The ˦tiology of sub-acute pulmonary infections

Five cases of a subacute pulmonary infection are described in which the clinical and radiological features differ, but in which there is one common feature—viz., the persistent absence of tubercle bacilli in the sputum. It is nevertheless maintained that these may be regarded as manifestations of atypical pulmonary tuberculosis.

These subacute pulmonary affections are discussed in relation to the so-called benign acute pulmonary tuberculosis, to the progressive primary tuberculous complex, and also to disseminated focal pneumonia and other non-tuberculous broncho-pulmonary infections.

Much confusion exists as to the ˦tiology of these infections. Some observers have classified them as non-tuberculous, because of transient radiographic shadows and clinical and radiological evidence of healing by natural resolution. This process, however, may be common to each clinico-radiological group.

Although recent work shows that much has still to be learned about acute, subacute, and chronic inflammatory processes in the lung, and although both clinical and radiological diagnosis have undoubted limitations, it is suggested that the diagnosis of pulmonary tuberculosis is aided in such cases as these by a synthesis of the following data:

• 1.

  A family history of pulmonary tuberculosis.

• 2.

  The occurrence of constitutional symptoms in the presence of pulmonary infiltration.

• 3.

  The comparative absence of catarrhal symptoms, which are as a rule not so prominent in pulmonary tuberculosis.

• 4.

  A relatively lengthy period of resolution.

• 5.

  The relation of pyrexia to physical exertion, prominent in tuberculosis, and the more definite response of the latter to absolute rest.

It must also be recognised that there exists an infiltration of lung tissue which gives rise to radiological shadows almost identical with those of pulmonary tuberculosis, but which are not, apparently, connected with the tubercle bacillus.