David Irvine1 and Mike Leach2
1Department of Haematology, Glasgow Royal Infirmary, 3rd Floor, McEwan Building, Glasgow, G4 0SF.
2Department of Haematology, Stobhill Hosptal, 133 Balornock Rd, Glasgow, G21 3UW
Corresponding Author: Dr M. Leach Email: mike.leach@NorthGlasgow.scot.NHS.uk
SMJ 2007 52(4): 53
Abstract
We describe a 73-year-old gentleman who was referred
to haematology for management of myeloma following the discovery of a small
plasmacytoma of the tonsil and an osteolytic lesion in the head of his left
humerus. Investigation for myeloma
was negative and the lytic lesions were explained by dysbaric osteonecrosis
rather than myelomatous bone involvement. He had worked on the construction of
the Clyde tunnel between 1958 and 1963 and had been subjected to repeat
compression/decompression cycles. He was diagnosed with a solitary
extramedullary plasmacytoma of the nasopharynx, which responded well to local
radiotherapy.
Keywords: Solitary
Extramedullary Plasmacytoma, Dysbaric Osteonecrosis, Multiple Myeloma.
Case Report
A 73-year-old man was referred to the Haematology
department with a presumed diagnosis of Multiple Myeloma following the discovery
of a small plasmacytoma of the tonsil and an osteolytic lesion in the head of
the left humerus. The patient
was entirely asymptomatic with a normal full blood count, calcium level and LDH
as well as normal renal and liver function.
Serum electrophoresis and immunofixation were negative and no Bence-Jones
protein was evident in the urine. Bone
marrow examination was normal. A
skeletal survey (Fig 1A) and CT scan (Fig 1B) confirmed the presence of lytic
areas in the heads of both humeri but no other radiological abnormality.
Fig 1. Skeletal survey (A) demonstrated the
presence of bilateral humoral head lucencies but was otherwise normal. CT scan
(B) further characterised the extent of the bone necrosis.
Figure 1A
Figure 1B
We ascertained from the patient that he had worked on the construction of the River Clyde road tunnels in Glasgow, Scotland between 1958 and 1963. During construction the tunnel workers worked under pressurised conditions of up to 2.4 atmospheres for 8 hours per day. Decompression occurred for up to 1 hour at the end of each shift but workers were often tempted to leave early. However, even strict adherence to the decompression protocol did not appear to eliminate risk completely. He was frequently troubled by severe pains after work and his wife would often massage the affected joints and muscles well into the evening. Despite this, he had to return to his workplace for formal recompression on several occasions. On review, and together with this additional relevant history, the radiological abnormalities of the proximal humeri were reassessed and felt to be entirely consistent with dysbaric osteonecrosis.
Given the absence of a second involved locus, any evidence of bone marrow involvement or a monoclonal paraprotein the patient was diagnosed with a solitary extramedullary plasmacytoma. The plasmacytoma has resolved following local radiotherapy and he remains well on follow up without local or systemic recurrence. The humeral lesions remain asymptomatic.
Discussion
Dysbaric osteonecrosis is a condition, which most often occurs in deep sea divers and tunnel workers who have been exposed to repeated compression/decompression cycles.1, 2 It has also been reported in recreational scuba divers and in Turkish sponge divers.3, 4 It occurs because increased partial pressure of nitrogen (and other gases) while at greater than atmospheric pressures leads to increased levels of nitrogen in tissues and blood. Decompression induces the formation of intravascular nitrogen bubbles, which can result in intramedullary venous stasis, ischaemia, and eventually necrosis of bone. There is a strong association between episodes of decompression sickness, also known as Caisson’s disease and ‘the bends’, and subsequent radiological evidence of osteonecrosis. The humeral and femoral heads (rhizomelic or ball and socket joints) are known to be particularly susceptible. This is because the perfusion and drainage of blood from the femoral or humeral head with a relatively large volume and surface area is solely through the neck. The Medical Research Council Decompression Sickness Panel studied the Clyde tunnel workers between 1958 and 1963.5,6 Two parallel tunnels about 400 feet (121.9m) long were constructed some 21 feet (6.4m) below the river bed. When a tunnel is being constructed under a riverbed, compressed air is required to support the sub strata and prevent water entering. Air locks were positioned at the entrance to each tunnel through which the workers had to pass on entering or leaving. On entering, the pressure was raised rapidly but on leaving had to be reduced slowly. The period of decompression required is proportional to the pressure in the tunnel and the length of exposure. The frequency of decompression sickness was 0.31% in workers exposed to pressures over 18 pounds per square inch (1.22 atmospheres). The Panel investigated 241 men who had worked in pressures of up to 35 pounds per square inch (2.38 atmospheres). Radiological evidence of osteonecrosis was present in 47 men (19%). Virtually all lesions were in the humeri or femora and most were periarticular. No lesions were seen in the pelvis, scapulae, clavicles or ribs. Workers with bone lesions had experienced significantly more decompressions and were more likely to have been treated for ‘the bends’. In the longer term these lesions tend to be painless unless there is collapse or disruption of the articular surface. These lesions may be misinterpreted, as in this case, unless an adequate history is taken. Dysbaric osteonecrosis should be considered in any patient with painless lucencies in humeral or femoral heads particularly if there is a history of occupational exposure to conditions of increased atmospheric pressure.
Solitary extramedullary plasmacytoma (SEP) is a soft tissue infiltration of clonal plasma cells. The majority (>85%) are found in the mucosa of the head and neck (primarily the upper aerodigestive tract). It is a relatively rare condition comprising about 1% of all plasma cell dyscrasias. The main differential diagnoses are multiple myeloma and other lymphoproliferative diseases such as immunoblastic lymphoma. Diagnosis of SEP relies on demonstrating a single extramedullary mass of plasma cells in association with normal bone marrow studies, absent or low levels of monoclonal paraprotein, absence of immune paresis with no evidence of myelomatous bone destruction on skeletal survey. Solitary extramedullary plasmacytomata are highly radiosensitive tumours and the prognosis is generally excellent. The majority of patients will achieve remission with local radiotherapy and few will recur or transform to systemic disease.7
Conclusion
Dysbaric osteonecrosis is an occupational hazard for any workers exposed to repeated compression/decompression cycles. This condition should be considered in any patient with painless lucencies in humeral or femoral heads. It is important that such lesions are not misinterpreted leading to potential erroneous diagnosis of multiple myeloma, as in this case, in a patient with a solitary pharyngeal extramedullary plasmacytoma.
References
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Jones JP, Benkhe AR. Prevention of Dysbaric Osteonecrosis in Compressed-Air Workers. Clinical Orthopaedics and Related Research (1978)130; Jan-Feb, p118-128.
Wilmshurst P, Ross K. Dysbaric osteonecrosis in the shoulder of a sport scuba diver. British Journal of Sports Medicine (1998) 32(4): p344-345.
Toklu AS, Cimit M. Dysbaric osteonecrosis in Turkish sponge divers. Undersea and Hyperbaric Medicine (2001) 28(2); p83-88.
McCallum RI, Walder DN. Bone lesions in compressed air workers. With special reference to men who worked on the Clyde tunnels 1958 to 1963. The Journal of Bone and Joint Surgery (1966) 48B(2); p207-235.
Davidson JK. Radiology in Decompression Sickness: The Clyde Tunnel. Scottish Medical Journal (1964) 9(1): p1-9.
Guidelines
on the diagnosis and management of solitary plasmacytoma of bone and
solitary extramedullary plasmacytoma United Kingdom Myeloma Forum, British
Journal of Haematology (2004), 124, p717–726.