Importance of biopsies for confirming cause of muscle disease in HIV patients shown by case reports

Two unusual cases of muscle disease in HIV-positive patients are reported in the August edition of Sexually Transmitted Infections. Although the underlying cause of the muscle disorder differed in both patients, there were similarities between the cases, not least that both patients had more or less normal laboratory results, and that the initiation of HAART led to a resolution of the complaint. In addition, in both patients a muscle biopsy was needed to confirm a diagnosis, and the investigators emphasise the importance of performing muscle biopsies on HIV-positive patients with muscle weakness with no or little evidence of laboratory abnormalities.

HIV-positive patients are vulnerable to a number of muscle disorders which can be caused by the direct effects of HIV, infections, or antiretroviral drugs. However, in only 15% of asymptomatic HIV-positive patients are creatine phosphokinase (CPK) levels, a biochemical marker of muscle disease, abnormal and a biopsy is needed to confirm a diagnosis.

Investigators from London report two cases of HIV-positive patients reporting muscle weakness but with no or very minor abnormalities in their CPK levels and normal electromyograph readings.

The first case involved a 50 year old African woman who had been diagnosed with HIV three months previously. She complained of a muscle weakness in the legs lasting for four weeks. Her CD4 cell count was 340 cells/mm³, and tests for infections proved negative. A test revealed that her CPK levels were slightly elevated, an x-ray of her thigh muscles was normal and an electromyography did not provide a diagnosis.

A sample of tissue was obtained from the left leg and showed muscle inflammation with infiltration of muscle fibres by CD8 cells. A HAART regimen containing 3TC, ddI and Kaletra was started and the woman rapidly regained mobility, and after three months on HAART her CD4 cell count was 310 cells/mm³, her viral load was undetectable and her CPK levels were normal.

The second case involved a 51 year old gay man who had had diagnosed HIV infection for ten years. He told doctors that he had a two-year history of leg weakness which was particularly severe when walking or cycling up hills. The man was not taking HAART, but had been taking ddI and ritonavir for six years. The patient had a CD4 cell count of 220 cells/mm³ and a viral load of 200 copies/ml.

There was no family history of neurological disease but the man’s thigh muscles were wasted. Investigations, including a CPK test proved to be normal, and an electromyograph found no evidence of muscle disease.

A muscle biopsy showed evidence of mitochondrial toxicity. In the light of this finding, therapy with ddI and ritonavir was stopped and the patient started a HAART regimen consisting of abacavir, 3TC and nelfinavir. Two months later the man had no symptoms and an undetectable viral load.

“These two cases add to the differential diagnosis of causes of muscle disease in this patient population,” write the investigators, who add, “they also serve to underscore the importance of muscle biopsy in identifying the underlying pathology in HIV infected patients with non-specific symptoms of muscle weakness, normal or minor elevations in CPK and normal EMG findings.”