Disseminated histoplasmosis

Disseminated histoplasmosis, also known as progressive disseminated histoplasmosis, is a severe form of histoplasmosis infection typically seen in immunosuppressed patients, especially in the setting of HIV infection. It results from haematogeneous dissemination of the infection, involving multiple organs and systems and associating a high mortality¹.

Terminology

Although it is sometimes referred to as extrapulmonary histoplasmosis, lung involvement is one of the commonest manifestations of this condition².

Epidemiology

Dissemination of the disease is fairly uncommon and may occur in 1 in 2000 acute infections³.

Risk factors

• HIV infection, especially with less than 150 cells/μL CD4^1,4

• Immunosuppressive medications⁴

• Biologic agents (infliximab, etanercept)³

• Immune disorders (idiopathic CD4 lymphocytopenia, Job's syndrome, common variable immunodeficiency)⁴

• Extremes of ages⁴

Clinical presentation

Clinical presentation includes systemic symptoms such as fever, weight loss and fatigue and local systems depending on the organs involved, with frequent progressive shortness of breath and diarrhoea^1,3.

Physical examination may reveal hepatoesplenomegaly, lymphadenopathy and skin and oral lesions¹.

Location

• Lungs: parenchymal disease².

• Gastrointestinal: any site of the digestive tube can be involved, with potential bleeding or perforation^1,4.

• Liver and spleen: haemophagocytic lymphohistiocytosis with macrophage activation syndrome¹.

• Kidneys: granulomatous nephritis¹.

• Adrenal glands: adrenal insuficciency^1,3.

• Central nervous system: meningeal, brain or spinal cord lesions¹.

• Skin¹

Radiographic features

Although multiple organs and systems can be affected, only pulmonary and gastrointestinal manifestations have been completely described.

Pulmonary

Chest radiographs show pulmonary abnormalities in about 50% of the patients². Diffuse multiple small nodules are the most common pattern, even though linear and irregular opacities or segmental, lobar or diffuse air-space opacities can also be observed^2,5.

CT demonstrates diffuse miliary nodules measuring 1-3 mm³. Pleural effusions and thoracic lymphadenopathy are uncommon^2,3. Calcified lymph nodes or granulomas are described in about one third of patients, indicating previous contact with the microorganism².

Gastrointestinal

Others