H-ABC Presenting as Asymmetric Dystonia in a Patient with Sturge–Weber Syndrome

Hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC, MIM612438) is a rare hereditary disease caused by a mutation in the TUBB4A gene.[1] Patients with H-ABC present extrapyramidal movement abnormalities (rigidity, choreoathetosis, and dystonia) that correlate with the MRI findings (diffuse hypomyelination/atrophy of the neostriatum and cerebellum).[2] [3]

Our patient was initially diagnosed with Sturge–Weber Syndrome (SWS, MIM185300). He presented with a right facial hemangioma noticed at birth and left hemiparesis and focal seizures at 3 and 7 months, respectively; a CT scan revealed a leptomeningeal angiomatosis ([Fig. 1 A]–[B]).

Fig. 1 (A and B) Axial CT scan shows a posterior right serpentine leptomeningeal enhancement. (C) Axial T2 MRI shows generalized hypomyelination and atrophy of the basal ganglia. (D) Sagital T1 MRI shows a marked cerebellum atrophy. CT, computed tomography; MRI, magnetic resonance imaging.

At the age of 7 years, the patient presented dystonia that was more evident in the left side of the body ([Video 1], Sequence 1). By the age of 11 years, his motor deficit worsened progressively making him wheel-chair dependent; his neurological examination revealed asymmetric generalized dystonia and worsening of spasticity on the right side of the body, which was initially minimally affected ([Video 1], Sequence 2). A brain MRI showed diffuse hypomyelination and cerebellar and basal ganglia atrophy ([Fig. 1C]–[D]), a genetic test showed a de novo heterozygous mutation in the TUBB4A gene (c.745G > A, p.Asp249Asn).

Video 1 A video accompanying this article is available in the supporting information. Sequence 1 At 7 years, the patient presented a marked spastic, dystonic left hemiparesis. The right upper limb is less affected, looking more relaxed, and able to reach the object more easily. Sequence 2 The right side of the body is more affected. The left upper limb has more stable movements and is able to grasp a pen on the first attempt; on the contrary, the right upper limb has more abnormal movements, including tremor, dysmetria, and can only grasp the pen after several attempts. Online content including video sequences viewable at: www.thieme-connect.com/ejournals/html/doi/10.1055/s-0037-1606857.

The TUBB4A gene has a variable expression and SWS has been associated with early focal accelerated myelination; both factors could have affected the clinical presentation.[4] [5]

Financial Disclosure

Dr Mauricio R. Delgado and Dr Zurisadai Gonzalez-Castillo declare no financial disclosures.

• References

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