1993 and O'Keefe et al. in 1995, the exact physiological mechanism is not fully understood. 2,3he condition is characterised by muscle necrosis of an entire osteofacial compartment with central liquefaction and peripheral calcification.][6] Differential diagnosis includes synovial sarcoma and soft tissue osteosarcoma as well as benign conditions like myositis ossificans, dermatomyositis, tumoral calcinosis and calcific tenosynovitis (Table I). 5 We report two similar cases of calcific myonecrosis of the anterior compartment of the lower leg following snakebites and review the available literature on this rare condition.

Case report
Two similar cases were managed at our unit during the same year.These cases involved female patients aged 62 and 81 years respectively, who both reported a painless, progressively enlarging mass in the anterolateral aspect of

Abstract
Calcific myonecrosis is a rare condition and is believed to be a late sequela of untreated compartment syndrome.Patients usually present with a progressively enlarging mass, years after the initial injury, that can be misdiagnosed as a soft tissue sarcoma.Calcific myonecrosis following snakebite is extremely rare.The anterior compartment of the leg is most frequently involved and appears to be especially vulnerable to developing this complication.Conservative management should be considered in asymptomatic patients but spontaneous soft tissue breakdown with sinus formation may develop and prolonged surveillance is advised.We report two similar cases of calcific myonecrosis of the anterior compartment of the lower leg that developed decades following snakebite.Only two reports of calcific myonecrosis following snakebites have been reported in the English literature and these cases are almost identical to the cases presented here.Yuenyongviwat et al. reported a case of a 66-year-old Thai woman who presented with calcific myonecrosis 52 years after being bitten by a Malayan pit viper (Calloselasma rhodostoma). 18he anterior compartment of the leg was affected and after a four-year period of conservative management, soft tissue breakdown necessitated surgical intervention in the form of mass resection and primary closure with vacuum drainage.Chun et al. also reported a case of calcific myonecrosis following a snakebite.Their case presented 44 years after being bitten, again involved the anterior compartment of the leg and was treated by mass resection. 19lthough neither of our patients could recall the species of snake, a member of the Viperidae family was probably involved.Three viper species are frequently encountered in KwaZulu-Natal, including the puff adder (Bitis arietans), berg adder (Bitis atropos) and night adder (Causus rhombeatus). 15he puff adder specifically, is one of the most common venomous snakes in South Africa and is responsible for more fatal bites than any other snake.If not fatal, puff adder bites frequently result in extensive necrosis that may require amputation of the affected limb. 20 bite from one of these snakes is consistent with previous reports of compartment syndrome 7,13,14,21 and calcific myonecrosis 18,19 following viper bites.Interestingly, venom from the saw-scaled viper (which contains ecarin that activates prothrombin) has also been associated with renal cortical necrosis followed by calcification. 16cute anterior compartment syndrome involves the isolated anterior compartment of the lower leg and usually follows trauma. 22ood et al. reported that approximately 9% of patients with rapid progressive swelling (RPS) after serious snakebites develop compartment syndrome. 23n the acute setting, management involves release of this compartment through a fasciotomy.Compartment syndrome as a result of snakebite frequently involves the anterior compartment in isolation and may be the result of envenomation of this compartment and the specific anatomical characteristics of the anterior compartment of the lower leg.The sequelae of untreated compartment syndrome include rhabdomyolysis, permanent nerve damage, contracture and loss of function, infection and even amputation.Calcific myonecrosis is believed to be a rare complication of untreated compartment syndrome and follows several years to decades after the trauma.

Key words
Conservative management of calcific myonecrosis is advised in asymptomatic patients.5][26][27] A conservative approach does not, however, preclude infective complications.
Affected patients may present with soft tissue breakdown as the mass enlarges and de novo infection has also been reported. 5Spontaneous soft tissue breakdown with sinus formation was seen in one of our cases and in the case reported by Yuenyongviwat et al. 18 Patients with calcific myonecrosis should be followed closely so that early intervention can be initiated once soft tissue breakdown occurs.
The theory that calcific myonecrosis develops after compartment syndrome suggests that a treatable cause for this complication exists.Patients who present with snakebites to the lower limb should be carefully evaluated for compartment syndrome and the appropriate treatment instituted.

Conclusion
Calcific myonecrosis is a rare complication following snakebites.The anterior compartment of the leg is most frequently involved and appears especially vulnerable to developing this complication.Conservative management should be considered in asymptomatic patients but spontaneous soft tissue breakdown with sinus formation may develop, and prolonged surveillance is advised.