C. Blood dyscrasias, as haemophilia, anaemias and scurvy.
D. Toxic, as lead poisoning.
The diseases of more peculiar importance for the tropics in which joint involvement must be considered in the diagnosis are the following:
Malta Fever.—This infection offers a good example of a disease in which joint symptomatology is of diagnostic and therapeutic importance. A prolonged typhoid-like course with sudden and painful swelling of various joints, hip, shoulder, ankle or costo-vertebral articulations, if occurring in the endemic area of Malta fever, would at once make one suspect this disease. Typhoid does not give painful joints, dengue is not accompanied by joint swelling, while gonorrhoeal polyarthritis will be accompanied by other evidence of gonorrhoeal infection.
The neuralgias, sciaticas and painful joints, together with the sweats which exhaust the sufferer from Malta fever, often tempt both patient and physician to resort to narcotics. Acute or subacute effusion into one or more joints is present in at least 40 per cent of cases of Malta fever according to Rogers. The Malta fever joint is not red, which fact, taken with its evanescent character, differentiates it from the arthritis of acute rheumatic fever.
Dengue.—Sporadic dengue is difficult to diagnose. In an epidemic the characteristic pains referable to tendinous insertions about joints are present in at least 50 per cent of cases and is of great diagnostic value. There is no swelling of the joints although the turgescence of the skin over them may give the impression of an arthritis. The intensity of pain varies from a feeling of muscular soreness to excruciating pain when muscles or joints are actively moved. Passive movement is not usually painful. In addition to the rachialgia, bone and joint pains, some writers have described swelling of the joints. This in my experience is unusual. Joint pains are so characteristic that they distinguish dengue from all other eruptive fevers.
Joint pains during convalescence may produce stiffness and crippling continuing for many weeks after the cessation of fever.
Relapsing Fever.—Bone, muscle and joint pains are practically always present in this disease. In addition rachialgia and headache are prominent symptoms and the aching gnawing pains in loins or nape of neck may make one think of beginning smallpox, dengue or yellow fever. There is no swelling of the joints in relapsing fever. As in dengue the pains in the neighborhood of the joints may be quite persistent.
Yaws.—This disease gives us bone, joint and muscle lesions similar to those of syphilis. From the mother lesion to the tertiary framboesioma the course and symptoms of the two diseases are similar. Thus we may have the flying pains and osteocopic pains of the early days of infection and, as later events, chronic synovitis, frambroesial infiltration of perisynovial membranes, frambroesial infiltration of synovial membranes, chondro-arthritis, epiphysitis and chronic frambroesial periostitis. These pathological processes cause such conditions as we know under the names dactylitis, saber shin, mutilating oro-rhino-palato-pharyngeal ulcerations, Parrot’s nodes and cranio-tabes.