Clinical Guidance

Almost all individuals with UDM-TMD of Finnish heritage have the same pathogenic variant (FINmaj) in the last exon 364 (known as Mex6) of TTN. Other European families with single-nucleotide variants in the Mex6 exon of TTN have the common phenotype when compared to the Finnish phenotype. See .

Source: GeneReviews — "Udd Distal Myopathy – Tibial Muscular Dystrophy"

Penetrance

Penetrance is close to 100% at age 65 years.

Source: GeneReviews — "Udd Distal Myopathy – Tibial Muscular Dystrophy"

Diagnostic Criteria

Suggestive Findings

Udd distal myopathy – tibial muscular dystrophy (UDM-TMD) should be suspected in individuals with the following:

• Distal myopathy. Ankle dorsiflexion weakness manifesting in the fourth to seventh decade

• EMG abnormality. Profound myopathic changes in the anterior tibial muscle but preservation of the extensor brevis muscle

• Muscle MRI findings. Selective fatty degeneration of anterior tibial muscles and other anterior compartment muscles of the lower legs

• Serum CK concentration that is normal or slightly elevated

• Muscle biopsy showing progressive dystrophic changes in the tibialis anterior muscle, with rimmed vacuoles at the early stages and end-stage replacement with adipose connective tissue at later stages of the disease

Establishing the Diagnosis

The diagnosis of UDM-TMD i...

Source: GeneReviews — "Udd Distal Myopathy – Tibial Muscular Dystrophy"

Differential Diagnosis

Genes and disorders in the differential diagnosis of Udd distal myopathy – tibial muscular dystrophy (UDM-TMD) are listed in . Table 4. Genes of Interest in the Differential Diagnosis of UDM-TMD

Management Guidelines

Evaluations Following Initial Diagnosis To establish the extent of disease and needs in an individual diagnosed with Udd distal myopathy – tibial muscular dystrophy (UDM-TMD), the evaluations summarized (if not performed as part of the evaluation that led to the diagnosis) are recommended. Table 5. Recommended Evaluations Following Initial Diagnosis in Individuals with UDM-TMD

Source: GeneReviews — "Udd Distal Myopathy – Tibial Muscular Dystrophy"

Clinical Guidance

Heavy muscle force training of weak muscles should be avoided.

Source: GeneReviews — "Udd Distal Myopathy – Tibial Muscular Dystrophy"

Therapies Under Investigation

Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for access to information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.

Source: GeneReviews — "Udd Distal Myopathy – Tibial Muscular Dystrophy"

Surveillance Guidelines

Table 7.

Recommended Surveillance for Individuals with UDM-TMD

System/Concern | Evaluation | Frequency

Neuromuscular

| Evaluate disease progression need for rehabilitation orthotic treatment. | Every 1-4 yrs

Source: GeneReviews — "Udd Distal Myopathy – Tibial Muscular Dystrophy"