Sarcoglycanopathies: a clinico-pathological study

Limb girdle muscular dystrophy (LGMD) is a heterogeneous group of disorders characterized by limb girdle weakness. There are no clear clinical features that distinguish various types of LGMD.

We studied 26 patients with chronic progressive weakness in limb girdle distribution without early facial involvement with muscle biopsies suggestive of dystrophy/myopathy and positive for dystrophin antibodies. Immunohistochemistry studies of muscle biopsies were done on all patients to classify different types of sarcoglycanopathies.

The mean age of presentation was in the third decade. There were 14 male and 12 female patients. The common pattern of inheritance was autosomal recessive, seen in 53.8%. The more frequent type of LGMD was sarcoglycanopathy (SGP) (53.8%). Amongst the SGPs, alpha-SGP (26.9%) was the most common followed by beta-SGP (15.3%), gamma-SGP (3.8%) and delta-SGP (7.6%). Calf hypertrophy was noted in 53.5% of LGMD and 57.1% of SGPs, extensor digitorum brevis hypertrophy in 42% of LGMD and 35.7% of SGPs, winging of scapula in 39.2% of the LGMD group and 35.7% of the SGPs, valley sign in 28.5% of the LGMD group and 21.4% of the SGPs. Hip abductor sign was positive in 71.4% of LGMD and 64.2% of SGPs. Differential weakness of knee flexors was more common in SGP (57.1%). The mean creatine phosphokinase (CK) value was 2519IU/L and was elevated in 92.8% patients. Muscle biopsy showed a dystrophic pattern in 75% of LGMD and a myopathic pattern in the remaining. Symptomatic cardiac involvement was seen in one patient. ECG changes were seen in 44% of LGMD patients and 50% of the SGP. The common changes noted were T wave inversion in V1, V2 (16%), left ventricular hypertrophy LVH (12%) and right bundle branch block (RBBB) in 12% of the LGMD group.

Sarcoglycanopathy is a more frequent form of LGMD whereas alpha type is the most common among the SGP. The four types of SGP do not differ in the pattern of muscle involvement. A relatively earlier onset, selective weakness of knee flexors and a very high CK may help differentiate SGP from other forms of LGMD. Immunohistochemistry is very useful in classifying the different types of LGMD prior to genetic analysis.