Aarskog-Scott syndrome

Epidemiology

AAS prevalence is not known, but less than 100 cases have been reported in the literature since the first description in 1970. However, prevalence estimates are thought to be around 1/25,000. About 40 molecularly proven cases are published worldwide.

Aarskog-Scott syndrome

Clinical description

AAS predominantly concerns males. Facial features include widow's peak and hypertelorism, both observed in female carriers, and downslanting palpebral fissures, broad nasal bridge, anteversed nostrils, low set and protuberant ears, maxillary hypoplasia and transverse crease below the lower lip. AAS patients have short and broad hands and feet, interdigital webbing, clinodactyly, and hyperextension of proximal interphalangeal joints and flexion at distal interphalangeal joints causing swan neck deformity of fingers. Size is generally normal at birth, but growth is slow in infancy and childhood, leading to short stature until puberty, which is often delayed. A growth spurt in late teens, generally, results in a moderate short stature. Genital anomalies may include cryptorchidism, macroorchidism, shawl scrotum and, more rarely, hypospadias. Fertility is normal. Female carriers may have only a subtle phenotype with hypertelorism and widow's peak. Patients may present a neurodevelopmental phenotype with learning and behavioural disabilities that are often confined to early childhood. When present, mental impairment is rarely severe.

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Plague

Syndromes and synonyms: Pestis, pest, bubonic plague, pneumonic plague, black plague, black death.

Agent: Yersinia pestis, a Gram-negative bacillus. Y. pestis is considered a potential biological warfare agent.

Yersinia pestis (Pasteurella pestis) is the bacterium responsible for the bubonic plague.

Reservoir: Rodents, principally rats and sylvatic ground squirrels: marmots, susliks, and prairie dogs. Rabbits, camels, carnivores, and domestic cats may also be infected. Cats can also develop pneumonic plague. The desert regions of Central Asia contain endemic plague foci where the great gerbil is the main host.

Vector: Fleas, especially the rat flea (Xenopsylla cheopis) and possibly human flea (Pulex irritans).

Transmission: By flea bite for the bubonic form, by the respiratory route for the pneumonic form; handling carcasses or eating meat of infected animals. Person-to-person transmission occurs through the bite of fleas (bubonic form) or respiratory droplets (pneumonic form).

Hand of a plague patient displaying acral gangrene. Gangrene is one of the manifestations of plague and the
origin of the term Black Death given to plague throughout the ages.

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Adamson's fringe

Adamson's fringe is located at the upper margin of the keratogenous zone of the hair follicle where the nucleated hair shaft cornifies completely and gets converted to hard anucleated keratin.

Adamson's fringe

It marks also the area of complete keratinization of the cuticle and Henle's layer of the inner root sheath and the beginning of the stem of the follicle. In Tinea capitis, dermatophytic infection of the hair shaft is restricted to this zone and the fungi do not penetrate further down the infected hair in the bulb of the follicle. The fungi in Adamson's words form “a fringe of mycelium surrounding the hair shaft and project below the lower margin of the sheath of spores around the root-stem.” 

Photomicrograph at level of Adamson's fringe, showing on the right the covering inner root sheath with bright pink trichohyalin granules, and in the centre, mainly anucleate hair shaft with few residual nuclei 

The keratogenous zone of the hair follicle is a broad area above the bulb of the follicle in which the cells are gradually transformed into hard keratin of the hair shaft.

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Botulism

Botulism is a rare but fatal disease caused by botulinum toxins released from Clostridium botulinum bacteria. Botulism is categorized into five different forms: foodborne botulism, wound botulism, infant botulism, inhalation botulism, and iatrogenic botulism.

Botulism is a potentially fatal condition that is caused by a bacterium called Clostridium botulinum.

Agent: Botulinum toxin, produced by the anerobic sporeforming bacterium Clostridium botulinum types A, B, E and rarely F. Type E and F neurotoxins have been recovered from infants with botulism due to C. butyricum and C. barati. C. botulinum is considered a biological warfare agent.

Reservoir: C. botulinum spores are found in soil, dust, honey, marine sediments, and in intestines of fish and land animals.

Transmission: By ingestion of contaminated food (honey in infant botulism), injection of contaminated drugs, or contamination of wounds by soil, dust or gravel. There is no human-to-human transmission.

Clostridium botulinum gram stain.

Incubation period: Usually 12–36 hours; sometimes several days; up to 2 weeks for wound botulism. Clinical findings: Descending flaccid skeletal muscle paralysis beginning at the shoulders in the absence of fever; fatigue, weakness, vertigo, blurred vision, dry mouth, difficulty in speaking and swallowing, progressing to an inability to breathe without assistance. Vomiting, diarrhea or constipation may occur. The CFR in the USA after treatment is 5–10%; recovery may take months. Infants present with constipation, anorexia, weakness, an altered cry, difficulty sucking, and swallowing. Muscle weakness progresses in a symmetric descending fashion over hours to a few days. The prognosis is excellent when treated timely.

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Renin–angiotensin–aldosterone system (RAAS)

 The Renin-Angiotensin-Aldosterone System (RAAS) is a hormone system within the body that is essential for the regulation of blood pressure and fluid balance. The system is mainly comprised of the three hormones renin, angiotensin II and aldosterone. Primarily it is regulated by the rate of renal blood flow.

The renin–angiotensin–aldosterone system (RAAS).

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