Myofibrillar myopathy type 8 mimicking a Limb-Girdle Muscle Dystrophy: the first Tunisian case report

Myofibrillar myopathy (MFM) type 8, caused by PYROXD1 gene variants, has recently been identified and has been rarely reported to date.

Our aim was to report the first case of MFM type 8 from Tunisia with delayed diagnosis due to a non-specific clinical presentation.

A 36-year-old North-African male presented to our neurology department with a 15-year history of progressive muscle weakness leading to difficulty in walking and standing without dysphagia or facial weakness. His family history was unremarkable, with no similar cases reported. His medical history was insignificant, with no previous or current medication.

Neurological examination noted symmetrical proximal motor deficit in all four limbs with calf pseudohypertrophy and hyporeflexia in lower limbs. Proximal muscular dystrophy was suspected. Normal levels of blood creatine kinase (CK) and lactate dehydrogenase were noted, and the immunological work-up was negative. A muscle biopsy of the anterior tibialis was performed, revealing a histopathological pattern consistent with proximal muscle dystrophy suggestive of Limb-Girdle Muscle Dystrophy (LGMD).

Whole exome sequencing (WES) was performed, revealing a homozygous variant NM_024854.3: c.464A > G on the PYROXD1 gene. The diagnosis of MFM type 8 was retained, and physical therapy was prescribed. At 2-year follow-up, a slight worsening of motor deficit was observed, but his modified Rankin's scale remained stable at 3.

We reported the first Tunisian case of MFM type 8 associated with a well-known pathogenic variant in the PYROXD1 gene. This case mimics LGMD with a moderate deficit and slow progression. MFM type 8 can present with different phenotypes, making the diagnosis difficult.