# HTLV-1 Associated Myelopathy

> HTLV-1 associated myelopathy for NEET-PG Medicine: tropical spastic paraparesis, serology in blood and CSF, and differentials of chronic progressive myelopathy.

- Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/htlv-1-associated-myelopathy
- Exam / course: NEET-PG · Subject: Medicine
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-14
- Last updated: 2026-10-14
- Reference basis: Bradley's Neurology in Clinical Practice; Harrison's Principles of Internal Medicine; Davidson's Principles and Practice of Medicine
- How to cite: "HTLV-1 Associated Myelopathy", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/htlv-1-associated-myelopathy

## Direct answer

HTLV-1 associated myelopathy is a slowly progressive spastic paraparesis caused by human T-lymphotropic virus type 1, a retrovirus that also causes adult T-cell leukaemia. It presents with stiff legs, exaggerated reflexes, extensor plantars and urinary urgency, and diagnosis rests on HTLV-1 antibodies in serum and cerebrospinal fluid. Other causes of chronic myelopathy must be excluded before the label is applied.

## What you must remember

- **Virus:** HTLV-1, a retrovirus that infects CD4 T lymphocytes and also causes adult T-cell leukaemia and lymphoma, uveitis and infective dermatitis in children.
- **Transmission:** sexual contact, breast milk, transfusion of infected blood and shared needles, with vertical spread from mother to child.
- **Synonym:** tropical spastic paraparesis, the term used in endemic regions for the same myelopathy.
- **Clinical picture:** insidious, slowly progressive weakness and stiffness of the legs, hyperreflexia, extensor plantar responses and urinary urgency, with mild sensory symptoms.
- **Serology:** ELISA for HTLV-1 antibodies, confirmed by Western blot or PCR, with proviral load supporting the diagnosis.
- **CSF:** mild lymphocytic pleocytosis and raised protein, with intrathecal HTLV-1 antibodies supporting the diagnosis.
- **MRI:** thoracic cord atrophy is commonly seen, though the scan can be normal early, and its main role is excluding a compressive lesion.
- **Treatment:** no antiviral therapy cures the myelopathy, so management relies on physiotherapy, antispasticity drugs such as baclofen or tizanidine, and bladder care.

## Working through chronic progressive myelopathy

HTLV-1 myelopathy is a diagnosis of exclusion, so a short differential guides the work-up. Each alternative has a clue at the bedside and a test that separates it from the others.

| Condition | Key clue | Discriminating test |
|---|---|---|
| HTLV-1 myelopathy | Slow spastic paraparesis, thoracic involvement | HTLV-1 antibodies in serum and CSF |
| Cervical spondylotic myelopathy | Hand clumsiness, neck pain, upper limb signs | MRI of the cervical spine |
| Vitamin B12 deficiency | Posterior column loss, macrocytosis | Serum B12 and methylmalonic acid |
| Lathyrism | Spastic paraparesis after khesari dal (Lathyrus sativus) | Careful dietary history |

A positive HTLV-1 serology alone does not prove causation, because many carriers have no neurological disease. The clinical picture and the exclusion of the other causes in the table are what confirm the diagnosis.

Worked example: a 48-year-old woman from an endemic area has two years of slowly worsening stiff legs, brisk knee jerks and bladder urgency. Serum HTLV-1 antibodies are positive, and CSF shows intrathecal antibodies with a normal MRI apart from mild thoracic atrophy. Neither B12 deficiency nor a compressive lesion is found, so the diagnosis is HTLV-1 associated myelopathy.

## Where the examiner tests the myelopathy

Questions often describe a slowly progressive spastic gait in a patient from an endemic area and ask for the cause or the next test.

- **Trap:** Accepting a positive HTLV-1 serology as proof of myelopathy. — **Correct:** Many carriers are asymptomatic, so the clinical picture and the exclusion of other causes must confirm the diagnosis.
- **Trap:** Labelling every spastic paraparesis in India as HTLV-1 myelopathy. — **Correct:** Lathyrism, vitamin B12 deficiency and compressive lesions must be excluded first, and a dietary history is essential.
- **Trap:** Treating HTLV-1 with antiretrovirals as a cure. — **Correct:** No antiviral therapy cures the myelopathy, and management is symptomatic, including bladder care and physiotherapy.
- **Trap:** Ignoring the leukaemia risk in a carrier. — **Correct:** Carriers are at lifelong risk of adult T-cell leukaemia, so counselling and follow-up are part of care.

## Frequently asked questions

### Which virus causes HTLV-1 associated myelopathy?

HTLV-1 associated myelopathy is caused by human T-lymphotropic virus type 1, a retrovirus that infects CD4 T lymphocytes. The same virus causes adult T-cell leukaemia and lymphoma. Diagnosis uses HTLV-1 antibodies in serum, confirmed by Western blot or PCR.

### What is the clinical picture of tropical spastic paraparesis?

Tropical spastic paraparesis presents with slowly progressive stiffness and weakness of the legs, exaggerated reflexes and extensor plantar responses. Bladder urgency and mild sensory symptoms often accompany it. Tropical spastic paraparesis is the same condition as HTLV-1 associated myelopathy, the term used in endemic regions.

### Which MRI finding is typical in HTLV-1 associated myelopathy?

Thoracic spinal cord atrophy is commonly seen on MRI in HTLV-1 associated myelopathy, although the scan can be normal early in the disease. MRI is used mainly to exclude a compressive lesion, such as a spinal tumour or cervical spondylosis. The imaging finding alone does not establish the diagnosis.

### How does HTLV-1 associated myelopathy differ from lathyrism?

HTLV-1 associated myelopathy is a viral, slowly progressive disease, whereas lathyrism is a neurotoxic spastic paraparesis caused by eating Lathyrus sativus. Lathyrism is linked to a diet rich in khesari dal, so a careful dietary history separates the two. Both present with lower limb spasticity, which is why the history is decisive.