Question

A patient with HIV receiving antiretroviral therapy including stavudine develops burning pain and numbness in a glove-and-stocking pattern along with absent ankle reflexes. Laboratory tests reveal elevated serum lactate levels. What is the most likely diagnosis?

• A. Stavudine-induced toxic neuropathy
• B. HIV-associated distal sensory polyneuropathy
• C. HIV-associated vacuolar myelopathy
• D. HIV-related inflammatory myopathy

Hint:

Due to the high rates of mitochondrial toxicity (neuropathy, lipoatrophy, lactic acidosis), Stavudine is no longer recommended in modern first-line ART regimens and has been largely replaced by safer NRTIs like Tenofovir and Abacavir.

Answer 1

The Correct Option is A

Concept:
The patient presents with a painful, symmetric, distal sensorimotor peripheral neuropathy (evidenced by the "glove-and-stocking" pattern and absent ankle reflexes).
Because the patient is HIV positive and on antiretroviral therapy (ART), the differential primarily lies between a neuropathy caused by the HIV virus itself versus a toxic neuropathy caused by the medications.
The presence of elevated serum lactate is the critical differentiating diagnostic clue.
Explanation:
• Stavudine (d4T) is an older generation Nucleoside Reverse Transcriptase Inhibitor (NRTI) used in HIV therapy.

• The major class-wide adverse effect of older NRTIs (particularly stavudine and didanosine) is their affinity for inhibiting human DNA polymerase gamma, an enzyme essential for mitochondrial DNA replication.

• This inhibition leads to severe mitochondrial toxicity and dysfunction.

• Clinically, mitochondrial toxicity manifests most prominently in tissues with high energy demands, causing a severe toxic peripheral neuropathy, myopathy, hepatic steatosis, and potentially fatal lactic acidosis.

• The patient's elevated serum lactate level is a direct, systemic biomarker of this underlying mitochondrial dysfunction (due to impaired aerobic respiration and reliance on anaerobic glycolysis).

• This specific biochemical finding strongly confirms that the neuropathy is a toxic drug effect (Option A) rather than HIV-associated distal sensory polyneuropathy (Option B), which is driven by direct viral neurotoxicity and macrophage activation without causing systemic lactic acidosis.

• Option (C), HIV vacuolar myelopathy, is a disease of the spinal cord (similar to B12 deficiency), presenting with spastic paraparesis, hyperreflexia, and sphincter dysfunction, not an isolated distal peripheral neuropathy.

• Option (D), Inflammatory myopathy, would present primarily with proximal muscle weakness and elevated CK, not a prominent sensory neuropathy.
Final answer:
The combination of neuropathy and lactic acidosis in a patient on stavudine points directly to Stavudine-induced toxic neuropathy secondary to mitochondrial toxicity.