Charcot-Marie-Tooth Neuropathy (CMT)

General description

Affected dogs of the breed Miniature Schnauzer suffer from a mega-oesophagus with frequent regurgitation, as well as breathing difficulties due to laryngeal paralysis. In the Lancashire Heeler breed, CMT is associated with features of amelogenesis imperfecta and subclinical peripheral neuropathy.

Breeds

Lancashire Heeler, Miniature Schnauzer

Charcot-Marie-Tooth Neuropathy (CMT) - Miniature Schnauzer

In the breed Miniature Schnauzer, a variant in the SBF2 gene (also known as MTMR13 gene) has been found to cause Charcot-Marie-Tooth neuropathy (CMT). Affected dogs show regurgitations caused by mega-esophagus and inspiratory dyspnea caused by laryngeal paralysis at a young age (< 2 years). In the previously described cases, affected dogs have been alive more than 3 years following diagnosis which indicates a long survival rate.

Typical pathological findings are variable thickness of the myelin sheath (so-called “tomacula”) around the axons of peripheral nerves and areas of segmental demyelination. The described variant has not been found in other breeds than Miniature Schnauzers.

Charcot-Marie-Tooth Neuropathy (CMT) - Lancashire Heeler

In the breed Lancashire Heeler, a genetic variant of the ITPR3 gene has been found to be associated with CMT. Due to a severe developmental enamel defect, affected dogs show features of amelogenesis imperfecta, including severe yellow to brown discoloration, enamel hypoplasia and abrasion leading to dentin exposure.

The second common symptom of the disease is a subclinical peripheral neuropathy. Therefore, affected dogs show normal locomotion and activity levels, but electrodiagnostic examinations emerge neurogenic changes in muscle, especially in muscles distal to elbow and knee joints, consistent with demyelinating neuropathy.