Thursday, May 17, 2018

Interpreting Pedigree chart to recognize pattern of inheritance


One of the problem faced by students is solving a pedigree chart and recognizing pattern of inheritance, which is even important in day to day clinical practice.

Inheritance that needs to be differentiated in pedigree can be

Mendelian ( Single Gene defect )
 Autosomal Dominant
Autosomal Recessive
X linked

Non traditional inheritance like
Mitochondrial inheritance

In a Step Wise approach

1. Identify whether pattern of inheritance is Autosomal or Sex linked.
If only Males are affected , it is likely X linked inheritance ( Recessive, X linked dominant disorders are very rare)
If both males and females are equally affected, it is Autosomal inheritance


2. Determine whether the disorder is dominant or recessive.
If only Affected parent transmit the disease , it is Dominant disorder
If non-affected parent transmit the disease, it is Recessive disorder.
In other words,
If the disorder is dominant, one of the parents must have the disorder.
If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous.

If disease skips generations, it is likely Recessive disorder.



Rules of Inheritance: Understanding Mendelian disorder by Dr Sulabh Shrestha

Understanding Mendelian inheritance - Epomedicine



Tuesday, May 1, 2018

Umbilical Infection in Neonate leading to Septic shock: Case


A Preterm neonate of 33 weeks gestation deteriorated on day 2 with septic shock and decreased urine output rapidly over 12 hours. Baby was pale and CRT was prolonged. A Workup was sent and Emperical Antibiotics were started. Baby needed Inotrope support and improved over next 24-48 hours. On day 4, redness was seen around umbilical area and was indurated and tender on palpation.
A diagnosis of Omphalitis was made, Swab culture was sent from the base of cord and Cloxacillin was added. Local dressing was done and local antiseptic ointment was applied.



Over next 2 days, the redness decreased along with induration. Umbilical stump still had not fallen off . Treatment was continued.



After the cord fell off, the redness and induration subsided but pus discharge was seen as umbilicus was manipulated everytime.  Swab culture was sent. As abdomen was distended, an sonogram of abdomen was done to look for internal extension, including screening for collection in fascia and liver. USG was normal. Inj Vancomycin was added and cloxacillin was stopped.


Finally, baby showed drastic improvement. Distension of abdomen subsided and umbilicus looked healthy.  Finally baby was discharged. Although no cultures were positive, empirical antibiotics for  Staph aureus was administered for 14 days duration.




Discussion

Although Omphalitis is superficial infection of umbilical cord, a dreaded scenario is when there is rapid extension of infection to fascia, muscles and peritoneum of abdomen leading to necrotizing fascitis, myonecrosis and peritonitis. Systemic spread can lead to sepsis and shock rapidly like in this condition. Common organism leading to this conditions are Staph aureus, Streptococcus and gram negative organisms like Klebsiella and Proteus. MRSA are reported in cases of omphalitis. Application of dung, human milk and herbs to cord can lead to infection by Clostridium.

Risk factore for Omphalitis, include Septic delivery, PROM, chorioamnionitis, umbilical vessel catheterization which were all absent in this case. Baby was Low birth weight and was another risk factor for omphalitis. 

Mean age of onset in preterm is 3-5 days and in term babies it is 5-9 days.

Treatment:
A combination therapy for Gram +ve and -ve agents
Inj Vancomycin and an aminiglycoside is preferred drug for emperical use.
If extension to internal structure is suspected addition of metronidazole or clindamycin may be needed.

Surgical consultation for complicated cases.


Complications:
Necrotizing fascitis
Myonecrosis
Pertitonitis and abdominal abscess
Liver abscess
Portal vein thrombosis.