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L J Ptacek

Publications and source records attributed to L J Ptacek.

27 records · Page 2Linked to original sources
PubMed1992

Linkage of atypical myotonia congenita to a sodium channel locus.

We performed linkage analysis in a pedigree segregating an allele for autosomal dominant, painful myotonia that is potassium sensitive and responsive to acetazolamide. This allele was tightly linked to a skeletal-muscle, sodium channel locus which is now a candidate for the site of the mutational defect in acetazolamide-responsive myotonia congenita. Since this sodium channel locus is completely linked to the disease allele in all hyperkalemic periodic paralysis and paramyotonia congenita pedigrees studied, the molecular alteration causing acetazolamide-responsive myotonia congenita is likely an allelic defect in this human, skeletal-muscle, sodium channel gene.

Chromosome Mapping↗
PubMed1992

Evidence of genetic heterogeneity among the nondystrophic myotonias.

Recent in vitro electrophysiologic studies have demonstrated abnormal sodium channel gating in muscle from patients with Thomsen's disease and have called the chloride hypothesis into question. Abnormal sodium channel function, like myotonia, is a feature common to Thomsen's disease and several myotonias that are genetically linked to a chromosome-17q sodium channel locus. We present a pedigree segregating an allele for Thomsen's disease that is unlinked to this sodium channel locus, thus constituting evidence of genetic heterogeneity among the nondystrophic myotonias.

Child↗
PubMed1991

Analysis in a large hyperkalemic periodic paralysis pedigree supports tight linkage to a sodium channel locus.

Hyperkalemic periodic paralysis (HYPP) is an autosomal dominant muscle disease with electrophysiological abnormalities suggesting a defect in a voltage-gated sodium channel (NaCh) gene. A human NaCh gene was recently shown to cosegregate with the disease allele in a family with HYPP. Using an independent clone, we have demonstrated close genetic linkage between an NaCh gene and the HYPP locus in another family. With physiological data demonstrating abnormal NaCh function in HYPP patients, the absence of any obligate recombinations in the two families strengthens the argument that this NaCh gene is the site of the defect in this disorder.

Adult↗
PubMed1991

Paramyotonia congenita and hyperkalemic periodic paralysis map to the same sodium-channel gene locus.

Paramyotonia congenita (PC), an autosomal dominant muscle disease, shares some clinical and electrophysiological similarities with another myotonic muscle disorder, hyperkalemic periodic paralysis (HYPP). However, clinical and electrophysiologic differences allow differentiation of the two disorders. The HYPP locus was recently shown to be linked to a skeletal muscle sodium-channel gene probe. We now report that PC maps to the same locus (LOD score 4.4, theta = 0 at assumed penetrance of .95). These linkage results, coupled with physiological data demonstrating abnormal sodium-channel function in patients with PC, implicate a sodium-channel gene as an important candidate for the site of mutation responsible for PC. Furthermore, this is strong evidence for the hypothesis that PC and HYPP are allelic disorders.

DNA Probes↗
PubMed1988

Trochlear nerve palsy following minor head trauma. A sign of structural disorder.

Trauma-induced superior oblique palsy usually results from contusion or avulsion of the trochlear nerve or from decompensation of a congenital trochlear nerve palsy. Severe craniocerebral trauma is often associated with the former mechanism, whereas more minor closed-head injuries can decompensate a congenital phoria. We report a patient who developed an isolated trochlear nerve palsy following minor head trauma. Investigation revealed an unsuspected tentorial vascular malformation that was compressing the trochlear nerve in its subarachnoid course. In the absence of other features (e.g., documentation of old head tilt, large vertical fusion amplitudes) that support decompensation of a congenital phoria, compressive lesions should be sought in cases of fourth cranial nerve palsies that follow minor head trauma.

Cranial Nerve Diseases↗
PubMed1977

Immunological studies on an aberrant form of ataxia telangiectasia.

We describe two brothers with ataxia telangiectasia (AT) of which one was unique in that he had no detectable IgG and IgA concentrations in the serum or saliva. The other brother had the more common IgA deficiency in the serum and saliva. Neither patient had a history of undue sinopulmonary infections. In spite of the absence of these immunoglobulins in the sera, there were cells in the bone marrow and peripheral blood that stained with fluorescein-labeled anti-IgG and anit-IgA. Both patients had demonstrable humoral antibody and cell-mediated immune responses to the antigens tested. We also discuss possible pathophysiological mechanisms causing the above defects.

Adult↗