Balkan Journal of Medical Genetics

MYOTONIC DYSTROPHY-2: UNUSUAL PHENOTYPE DUE TO A SMALL CCTG-EXPANSION
Finsterer J, Stöllberger C, Reining-Festa A, Loewe-Grgurin M, Gencik M
*Corresponding Author: Josef Finsterer, M.D., Ph.D., Krankenanstalt Rudolfstiftung, Messerli Institute, Veterinary University of Vienna, Postfach 20, 1180 Vienna, Austria. Tel. +43-1-71165-92085. Fax. +43-1-4781711. E-mail: fifigs1@yahoo.de
page: 39

CASE REPORT

The patient is a 52-year-old, HIV-negative, Caucasian female, height 162 cm, weight 85 kg, with a history of surgery for vesico-ureteral reflux at ages 10 years (right), 11 years (left) and 13 years (left), diabetes first occurring during gestation at ages 21 and 22 years and requiring insulin since age 25 years, surgery for cutaneous melanoma without requiring radiation or chemotherapy at age 30 years, hyperlipidemia since at least age 31 years and hyperuricemia since age 32 years (Figure 1). At age 32 years, initially isolated and asymptomatic hyper-CKemia, became evident (Figure 1). Since then, hyper-CKemia remained elevated throughout the next 20 years with an undulating course and a maximal value of 2262.0 U/L at age 38 years (Figure 1). At age 38 years, multiple renal cysts and hydronephrosis-I on the left side were first found on abdominal ultrasound and on abdominal computerized tomography (CT) at age 51 years (Figure 2). At age 39 years conization had to be carried out because of recurrent dysplasias papanicolaon staining(PAP) IIID followed by hysterectomy 2 days later. For recurrent thrombocytosis since age 40 years, the patient underwent a bone marrow aspiration at age 42 years, demonstrating moderate increase in megakaryocytes suggesting essential thrombocytosis. During further course, the patient developed bilateral cataracts requiring surgery at ages 41 years and 49 years, respectively, arterial hypertension since age 46 years, heterozygous Factor-V Leiden (FVL) mutation detected at age 46 years, incipient, symmetric, axonal poly-neuropathy on the lower limbs detected upon nerve conduction studies at age 47 years, cholecystolithiasis first detected at age 47 years, multiple ovarial cysts bilaterally first detected at age 51 years, and vitamin-D deficiency since age 52 years. She was smoking cigarettes. An electrocardiogram (ECG) at age 47 years was normal. The family history was positive for hyper-CKemia [mother (300.0 U/L), sister (200.0-300.0 U/L), daughter (up to 300.0 U/L)], muscle weakness (mother, sister), and diabetes (mother). The 27-year-old son had normal CK values. Her current medication includes insulin, toujeo, metformin, candesartan, amlodipine, acetyl-salicylic acid, and B-vitamins. At age 51 years the patient was referred for anginal chest pain and proximal, exercise-induced muscle weakness. Muscle weakness became evident when descending stairs or getting up from the floor. She reported a myotonic reaction when opening the fists. The ECG revealed a left anterior hemiblock, echocardiography and coronary angiography were normal. Clinical neurologic exam exclusively revealed distal sensory disturbances on the lower limbs, and reduced Achilles tendon reflexes. In addition to longterm hyper-CKemia, glutamate-oxalat transaminase (GOT), glutamate pyruvate transaminase (GPT), lactate dehydrogenase (LDH), hyperlipidemia, hyperglycemia, thrombocytosis, and hyperuricemia, blood tests showed reduced serum iron and elevated neutrophil granulocytes. Needle electromyograpny (EMG) of the right deltoid, left dorsal interosseous-I, and right anterior tibial muscles revealed myotonic and pseudomyotonic discharges at each recording site. Needle-EMG of the masseter muscle was normal. Genetic investigations for MD1 revealed CTG-repeat sizes of five and 10 repeats on either allele of the DPMK gene respectively. Myotonic dystrophy type 1 was thus excluded. Investigations for MD2 revealed a normal CCTG-repeat size on one allele of the ZNF9 gene (134 bp, equivalent to 34 repeats) and an abnormal expansion on the second allele. Unfortunately, the exact size of the expansion on the second allele was not provided by the laboratory. Genetic testing of the son revealed a normal CCTG repeat length on both alleles. The daughter is considering undergoing the test. Mother and sister refused to be tested. Investigations were carried out according to the Declaration of Helsinki.

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