Association between myotonic dystrophy and primary hyperparathyroidism

Musculoskeletal manifestations of primary hyperparathyroidism

Primary hyperparathyroidism (PHPT) can be associated with a variety of musculoskeletal complaints, which occasionally can be the leading or presenting manifestation. In this paper, we describe the musculoskeletal manifestations observed in patients with primary hyperparathyroidism. Medical record reviews of a select population of 74 patients with primary hyperparathyroidism are seen in a rheumatology practice. Bone manifestations included back pain in 11 patients (15.2 %), generalized bone pain in 7 patients (9.7 %), rib cage/chest pain in 6 (8.3 %), pseudoclubbing in 3, and a giant cell tumor of the mandible in 2 (2.3 %) patients. Articular manifestations such as chondrocalcinosis with or without apatite deposition disease were seen in 13 (17.7 %), arthralgias in 11 (15.2 %), and non-specific synovitis in 7 (9.7 %). Muscle weakness was observed in six patients (8.3 %) and myalgias in three (4.6 %). Less common manifestations such as Achilles tendon rupture, Jaccoud-like arthropathy, sacral insufficiency fracture, arthritis associated with fever of unknown origin (FUO), meningitis, cervical cord compression, and persistent headache were observed in single patients. Musculoskeletal findings are still a frequent and important presentation in patients with primary hyperparathyroidism seen in rheumatology practice. Some of these manifestations can be quite unusual and may represent diagnostic dilemmas to the practicing rheumatologist and/or endocrinologist.

Primary Hyperparathyroidism and Hyperthyroidism in a Patient with Myotonic Dystrophy: A Case Report and Review of the Literature

Various endocrine manifestations are commonly described in myotonic dystrophy (MD), including primary hypogonadism, diabetes mellitus, and thyroid and parathyroid dysfunction. We describe a 46-year-old woman with a family history of MD with her son. She was diagnosed with cardiac arrhythmia and required the implantation of a pacemaker. She was noted to have a bilateral cataract. She complained of muscle weakness, diffuse myalgia, and palpitation. The electromyography (EMG) showed myotonic discharges. Laboratory tests showed high serum calcium 2.83 mmol/L, serum phosphate 1.2 mmol/L, parathormone 362.5 pg/mL, thyroid stimulating hormone TSH 0.02 mIU/L (normal range: 0.34–5.6 mIU/L), FT4 21.17 ng/mL, and negative anti-thyroperoxidase antibodies. Cervical ultrasound revealed a multinodular goiter. The 99mTc-MIBI scintigraphy localized a lower right parathyroid adenoma. The clinical data, the family history of MD, EMG data, and endocrine disturbances were strongly suggestive of MD associated with hyperthyroidism and primary hyperparathyroidism.

Hypothesis: neoplasms in myotonic dystrophy

Tumorigenesis is a multi-step process due to an accumulation of genetic mutations in multiple genes in diverse pathways which ultimately lead to loss of control over cell growth. It is well known that inheritance of rare germline mutations in genes involved in tumorigenesis pathways confer high lifetime risk of neoplasia in affected individuals. Furthermore, a substantial number of multiple malformation syndromes include cancer susceptibility in their phenotype. Studies of the mechanisms underlying these inherited syndromes have added to the understanding of both normal development and the pathophysiology of carcinogenesis. Myotonic dystrophy (DM) represents a group of autosomal dominant, multisystemic diseases that share the clinical features of myotonia, muscle weakness, and early-onset cataracts. Myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2) result from unstable nucleotide repeat expansions in their respective genes. There have been multiple reports of tumors in individuals with DM, most commonly benign calcifying cutaneous tumors known as pilomatricomas. We provide a summary of the tumors reported in DM and a hypothesis for a possible mechanism of tumorigenesis. We hope to stimulate further study into the potential role of DM genes in tumorigenesis, and help define DM pathogenesis, and facilitate developing novel treatment modalities.

A 10-year study of mortality in a cohort of patients with myotonic dystrophy

OBJECTIVE

To determine the age and causes of death as well as the predictors of survival in patients with myotonic dystrophy (DM).

METHODS

In a longitudinal study, a cohort of 367 patients with definite DM was followed for 10 years.

RESULTS

During the 10-year period, 75 of the 367 DM patients (20%) died. The mean age at death (53.2 years, range 24 to 81) was similar for men and women. Among these 75 patients, 32 (43%) died of a respiratory problem, 15 (20%) of cardiovascular disease, 8 (11%) of a neoplasia, and 8 (11%) died suddenly. The ratio of observed to expected deaths was significantly increased to 56.6 (95% confidence interval [CI] 38.7 to 78.0) for respiratory diseases, 4.9 (95% CI 2.7 to 7.7) for cardiovascular diseases, and 2.5 (95% CI 1.1 to 4.6) for neoplasms. The mean age at death was 44.7 years for the childhood phenotype of DM, 47.8 years for the early-adult, 55.4 years for the adult, and 63.5 years for the mild phenotype (F = 4.8, p = 0.005). The age-adjusted risk of dying was 3.9 (95% CI 1.3 to 11.0) times greater for a patient with a distal weakness and 5.6 (95% CI 2.2 to 14.4) times greater for a patient with proximal weakness as compared with a person without limb weakness.

CONCLUSIONS

Life expectancy is greatly reduced in DM patients, particularly in those with early onset of the disease and proximal muscular involvement. The high mortality reflects an increase in death rates from respiratory diseases, cardiovascular diseases, neoplasms, and sudden deaths presumably from cardiac arrhythmias.