Editor,—Hypomelanosis of Ito (HI) is a neurocutaneous syndrome characterised by hypopigmented skin lesions along Blaschko’s lines, frequently associated with neurological, musculoskeletal, ocular, and other extracutaneous manifestations. Chromosomal mosaicism in skin fibroblasts is responsible for approximately 30% of the cases.1 Kearns Sayre syndrome (KSS) is a mitochondrial multisystem disorder, usually associated with a single large scale muscle mtDNA deletion. Its main clinical characteristics are progressive external ophthalmoplegia and pigmentary retinopathy but virtually all organ systems can be involved.2

We report a 13 year old boy who, at the age of 5 years, was diagnosed with HI and who later, at the age of 12 years proved to have KSS. At the age of 5 years the patient had short stature, mild mental retardation, corneal opacities and myopia, irregularly spaced teeth with hypoplastic dental enamel, hypopigmented patchy lesions on the left side of the trunk, and linear streaks on the left limbs. The laboratory investigations were negative for malabsorption disease, endocrine abnormality or metabolic disorder. Skin histology showed decreased melanin in the hypopigmented skin. Karyotype analysis, using G banding technique, in peripheral blood lymphocytes and skin fibroblasts was normal, 46 XY

At the age of 10, he presented with hypocalcaemic tetany. He had also bilateral ptosis of the eyelids, slurred speech, and limb muscle weakness. Parathyroid ultrasound, serum 25(OH)D vitamin, muscle enzymes, tensilon test, and brain magnetic resonance imaging (MRI) were normal. At the age of 12, ophthalmologic examination revealed bilateral limitation of horizontal eye movements. Fundoscopic examination was normal but the electroretinogram was compatible with pigmentary retinopathy. Hearing acquity and cardiac function were normal. The laboratory investigations, relevant to mitochondrial cytopathy showed serum lactate, 2.80 mmol/l (normal 0.33–1.33), serum pyruvate, 0.235 mmol/l (normal 0.33–1.85), cerebrospinal fluid lactate, 7.25 mmol/l (normal 0.33–1.85), cerebrospinal fluid pyruvate, 0.209 mmol/l (normal 0.03–0.08), cerebrospinal fluid protein, 300 mg/dl (normal < 20 mg/dl). Brain MRI showed abnormal signals in the lenticular nuclei. Gomori trichrome stain of quadriceps muscle biopsy demonstrated ragged red fibres; biochemical analysis of mitochondrial enzymes in muscle revealed low cytochrome c oxidase activity. Analysis of muscle mtDNA showed a large scale deletion (5 kb).

The wide spectrum and severity of manifestations of HI as well as its genetic heterogeneity led several authors to believe that HI is not a single clinical entity.3 As far as we know, hypopigmented skin lesions have not been described in KSS but they might have been overlooked. It must be noted that except for external ophthalmoplegia and hypoparathyroidism, all other extracutaneous abnormalities of our patient could be found in KSS as well as in HI.4 Although one case could be a chance association, we suggest that KSS or other mitochondrial disorders should be suspected in patients fulfilling the criteria of HI.