O'Sullivan-McLeod syndrome
Findings
No curated finding names O'Sullivan-McLeod syndrome yet. Everything below is reference data from Mondo, HPO and GenCC, not evidence about what affects it.
Definition
O'Sullivan McLeod syndrome is a benign lower motor neuron disorder and a rare variant of monomelic amyotrophy (MA), characterized by an initial unilateral weakness in the intrinsic hand muscles that eventually spreads to the opposite limb (with an asymmetrical distribution) and that has a very slow progression of muscular atrophy over a 20 year period.
Definition from the Mondo Disease Ontology (MONDO:0020559), read 2026-09-29. CC BY 4.0.
Features
12 features
What the disease is reported to present with, and how often among people who have it — never how often a feature means the disease. HPO, annotations 2026-09-02.
- EMG abnormalityHPOHP:0003457
- Very frequent (80% to 99% of cases)
- Hand muscle weaknessHPOHP:0030237
- Very frequent (80% to 99% of cases)
- Intrinsic hand muscle atrophyHPOHP:0008954
- Very frequent (80% to 99% of cases)
- Upper limb muscle weaknessHPOHP:0003484
- Very frequent (80% to 99% of cases)
- Atrophy of the spinal cordHPOHP:0006827
- Frequent (30% to 79% of cases)
- Cold paresisHPOHP:0031372
- Frequent (30% to 79% of cases)
- EMG: chronic denervation signs
Reported absent (2)
- Hyperintensity of MRI T2 signal of the spinal cordHPOHP:0040272
- Somatic sensory dysfunctionHPOHP:0003474
Where it sits
- A kind of