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Abstract

Introduction


Congenital myotonic dystrophy is a rare autosomal dominant disease, which begins to show its symptoms in the intrauterine period and differs significantly from myotonic dystrophy of adults. The major feature differentiating it from the adult type is hypotonia, instead of myotonia. It was first discribed by Vanier in 1960. The diagnosis is quite easy if there is an index case in the family. The surviving babies are usually mentally retarded in later life. We present a family and their latest offspring with myotonic dystrophy, and discuss issues relevant to the disease. Case Report This baby girl was born through vaginal delivery to a non-consanginous 40 year old mother, as her 6th child, after 39 weeks of gestation. Her birthweight was 2150g and her length was 48 cm. The pregnancy of the mother was remarkable for polyhydramnios. On her first physical examination, profound hypotonia, tent-shaped upper lip, bilateral ptosis of the eyelids and retrognathia were noticed (Figure 1). She did not have any findings compatible with arthrogyriposis. Starting immediately after birth, moderate respiratory distress and intercostal retractions were evident. However, arterial blood gases were within acceptable limits and peripheral oxygen saturation as measured by pulse oximeter was in the range of 90-95%. On her chest x-ray, both diaphragms were elevated, decreasing the expansion space of the lungs. However, the aeration of the lungs were satisfactory. (Figure 2). She was given free oxygen by hood and recovered within 2 days, after which she was started on oral feeding. From the 3rd to 6th days, she had moderate feeding difficultly with gastric desiduals, but recovered from the 7th day onwards and on the 12th day of life, she was feeding completely on breast milk by oral route. A cranial ultrasonography was found to be normal. Family history revealed that her mother had myotonic findings. The baby had 2 brothers and a sister with similar findings at birth. Therefore PCR and Southern blot test was performed on her DNA, obtained from peripheral blood. The test confirmed that she had an allele with more than 1600 CTG repeats on chromosome 19q13.3. Her mother was found to be homozygous for this disease and the number of CTG repeats in the mother was 300. After the mother was diagnosed as a carrier of the disease, all of her offsprings were screened and the diagnoses reached. One of her brothers and one sister, 16 and 20 years old respectively, were mentally retarded, and the number of CTG repeats in each of them were 470. One of her sisters and one of her brothers had died at the age of 3 months and 1 day. One of her brothers, who was 14 years old, was seemingly normal, but he had a shorter allele with 58 repeats. He is expected to manifest the disease later in life. The baby was discharged on the 10th day of life. Although the importance of follow-up was emphasized, the family was lost to follow-up. [(0)] [(1)]