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Q1: What is the differential diagnosis of this clinical presentation and radiological picture?
A chronic infection of skull and scalp was diagnosed and pyogenic, tuberculous, and fungal osteomyelitis were considered in the differential diagnosis.
Q2: How should this patient be managed?
Chronic non-healing scalp infection needs thorough debridement of the wound and excision of osteomyelitic bone till healthy bone margins are reached. Appropriate antibiotic treatment, based on microbiological tests, is usually needed for weeks to months.
Our patient underwent drainage of the subcutaneous pus and debridement of the wound. The bone was not excised as a very extensive area of bone seemed to be involved on the x ray films, and the outer table looked intact at surgery. Multiple pockets of pus and granulation tissue were seen in the subcutaneous plane. Pus smear showed Gram positive, branching filaments. There was a heavy growth of aerobic actinomycetae on Lowenstien-Jensen medium, and on Sabouraud dextrose agar, suggestive of nocardia, which was sensitive to co-trimoxazole and penicillin. There was no growth of mycobacteria or other pathogens. The histopathological examination revealed dense infiltrate of vascular granulation tissue and exudate (with no granulomata, or caseation), suggestive of chronic non-specific inflammation.
Q3: What is the optimal treatment of this condition?
The natural history of primary cutaneous nocardial disease is not known. As cure with surgical debridement alone occurs in only one third of cases, drug therapy is recommended in all patients.1 The optimal antibiotic therapy for nocardiosis has not been established. Trimethoprim-sulfamethoxazole acts synergistically against most strains of nocardia (in vitro),2 and so also minocyclin, amikacin, and imipenem.3 Our patient was thus treated with sulphonamides and amikacin along with surgical debridement. The duration of therapy for nocardiosis varies from three months to one year with the type and extent of the disease.1 Considering the chronicity of the disease and extensive bony involvement in our patient, a prolonged course of therapy (co-trimoxazole for one year) was advised.
Nocardia are soil saprophytes that usually cause respiratory infection in immunocompromised hosts, and extrapulmonary lesions may follow metastatic spread from the pulmonary focus. However solitary, extrapulmonary, lesions, involving skin and subcutaneous tissue, occur in significant number of immunocompetent patients after direct inoculation. Inprimary cutaneous nocardiosis a history of local trauma, with soil contamination, is frequently present and commonly occurs in the extremities in adults (for example gardening accident victims).1
Two forms of nocardial skin infection have been described4—the acute lymphangitic form and chronic actinomyecetoma—with formation of nocardia grains (aggregates of filaments). The main sign of infection is the development of firm subcutaneous swelling, but later draining sinus tracts form, which discharge serosanguineous material and grains of nocardia onto the skin surface; bone involvement occurs by extension.4 The characteristic histopathological response to nocardial infection is the production of chronic inflammatory exudate without extensive fibrosis, caseation, or granuloma.
Primary cutaneous nocardiosis can occur in an immunocompetent host.
In a case of chronic infection of bone and subcutaneous tissue, with multiple sinuses, nocardiosis should be considered in the differential diagnosis.
Chronic nocardial skin infection can manifest, after a long period of incubation, after primary inoculation.
In reported cases of primary cutaneous nocardiosis after inoculation, there is seldom any evidence of impaired immune response of the host5; and local inflammation and lymphadenopathy usually follows. Initial failure of these mechanisms to eliminate all organisms, and confinement to a local site, may subsequently lead to the development of actinomyecetoma.4 The factors affecting this change from acute to chronic phase are unclear; but it is proposed that the host's immune response as well as the ability of the organism to lose their cell wall structure,5 may affect this transformation. In our case, the long incubation period after inoculation, and subsequent chronicity of the disease, may be due to the transiently altered immune status.
In conclusion, when a patient presents with chronic, non-healing sinuses of the scalp, nocardiosis must be considered in the differential diagnosis, especially if there has been a history of trauma even in the remote past and specific cultures should be asked for.
Actinomyecetoma form of primary cutaneous nocardiosis of scalp with involvement of skull bones.
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