Diagnosis of dystrophinopathy by skin biopsy

Skin Biopsy for Diagnosis of Ullrich Congenital Muscular Dystrophy: An Observational Study

The gold standard diagnostic test for Ullrich congenital muscular dystrophy (UCMD) is molecular testing for COL6 mutation. The facility for genetic testing is sparingly available and it is usually diagnosed by muscle biopsy. The latter is an invasive procedure requiring expertise and sedation. Skin biopsy has shown promise as a simpler diagnostic modality. Eleven and 7 cases, respectively, of phenotypically suspected Ullrich congenital muscular dystrophy and dystrophinopathy underwent simultaneous skin and muscle biopsies, which were subjected to hematoxylin and eosin (H&E) and immunohistochemistry staining for collagen VI and dystrophin 1, 2, and 3. Of the 8 and 5 muscle biopsy-confirmed cases of Ullrich congenital muscular dystrophy and dystrophinopathy, 6 Ullrich congenital muscular dystrophy and 5 dystrophinopathy cases showed absent and preserved COL6 staining, respectively, in the skin biopsy. Skin biopsy as a diagnostic option has shown encouraging results in Ullrich congenital muscular dystrophy. These should be evaluated in larger studies.

Skin biopsy: a new tool to diagnose sarcoglycanopathy

Muscular dystrophies are progressive, genetic disorders of muscle degeneration. The current gold standard for diagnosis is muscle biopsy or genetic studies. Muscle biopsy is an invasive procedure and genetic testing facilities are available only in a few centers. Thus, a diagnostic test that is easily available, simpler, and less invasive is desirable. Over the past 2 decades, skin biopsy has been evolving as a suitable option. Two cases of sarcoglycanopathy are described here, which have been correctly diagnosed by skin biopsy. Muscle biopsy has been used as the gold-standard diagnostic method. Skin biopsy can substitute for muscle biopsy as the preliminary diagnostic tool directing appropriate molecular testing. However, these results require validation in studies with an adequate sample size. This holds promise for the future when repeated biopsies will be required for evaluating protein rescue in trials of novel treatment options in these disorders.

Dystrophinopathy diagnosis made easy: skin biopsy, an emerging novel tool

Dystrophinopathies are diagnosed by genetic studies and muscle biopsy. Most centers have multiplex polymerase chain reaction facilities diagnosing 65% to 70% of dystrophinopathy cases. Muscle biopsy is a time-consuming, invasive procedure whereas skin biopsy is a simple procedure done under local anesthesia. The current study evaluated the diagnostic accuracy of skin biopsy in dystrophinopathy. Overall, 119 confirmed cases of muscular dystrophy (111 males and 8 females) were included in the final analysis, of which 100 (all males) were dystrophinopathy. Skin biopsy diagnosed dystrophinopathy in suspected muscular dystrophy patients with a sensitivity of 98% (92.3%-99.7%), specificity of 99% (93.7%-99.9%), positive predictive value of 94.7% (71.9%-99.7%), and negative predictive value of 90% (66.9%-98.2%). Skin biopsy can be used for screening dystrophinopathy in muscular dystrophy patients (high sensitivity and positive predictive value). It being a simple and minimally invasive procedure, histopathologic and molecular markers of disease progression and response to novel treatment options can be assessed serially.

[Normal skin biopsy as a tool for extra-cutaneous disorders]

Biopsies of apparently healthy skin can contribute to the diagnosis of an internal disorder in a patient or in the detection of a potential disease carrier. Herein, we review those diseases for which dermatologists may be asked to perform a biopsy on normal skin where analysis by optical microscopy, immunofluorescence or electronic microscopy may result in diagnosis of an "internal" disease. Diseases for which biopsies are required for cell cultures (e.g. fibroblasts cultures), clonality testing or chromosomal analysis are not discussed here.

[Changes in clinical condition and causes of death of inpatients with Duchenne muscular dystrophy in Japan from 1999 to 2012]

To elucidate changes in medical treatment for Duchenne muscular dystrophy (DMD) in Japan, we analyzed the clinical courses and causes of death of inpatients with DMD registered in the muscular dystrophy ward database of 27 hospitals in Japan specializing in muscular dystrophy treatment since 1999. The total number of hospitalized cases in 1999 was 873, which gradually reduced to 733 in 2012. The mean age of DMD patients in 1999 was 23.6 years old, while that was 30.1 years old in 2012, with patients 40 years and older accounting for 94 cases in the latest year. The respirator dependent rate gradually increased from 58.6% in 1999 to 86.1% in 2012. Artificial respiration therapy was introduced earlier in more recent years and the mean age in recent years was shown to be 17.2 years old. The oral nutritional supply rate in 1999 was 95.1%, which fell to 66.8% in 2012, while gastrostomy feeding gradually increased to 129 cases in 2012. The rate of clinical diagnosis of DMD was 52.3% in 1999 and decreased to 43.7% in 2012, which showed progress towards more accurate diagnosis of DMD. From 2000 to 2012, 521 deaths were reported, with approximately half of the causes heart related, followed by respiratory related. The mean age of death gradually increased to 32.4 years old in 2012 from 26.7 years old in 2000. The mean age of survival of all DMD patients was 37.5 years old. Progress in multidisciplinary medical care for respiratory failure, cardiomyopathy, nutritional problems, and other related factors has extended the lifespan of DMD patients.

[A longitudinal cause-of-death analysis of patients with Duchenne muscular dystrophy]

Mechanical ventilation (MV) and cardiac protective therapy have improved the prognosis and quality of life of patients with Duchenne muscular dystrophy (DMD). To understand how these therapies have changed prognosis, we performed a cause-of-death analysis in DMD patients. Mean age at death before initiation of MV (January 1977-July 1984) was 18.9±4.1 years. After the introduction of MV, from August 1984 to December 1993 (1(st) term), it was 20.0±4.5 years, from January 1994 to December 2003 (2(nd) term), it was 25.2±4.6 years, and from January 2004 to December 2010 (3(rd) term), it was 31.1±5.4 years. Almost half of all deaths before MV were due to respiratory failure (RF). Because MV was performed by a tracheostomy in the initial stage, some patients were reluctant to use it, and as a result, RF accounted for 43% of deaths in the 1(st) term. Over time, patients started to accept non-invasive ventilation and home mechanical ventilation, which became available in the 1990s. Consequently, no DMD patients have died from RF since 2000. Respiratory physiotherapy and risk management became important tools, because many patients undergo decades of respiratory managements at home. Cardiac treatments for patients with DMD consisted mainly of diuretics and digitalis in the 1(st) term, angiotensin-converting enzyme inhibitors (ACEI) in the 2(nd) term, and a combination of ACEIs and beta blockers in the 3(rd) term. Compared to the 2(nd) term, the ratios of severe cardiac dysfunction (fractional shortening <10%, left ventricle diastolic dimension >75mm, plasma brain natriuretic peptide >1,000pg/ml) were reduced in the 3(rd) term. In the 3(rd) term, 14% of patients died from renal failure nevertheless their cardiac indices remained mildly abnormal or normal. We should pay enough attention for cardio-renal association.

Perioral skin biopsy to study skeletal muscle protein expression

Clinical trials for muscular dystrophy molecular treatment require multiple sampling of skeletal muscle to monitor protein rescue. This practice is invasive and could raise ethical problems. A less invasive tool to obtain sequential muscle sampling is necessary. Using indirect immunofluorescence, we evaluated muscle protein expression in myofiber bundles included in 2-2.5-mm punch skin biopsies from the perioral region from 6 healthy subjects and 6 patients with genetically defined forms of muscular dystrophy. Large intradermal bundles of orbicularis oris muscle were constantly present in skin biopsies. They showed a typical muscular antigenic pattern in controls and the expected protein defect in muscular dystrophy patients. These results demonstrate the feasibility of muscular protein expression analysis using skin biopsy. We propose this minimally invasive technique to follow-up the response to genetic or conventional therapies in muscular dystrophies and to confirm the diagnosis in some special clinical conditions.

Diagnostic Immunohistology of Muscle Diseases

The diagnostic muscle biopsy has seen the use of virtually every histologic technique in existence over the past 50 years. Since the 1960s, enzyme histochemistry has become the chief technique in evaluating muscle biopsies. However, the increasing knowledge of cellular constituents and associated connective tissue of the myofiber coupled with the increasing availability of a broad diversity of antibodies to these proteins promises to bring the diagnosis of muscle disease to the same state of dependency upon immunohistochemistry as in the contemporary pathologic diagnosis of neoplasia. Immunohistochemistry may be used for both the identification of normal antigenic constituents in skeletal muscle and their loss, accumulation, or maldistribution in corresponding myopathies, sometimes with small biopsies or lacking frozen tissue, in paraffin sections. Three broad categories of muscle diseases will be characterized in terms of diagnostic antibodies in current use: dystrophic, congenital/structural, and inflammatory myopathies.