Secondary syphilis in HIV infection - a diagnostic dilemma

Co-existence of syphilis and HIV infection is being increasingly seen in clinical practice. Both are supposed to have influence on each other with altered immune response to many infections. Several unusual manifestations of syphilis may be seen in concurrent HIV infection like high incidence of HIV seropositivity, increased severity of clinical manifestations, rapid progression of syphilis, seronegativity, relapse inspite of adequate treatment and failure of benzathine penicillin.[1] We encountered one such patient manifesting with skin rash suggestive of secondary syphilis. Blood test was found to be non reactor, thereby producing diagnostic difficulties.

Case Report

A 35-year-old soldier was admitted with history of generalised skin rash of about four weeks duration. The rash was asymptomatic in nature and was not accompanied by fever or any constitutional symptoms, joint pain etc. Patient denied any history of drug intake or extramarital sexual contact prior to the onset of rash. He did not give any history of genital sore in the past.

Examination showed an averagely built and nourished individual with normal vital parameters. Systemic examination did not reveal any abnormality.

Dermatological examination showed bilaterally symmetrical, generalised, maculopapular rash, not involving palms and soles. The lesions showed erythema and ill defined borders. Some of the lesions showed Buschke-Ollendorff sign positivity. There were no evidences of any hair loss, mucous membrane lesions, arthralgia or periostitis. There was no lymphadenopathy.

A clinical diagnosis of secondary syphilis was made and the patient was investigated. His routine blood tests and urinalysis were normal. Blood for VDRL was reported to be non reactor. Suspecting prozone phenomenon, blood was tested again in dilution and was still non reactor. HIV test done by ELISA at this stage was found to be positive. A skin biopsy showed no evidence of endarteritis obliterans but perivascular infiltration of lymphocytes and plasma cell could be seen. Based on clinical findings and presence of plasma cells in the biopsy specimen, it was decided to give a therapeutic trial with 2.4 mega units of benzathine penicillin. Within eight hours, he developed constitutional symptoms and skin rash became prominent, thereby suggesting Jarish-Herxheimer reaction. The constitutional symptoms subsided within 24 hours and skin rash gradually faded after seven days. Blood VDRL test done after one week of treatment showed positivity 1:32 dilution, came down to 1:16 in another week and was negative after three months. A CSF examination was found to be normal with VDRL negativity.

Discussion

Our patient reported with skin lesions suggestive of secondary syphilis. However, absence of any constitutional symptoms, or associated mucous membrane changes made diagnosis slightly difficult. This was further compounded by sero-negativity to VDRL test done even in dilutions.

At this time, HIV report was available and was found to be positive. Suspecting HIV infection to be the reason behind sero-modification, skin biopsy was performed. However no classical syphilitic endarteritis obliterans could be seen but perivascular infiltration with lymphocytes and plasma cells was evident.

Thus on the basis of clinical pictures and plasma cells in the biopsy specimen, we decided to give the patient therapeutic trial with benzathine penicillin. He promptly showed Jarish-Herxheimer confirming our suspicions. Subsequent clinical response and VDRL reactivity confirmed the diagnosis. HIV and syphilis are known to coexist and several areas of interaction are suspected.[2] Serological response can vary from normal response to exaggerated response to total lack of immune response.[3] Because of wide range of clinical presentation and diverse serological picture, a high degree of clinical suspicion is required while tackling such cases.